VT43N3 - PerkinElmer Optoelectronics

Photoconductive Cells and

Analog Optoisolators (V

Analog Optoisolators (Vactrols®)

actrols®)

Sensors

Telecom

Digital Imaging

Specialty Lighting

Lighting Imaging Telecom Sensors

Detectors and Sensors

Optoelectronics

Optoswitches, optical hybrids, custom assemblies, photodiodes, phototransistors, IR

emitters, and photoconductive cells for industrial, commercial, and consumer electron-

ics applications.

PerkinElmer Optoelectronics has the distinction of being one of the foremost manufacturers in

optoelectronics. Founded in 1947, PerkinElmer offers its customers over 35 years experience

in the development and application of optoelectronic devices. The product line is one of the

broadest in the industry, including a variety of standard catalog products as well as custom

design and manufacturing capabilities. Approximately 75% of the products shipped are cus-

tom designed and tested to serve the needs of specific OEM applications.

Three basic objectives guide PerkinElmer ’s activities - Service, Quality, and Technology.

Our outstanding engineering staff, coupled with the implementation of modern material control

and manufacturing techniques, plus our commitment to quality, has gained PerkinElmer “certi-

fied” status with many major customers. Products are often shipped directly to manufacturing

lines without need for incoming QC at the customer ’s facility. PerkinElmer ’s products are verti-

cally integrated, from the growing of LED crystals, silicon die fabrication, package design, reli-

ability qualification, to assembly. Vertical integration is your assurance of consistent quality.

Recognizing the need for low-cost manufacturing to serve world markets, PerkinElmer

expanded its manufacturing/assembly operations into the Far East more than 20 years ago.

The combination of strong technology in processing at the St. Louis headquarters and low-

cost assembly operations in the Far East has allowed PerkinElmer to effectively serve all

markets, worldwide. PerkinElmer provides optical sensors, IR emitters and subassemblies for

such diverse applications as street light controls, cameras, smoke alarms, business

machines, automotive sensors, and medical equipment.

For pricing, delivery, data sheets, samples, or technical support please contact your

PerkinElmer Sales Office or direct your questions directly to the factory.

PerkinElmer Optoelectronics

10900 Page Avenue

St. Louis, Missouri 63132 USA

Tel: (314) 423-4900 Fax: (314) 423-3956

PerkinElmer Optoelectronics

www.perkinelmer.com/opto

i
Table of Contents
Photoconductive Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
What is a Phot oco nductive Cell ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Phot oc onductive Cell Typical Appli cat ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Why Use Photocells?   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Phot oconducti ve Cell  Typical Appli cat ion Ci rcuits  .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Selecting a Photocell  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Phot oconducti ve Cell  Typical Cha rac teristic Cur ves @ 25°C Type Ø Materi al  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Type Ø Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Phot oconduct ive Cell  Typical Cha racteristi c Cur ves @ 25°C Type 3 Materi al   . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Type 3 Material  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Phot oc onductive Cell  Tes ting and Genera l Note s .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Production Testing of Photocells - PerkinElmer’s New Approach  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Device Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Plastic Coated
VT900 Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
VT800 Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
VT800C T Ser i es  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
VT400 Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Glass/Metal (Hermetic) Case
VT200 Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
VT300 Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
VT300C T Ser i es  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
VT500 Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Appli cation Not es—P hotoconductive Ce lls  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
APPLICATION NOTE #1 Light - Some Physical Basics  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
APPLICATION NOTE #2 Light Resistance Measurement Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
APPLICATION NOTE #3 Spectral Output of Common Light Sources  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
AP PLICA TION NOTE #4 Spect ralMatching ofLE Dsand Photoconductive Types  . . . . . . . . . . . . . . . . . . . . . 24
APPLICATION NOTE #5 Assembly Precautions  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
APPLICATION NOTE #6 A Low Cost Light Source for Measuring Photocells  . . . . . . . . . . . . . . . . . . . . . . . . . 25
APPLICATION NOTE #7 How to Specify a Low Cost Photocell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

ii
Table of Contents (Continued)
Analog Optical Isolators VACTROLS®  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
What Are Analog Optical Isolators?  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Typical Applications of Analog Optical Isolators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Characteristics of Analog Optical Isolators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Transfer Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Response Time  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Noise  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Distortion  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Voltage Rating  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Power Rating  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Life and Aging  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Storage Characteristics  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Tempe rat ure Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Typical Transfer Characteri stics (Resistance vs.  Input  Current) For  Standard Vactrol s  . . . . . . . . . . . . . . . . . . 40
Analog Optoisolator Comparison Chart  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Device Specifications
VTL5C1, 5C2  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
VTL5C3, 5C4  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
VTL5C2/2, 5C3/2  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
VTL5C4/2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
VTL5C6, 5C7  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
VTL5C8  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
VTL5C9, 5C10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Application Notes—Analog Optical Isolators  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
APPLICATION NOTE #1 Audio Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
APPLICATION NOTE #2 Handling and Soldering AOIs  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7
AP PLICA TION NOTE #3 Recom m ended Cleani ngA gents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

iii

Custom and Se mi-Custom Devices

Upon request, and where sufficient quantities are involved,

PerkinElmer Optoelectronics will test standard parts to your

unique set of specifications. The advantage of testing parts

under actual operating conditions is predictable performance in

the application.

PerkinElmer offers a broad line of standard photodiodes in a

wide variety of packages and sensitivities. Nevertheless, some

applications demand a totally custom device. Recognizing this

real need, PerkinElmer’s engineering, research, and sales

departments are geared for working with the customer from

in itial co ncep t thr ough des ign, prot oty pe, a nd v olum e pr od uct ion.

A custom design usually required the commitment of valuable

resources. Perk inElmer reviews reques ts for custom devices on

a case by case basis and reserves the right to decide if the

business potential warrants the undertaking of such a project.

The customer may be asked to share in the expense of

development.

PerkinElmer has designed and fabricated custom products for

many companies. PerkinElmer’s staff can work closely with the

customer and protect proprietary information. A custom design

usually required the commitment of valuable resources.

PerkinElmer reviews requests for custom devices on a case by

case basis and reserves the right to decide if the business

potential warrants the undertaking of such a project. The

custome r may be ask ed to sh ar e in the expe nse of dev elopment.

PerkinElmer has designed and fabricated custom products for

many companies. PerkinElmer’s staff can work closely with the

custome r and protect pr oprietary inf ormation.

Your inquiries to PerkinElmer should include electrical,

environmental, and mechanical requirements. Also, information

on anticipated volumes, price objectives, and lead times is

helpful since these often determine the choices of design and

tooling.

Photoconductive Cells

What is a Photocondu ctive Cell?

Semiconductor light detectors can be divided into two major

categories: junction and bulk effect devices. Junction devices, when

operated in the photoconductive mode, utilize the reverse

characteristic of a PN junction. Under reverse bias, the PN junction

acts as a light controlled current source. Output is proportional to

incident illumination and i s relativel y independent of implied voltage as

shown in Figure 1. Silicon photodiodes are examples of this type

detector.

Figure 1

Junction Photoconductor (Photodiode)

Figure 2

Bulk Effect Photoconductor (Photocell )

In contrast, bulk effect photoconductors have no junction. As shown in

Figure 2, the bulk resistivity decreases with increasing illumination,

allowing more photocurrent to flow. This resistive characteristic gives

bulk effect photoconductors a unique quality: signal current from the

detector can be varied over a wide range by adjusting the applied

voltage. To clearly make this distinction, PerkinElmer Optoelectronics

refers to it’s bulk effect photoconductors as photoconductive cells or

simply photocells.

Photocells are thin film devices made by depositing a layer of a

photoconductive material on a ceramic substrate. Metal contacts are

evaporated over the surface of the photoconductor and external

electrical connection is made to these contacts. These thin films of

photoconductive material have a high sheet resistance. Therefore, the

space between the two contacts is made narrow and interdigitated for

low cell resistance at moderate light levels. This construction is shown

in Figure 3.

Figure 3

T ypical Construction of a Plastic Coated Photocell

Photoconductive Cell Typical Applications

Why Use Photocells?

Photocells can provide a ver y economic and technically superior solution for many appl ications where the presence or absence of light is sensed

(digital operation) or where the intensity of light needs to be measured (analog operation). Their general characteristics and features can be

summ arized as follows:

• Lo w est cos t available and near -IR p hot o detector

• Available in low cost plastic encapsulated packages as well as hermetic packages (TO-46, TO -5, TO -8)

• Responsive to both very low lig ht lev els (moonlight) and to very high light le vels (direct sunlight)

• Wide dynamic range: res ist ance ch anges o f sever al orders of magn it ude betwee n " li ght" a nd "no light"

• Low noise dist ortion

• Maximum op er ating voltages of 50 to 400 volts are sui table for operat ion on 120/240 VAC

• Available in cent er tap dual cell configurations as w ell as specially sel ected resistance rang es for spe c ial applic ati ons

• Easy to use in D C or AC circuits - they are a ligh t variab le resistor and hence symmet rical with respect to AC wavef orms

• Usable with almost any visi ble or nea r infrared light s our ce such as LEDS; neon; fl uor escent, inc andescent bulbs, lase r s ; flame sources;

sunlight; etc

• Av ail able in a wi de r ange of resistance values

Applications

Photoconductive cells are used in many different types of circuits and appl ications.

Analog Appli cations

• Camera Exposure Control

• Auto Sl ide Focus - dual cell

• Phot ocopy Machines - densi ty of ton er

• Col ori metric Test Equipme nt

• Densitometer

• Electronic Scales - dual cell

• Automatic G ain Con tr ol - modulated light source

• Automated R ear View Mirror

Digital Applications

• Automatic H eadlight Dimmer

• Night Light Control

• Oil Burne r Fl am e Out

• Street Light Cont r ol

• Absence / Presence ( beam breaker)

• Positi on Sensor

Photoconduc tive Cell Typical Application Circuits

Ambient Light Measurement

Camera Ex pos ure Met er (V T90 0 )

Br i ghtness Control (V T9 00)

DC Relay

Rear Vie w Mirror Control (VT200)

Head Light Dimmer (VT300 or VT800)

AC Rel a y

N i ght Lig ht Control (VT800 or VT900)

Street L ig h t Control (VT40 0)

Flame Detector (VT400 or 500)

Object Sensing / Measure ment

Beam Breaking Applications (VT800)

Security Systems (VT800 or VT900)

C ol orimet ri c Te st Equi pment (VT200 o r VT300)

D ensit ometer ( V T20 0 or VT300)

Bridge Circuits

A uto Focus (VT300CT or VT800CT)

Electron i c Scal es ( VT 300CT or VT800C T)

Ph otoelec t ri c Servo (VT 300CT or VT800CT)

Selecting a Photocell

Specifying the best photoconductive cell for your application requires

an understanding of its principles of operation. This section reviews

some fundamentals of photocell technology to help you get the best

b lend of param eters f or your application.

When selecting a photocell the design engineer must ask two basic

questions:

1. Wh at kind of performance is required f ro m the cel l?

2. What kind of environm ent must the cell work in?

Per for mance Crite ria

Sensitivity

The sensi tivity of a photodetector is the r elationship between the light

falling on the device and the resulting output signal. In the case of a

ph otocel l, one is deali ng with the rela tionsh ip betw een the in cident ligh t

an d the corresponding resistance of the cell .

Defining the sensitivit y required for a specific application can prove to

be one of the more difficult aspect s in specifying a photoconductor. In

order to specify the sensitivity one must, to some degree, charact erize

the light source in terms of its intensity and its spectral content.

Within this handbook you will find curves of resistance versus light

intensity or illuminatio n for many of Perkin El m er ’s stock photocell s . The

illumination is expressed in units of fc (foot candles) and lux. The light

source is an incandescent lamp. This lamp is special only in that the

spectral composition of the light it generates matches that of a black

body at a color temperature of 2850 K. This type of light source is an

industry agreed to st andard.

Over the years PerkinElmer has developed different “types” of

ph ot oconductive materials through modification s ma de to the chem ical

composition of the detector. For a given type of photoconductor

material, at a given level of illumination, the photoconductive film will;

have a certain sheet resistivity. The resistance of the photocell at this

light level is determined by t he electrode geometry.

(w / l )

where:

= resistance of cell at light

level H

= sheet resistivity of

photoconductive film at light level

w = widt h of electrode gap

l = length of electrode gap

Sheet sensitivity (

) for

ph ot oconductive films at 2 fc are in the range of 20 M

Ω

pe r squ ar e.

The ratio w / l can be varied over a wide range in order to achieve

design goals. Typical values for w / l run from 0.002 to 0.5, providing

flexibility for terminal resistance and maximum cell voltage.

Spectral Response

Like the human eye, the relative sensitivity of a photoconductive cell is

dependent on the wavelength (color) of the incident light. Each

photoconductor material type has its own unique spectral response

curve or plot of the relative response of the photocell versus

wav elength of light.

The spectral response curves for PerkinElmer’s material types are

given in the handbook and should be considered in selecting a

ph ot ocell for a particul ar applicati on.

Selecting a Photocell

Slo pe Characteristics

Plots of the resistance for the photocells listed in this catalog versus

lig ht intens ity result in a series of curv es with char acterist icall y diff eren t

slopes. This is an important characteristic of photocells because in

many applications not only is the absolute value of resistance at a

given light level of concern but also the val ue of the resistance as the

light source is varied. O ne way t o specify this relat ionship is by the use

of parameter (gamma) which is defined as a straight line passing

through two specific points on the resistance curve. The two points

used by PerkinElmer to define

are 10 lux (0.93 and 100 lux (9.3

fc).

Applications for photocells are of one of two categories: digital or

analog. For the digital or ON-OFF types of applications such as flame

detectors, cells with steep slopes to their resistance versus light

intensity curves are appropriate. For analog or measurement types of

applications such as exposure cont rols for cameras, cells with shallow

slopes might be better suite d.

Resistance Tol erance

The sensitivity of a photocell is defined as its resistance at a specific

level of illumination. Since no two photocells are exactly alike,

sensitivity is stated as a typical resistance value plus an allowable

tolerance. Both the value of resistance and its tolerance are specified

for only one light level. For moderate excursions from this specified

light level the tolerance level remain more or less constant. However,

when the light level the tolerance level remain more or less constant.

However, when the light level is decades larger or smaller than the

reference level the tolerance can differ considerably.

As the light level decreases, the spread in the tolerance level

increases. For increasing light levels the resistance tolerance will

tighten.

Likewise, for dual element photocells the matching factor, which is

defined as the ratio of the resistance of between elements, will

incr ease with dec re asing light level.

Dark Resistance

As the name implies, the dark resistance is the resistance of the cell

under zero illumination lighting conditions. In some applications this

can be very important since the dark resistance defines what

maximum “leakage current” can be expected when a given voltage is

applied across the cell. Too high a leakage current could lead to false

triggering in some appl ications.

The dark resistance is often defined as the minimum resistance that

can be expected 5 seconds after the cell has been removed from a

ligh t intens ity o f 2 fc. Typical v alues fo r dark resist ance tend to be in the

500k ohm to 20M ohm range.

Tempe rature Coefficient of Res ist ance.

Each type of photoconductive material has its own resistance versus

temperature characteristic. Additionally, the temperature coefficients of

photoconductors are also dependent on the light level the cells are

operating at.

From the curv es of the various types of materi als it is apparent that t he

temperature coeff ic ien t is an inv erse funsti n of li ght le vel . Thus, in order

to minimize temperature problems it is desirable to have the cell

op er ating at the highest light level possible.

Speed of Response

Speed of response is a measure of the speed at which a photocell

responds to a change from light-to- dark or from dark-to-light. The r ise

time is defined as the time necessar y for the light conductance of the

ph ot ocell to reac h 1- 1/e (or about 63%) of its final value.

γLog Ra Log Rb–

Log a Lob b–

-------------------------------------=

Log Ra Rb⁄()

Log b a⁄()

------------------------------=

Dual Element Photocell Typica l Matching Ratios

0.01 fc 0.1 fc 1.0 fc 10 fc 100 fc

0.63 – 1.39 0.74 – 1.27 0.75 – 1.25 0.76 – 1.20 0.77 – 1.23

Selecting a Photocell

The decay or fall time is defined as the time necessary for the light

conductance of the photocell to decay to 1/e (or about 73%) of its

ill um inated st ate. A t 1 fc of illum ination the respo nse times ar e typically

in t he range of 5 msec to 100 msec.

The speed of response depends on a number of factors including light

level, light history, and ambient temperature. All material types show

faster speed at higher light levels and slower speed at lower light

levels. Storage in the dark will cause slower response than if the cells

are kept in the light. The longer the photocells are kept in the dark the

more pronounced this effect will be. In addition, photocells tend to

respond slow er in colder temperatures .

Light History

All photoconductive cells exhibit a phenomenon known as hysteresis,

light memory, or light history effect. Simply stated, a photocell tends to

remember its most recent storage condition (light or dark) and its

instantaneous conduct ance is a function of its previous condition. The

magnitude of the light history effect depends upon the new light level,

and upon the time spent at each of these light levels. this effect is

reversible.

To understand the light history effect, it is often convenient to make an

an alogy between t he re sponse of a photocell and that of a human eye.

Like the cell, the human eye’s sensitivity to light depends on w hat level

of light it was recently exposed to. Most people have had the

experience of coming in from the outdoors on a bright summer’s day

and being temporarily unable to see under normal room levels of

illumination. your eyes will adjust but a certain amount of time must

elapse first. how quickly one’s eyes adjust depends on how bright it

was outside and how long you remained outdoors.

The following guide shows the general relationship between light

history and light resistance at various light levels. The values shown

were determined by dividing the resistance of a given cell, following

infinite light hi st ory (R

), by the resistance of the same cell following

“infinite” dark history (R

). For practical purposes, 24 hours in the

dark wi ll a chieve R

or 24 hours at approximately 30 fc will achieve

T ypical V a riation of Resistance with Light History Expressed as a Ratio

RLH /

RDH

at Various Test Illumination Levels.

This guide illustra tes the fact that a photocell whi ch has been stored for

a long tim e in the light will have a considerably higher light resistance

than if it was stored for a long time in the dark. Also, if a cell is stored

for a long per iod of time at a light level higher than the test level, it will

ha ve a higher light resist ance than if it was st or ed at a lig ht l evel closer

to the test light level.

This effect can be minimized significantly by keeping the photocell

exposed to some constant low level of illumination (as opposed to

having it sit in the dark). This is the reason resistance specifications

are characteri zed after 16 hour s light adept.

En vir onmental/Circuitry Considerations

Packaging

In order to be protected from potentially hostile environments

photocells are encapsulated in either glass/metal (hermetic) package

or are covered with a clear plastic coating. While the hermetic

packages provide the greatest degree of protection, a plastic coating

represents a low er cost approach.

The disadvantage of plastic coatings is that they are not an absolute

bar rier to event ual penetration by moisture. This can have an adverse

effect on cell life. However, plastic coated photocells have been used

successfully for many year s in such hostile en vironments as street light

controls.

Temper ature Range

The chemistry of the photoconductive materials dictates an operating

and storage temperature range of –40°C to 75°C. It should be noted

that operation of the cell above 75°C does not usually lead to

cat ast rophi c failure but the photoconductive surface may be damaged

leading to irr eversible changes in sensitivity.

The amount of resistance change is a function of time as well as

temperature. While changes of several hundred percent will occur in a

matter of a few minutes at 150°C, it will t ake years at 50°C to produce

that m uch change.

Power Dissipation

During operatio n, a cell must remain within its maximum inter nal

temperature rating of 75°C. Any applied power will raise the cell’ s

temperature above ambient and must be considered.

Illumination

RLH / RDH

Ratio 0.01 fc 0.1 fc 1.0 fc 10 fc 100 fc

1.55 1.35 1.20 1.10 1.10

Selecting a Photocell

Many low voltage situations involve very little power, so that the

photocell can be small in size, where voltages and/or currents are

higher, the photocell must be physically larger so that the

se miconductor f ilm can dissipate the heat.

The following curve of power dissipation versus ambient temperature

describes the entire series of cells for operation in free air at room

ambient (25°C). Note that regardless the size, all photocells derate

linearly to zero at an ambient temperat ure of 75°C. The adequate heat

sinks can increase the dissipati on by as much as four times the level s

shown in this graph.

Maximum Cell Voltage

At no time should the peak voltage of the cell exceed its maximum

voltage. the designer should determine the maximum operating or

peak voltage that the cell will experience in the circuit and choose an

ap pr opri ately r ated cell. Typical voltage r ates r ange from 100V to 30 0V.

What Type of Material is Best?

Each specific material type represents a trade off between several

characteristics. Selecting the best m ater ial is a pr ocess of determining

which character istics ar e most important tin the application.

PerkinElmer’s standard photocells in this catalog are manufactured

using one of two di ffer ent material types offered: type “Ø” or type “3”.

In general, material type “Ø” is used for applications such as

nightlights, automotive sensors. Material type “3” is primarily used in

ca mera, street li ght control, and flame detector application s.

Photoconductive Cell Typical Characteristic Curves

@ 25°C Type Ø Material

Type Ø Material

This is a general purpose material. Its characteristics include a good temperature coefficient and fast response time, especially at very

low light leve ls. Cells of this type h ave rel ati vely low dark history. Ty pe Ø mater ia l is ofte n used in lighti ng contro ls such as nightlight s,

and security lighting.

The resistance for any standard catalog cell is controlled at only one light level. If the resistance at other light levels is a concern,

please contact the factory.

To obtain the typical resistance versus illumination characteristic

for a specif ic part nu m ber:

1. Look up 2 footcandle resistance in table.

2. Insert r esist ance given and draw a curve thr ough th at poi nt

an d parallel to the closest m ember of the fami ly of curv es

shown for the appropriate type of photo-sensitive material.

Resist ance vs. Illum ination

Response Time vs. Illuminat ion

(Ri se Tim e) Response Time vs. Illuminat ion

(Decay Time)

Photoconductive Cell Typical Characteristic Curves

@ 25°C Type Ø Material

Rel ative S p ectral Response

Relative Resistance vs. Temperature

Photoconductive Cell Typical Characteristic Curves

@ 25°C Type 3 Material

Type 3 Material

Th is i s a high speed m ateria l w i th a spect ral r e sponse cl o sel y approxi m at ing t he huma n eye. T hi s m at e rial i s well su it e d fo r switching

from o ne light level t o another and of fe rs our b est tem per atur e s tabi l it y and r e sponse t i m e. Thi s materi al i s oft en used i n ca mera s and

indu st ri al controls.

The resistance for any standard catalog cell is controlled at only one light level. If the resistance at other light levels is a concern,

please contact the factory.

To obtain the typical resistance versus illumination characteristic

for a specif ic part nu m ber:

1. Look up 2 footcandle resistance in table.

2. Insert r esist ance given and draw a curve thr ough th at poi nt

an d parallel to the closest m ember of the fami ly of curv es

shown for the appropriate type of photo-sensitive material.

Resist ance vs. Illum ination

Response Time vs. Illuminat ion

(Ri se Tim e) Response Time vs. Illuminat ion

(Decay Time)

Photoconductive Cell Typical Characteristic Curves

@ 25°C Type 3 Material

Rel ative S p ectral Response

Relative Resistance vs. Temperature

Photoconductive Cell Testing and General Notes

Production Te stin g of Photoce ll s - Pe rkinElme r’s New App roach

Historically within this industry, vendors have set their

production testers to the limits specified on the

customer’s print. Measurement errors due to ambient

temperature, calibration of light source, light history

e ffect, plus an y tester errors have al way s guaranteed that

a certain percentage of the cells shipped are out of

specification.

This practice is incompatible with the realities of today’s

mar ketp lac e, wh er e qual i ty level s ar e bein g mea su red in

parts per million.

With this new catalog, PerkinElmer is taking the

opportunity to correct this situation. for parts in this

catalog, PerkinElmer has pulled in the test limits on our

production testers to compensate for measurement

errors.

General Notes

(Refer to the following data specification pages.)

Ph otocel l s a r e supp l i ed categorize d i nt o gr ou ps by resi st an ce. All gr oups mu st be purc ha sed t o get he r and Per k i nEl m er m ai ntai ns

the righ t to determine the product m i x among t hese groups .

Di m ensi o n cont rol l e d at ba se of packa ge.

Photocells are tested at either 1 fc or 10 lux. 2 fc typical values shown in the tables are for reference only.

Ce lls are light a dapted at 30 - 50 fc .

Th e ph otocel l “gr id” patter n can va ry f rom that s hown. Perk inEl m er reserves t he ri ght to change mix gr id pat terns on any st a ndard

product.

The re sis ta nce for any s tan dard ce ll is co ntr oll ed at onl y o ne l ig ht l evel. If the res ist an ce at o th er ligh t levels is a co ncer n, p lea se

contact the factory.

Photoconductive Cell VT9 00 Ser ies

PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation

Derate Above 25° C PD

∆PD / ∆T80

1.6 mW

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

ELECTRO-OPTICAL CHARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Res i stance (O hms)

Material

Type

Sensitivity

(γ, ty p.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, typ.)

10 lux

2850 K 2 fc

2850 K Dark

Min. Ty p. Max. Typ. Min . sec. Ri se (1 -1/e) Fall (1/ e )

VT9ØN1 6 k 12 k 18 k 6 k 200 k 5 Ø 0.80 100 78 8

VT9ØN2 12 k 24 k 36 k 12 k 500 k 5 Ø 0.80 100 78 8

VT9ØN3 25 k 50 k 75 k 25 k 1 M 5 Ø 0.85 100 78 8

VT9ØN4 50 k 100 k 150 k 50 k 2 M 5 Ø 0.90 100 78 8

VT93N1 12 k 24 k 36 k 12 k 300 k 5 3 0.90 100 35 5

VT93N2 24 k 48 k 72 k 24 k 500 k 5 3 0.90 100 35 5

VT93N3 50 k 100 k 150 k 50 k 500 k 5 3 0.90 100 35 5

VT93N4 100 k 200 k 300 k 100 k 500 k 5 3 0.90 100 35 5

VT935G

Group A 10 k 18.5 k 27 k 9.3 k 1 M 5 3 0.90 100 35 5

Group B 20 k 29 k 38 k 15 k 1 M 5 3 0. 90 100 35 5

Group C 31 k 40.5 k 50 k 20 k 1 M 5 3 0.90 100 35 5

3 6

LOG (R10/R 100)

LOG (100/10)

-------------------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Photoconductive Cell VT 800 Ser ies

PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation

Derate Above 25° C PD

∆PD / ∆T175

3.5 mW

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

EL ECTRO- OPTIC AL CH ARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Resistance (Ohms)

Material

Type

Sensitivity

(γ, ty p.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, ty p.)

10 lux

2850 K 2 fc

2850 K Dark

Min . Typ. Max. Typ. Min . sec. Ri se (1-1 /e) Fall (1 /e)

VT8ØN1 4 k 8 k 12 k 4 k 100 k 5 Ø 0.80 100 78 8

VT8ØN2 8 k 16 k 24 k 8 k 500 k 5 Ø 0.80 200 78 8

VT83N1 6 k 12 k 18 k 6 k 100 k 5 3 0.95 100 35 5

VT83N2 12 k 28 k 36 k 14 k 500 k 5 3 0.95 200 35 5

VT83N3 24 k 48 k 72 k 24 k 1 M 5 3 0.95 200 35 5

VT83N4 50 k 100 k 150 k 50 k 2 M 5 3 0.95 200 35 5

3 6

O G (R10/R 100)

LOG (100/10)

------------------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Dual Element Photoconductive Cell

VT800CT Series PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation (Per Element)

Derate Above 25° C PD

∆PD / ∆T80

1.6 mW

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

ELECTRO-OPTICAL CHARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Resistance Per Element (Ohms)

Matching

@ 10 Lux

R1–2 / R2–3

Material

Type

Sensitivity

(γ, typ.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, typ.)

10 lux

2850 K 2 fc

2850 K Dark

Min. Typ . Max. Typ. Min. sec. Rise (1-1/e) F all (1/e)

VT83CT 30 k 60 k 90 k 30 k 1 M 5 0.70 – 1.30 3 0.90 100 35 5

3 6

O G (R10/R 100)

LOG (100/10)

------------------------------------

PerkinElmer Optoelectronics, 10 900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

VT 800C T Se ries

Photoconductive Cell VT 400 Ser ies

PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation

Demand (20 minutes)

Derate Above 25° C

∆PD / ∆T

400

600

8.0

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

EL ECTRO- OPTIC AL CH ARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Resistance (Ohms)

Material

Type

Sensitivity

(γ, ty p.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, ty p.)

1 fc

6500 K 2 fc

2850 K Dark

Min . Typ. Max. Typ. Min . sec. Ri se (1-1 /e) Fall (1 /e)

VT43N1 4 k 8 k 12 k — 300 k 30 3 0.90 250 90 18

VT43N2 8 k 16 k 24 k — 300 k 30 3 0.90 250 90 18

VT43N3 16 k 32 k 48 k — 500 k 30 3 0.90 400 90 18

VT43N4 33 k 66 k 100 k — 500 k 30 3 0.90 400 90 18

3 6

O G (R10/R 100)

LOG (100/10)

------------------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Photoconductive Cell VT2 00 Ser ies

PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation

Derate Above 25° C PD

∆PD / ∆T50

1.0 mW

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

ELECTRO-OPTICAL CHARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Res i stance (O hms)

Material

Type

Sensitivity

(γ, ty p.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, typ.)

10 lux

2850 K 2 fc

2850 K Dark

Min. Ty p. Max. Typ. Min . sec. Ri se (1 -1/e) Fall (1/ e )

VT2ØN1 8 k 16 k 24 k 8 k 200 k 5 Ø 0.80 100 78 8

VT2ØN2 16 k 34 k 52 k 17 k 500 k 5 Ø 0.80 100 78 8

VT2ØN3 36 k 72 k 108 k 36 k 1 M 5 Ø 0.80 100 78 8

VT2ØN4 76 k 152 k 230 k 76 k 2 M 5 Ø 0.80 200 78 8

VT23N1 20 k 40 k 60 k 20 k 500 k 5 3 0.85 100 35 5

VT23N2 42 k 86 k 130 k 43 k 1 M 5 3 0. 85 100 35 5

VT23N3 90 k 180 k 270 k 90 k 2 M 5 3 0. 85 100 35 5

3 6

LOG (R10/R 100)

LOG (100/10)

-------------------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Photoconductive Cell VT 300 Ser ies

PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation

Derate Above 25° C PD

∆PD / ∆T125

2.5 mW

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

EL ECTRO- OPTIC AL CH ARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Resistance (Ohms)

Material

Type

Sensitivity

(γ, ty p.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, ty p.)

10 lux

2850 K 2 fc

2850 K Dark

Min . Typ. Max. Typ. Min . sec. Ri se (1-1 /e) Fall (1 /e)

VT3ØN1 6 k 12 k 18 k 6 k 200 k 5 Ø 0.75 100 78 8

VT3ØN2 12 k 24 k 36 k 12 k 500 k 5 Ø 0.80 200 78 8

VT3ØN3 24 k 48 k 72 k 24 k 1 M 5 Ø 0.80 200 78 8

VT3ØN 4 50 k 100 k 150 k 50 k 2 M 5 Ø 0. 80 300 78 8

VT33N1 20 k 40 k 60 k 20 k 500 k 5 3 0.90 100 35 5

VT33N2 40 k 80 k 120 k 40 k 1 M 5 3 0. 90 200 35 5

VT33N3 80 k 160 k 240 k 80 k 2 M 5 3 0.90 200 35 5

3 6

O G (R10/R 100)

LOG (100/10)

------------------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Dual Element Photoconductive Cell

VT300CT Series PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation (Per Element)

Derate Above 25° C PD

∆PD / ∆T50

1.0 mW

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

ELECTRO-OPTICAL CHARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Resistance Per Element (Ohms)

Matching

10 Lux

R1–2 / R2–3

Material

Type

Sensitivity

(γ, typ.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, typ.)

10 lux

2850 K 2 fc

2850 K Dark

Min. Typ . Max. Typ. Min. sec. Rise (1-1/e) F all (1/e)

VT3ØCT 10 k 20 k 30 k 10 k 500 k 5 0. 70 – 1.30 Ø 0.80 200 78 8

VT33CT 60 k 120 k 180 k 60 k 1 M 5 0.70 – 1.30 3 0.90 200 35 5

3 6

O G (R10/R 100)

LOG (100/10)

------------------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

VT300CT Series

Photoconductive Cell VT 500 Ser ies

PACKAGE DIMENSIONS inch (mm)

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Rating Units

Continuous P ower Dissipation

Derate Above 25° C PD

∆PD / ∆T500

10 mW

mW/°C

Temperature Range

Operating and Storage TA–40 to +75 °C

EL ECTRO- OPTIC AL CH ARACTERICTICS @ 25°C (16 hrs. light adapt, min.)

See page 13 for notes.

Part

Number

Resistance (Ohms)

Material

Type

Sensitivity

(γ, ty p.)

Maximum

Voltage

(V, pk)

Response Time @ 1 fc

(ms, ty p.)

10 lux

2850 K 2 fc

2850 K Dark

Min . Typ. Max. Typ. Min . sec. Ri se (1-1 /e) Fall (1 /e)

VT5ØN1 4 k 8 k 12 k 4 k 200 k 5 Ø 0.75 200 78 8

VT5ØN2 8 k 16 k 24 k 8 k 500 k 5 Ø 0.75 200 78 8

VT5ØN3 16 k 32 k 48 k 16 k 1 M 5 Ø 0.80 300 78 8

VT53N1 16 k 32 k 48 k 16 k 1 M 5 3 0.85 200 35 5

VT53N2 32 k 76 k 96 k 38 k 2 M 5 3 0.85 200 35 5

VT53N3 66 k 132 k 200 k 66 k 3 M 5 3 0.85 300 35 5

3 6

O G (R10/R 100)

LOG (100/10)

------------------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Application Notes—Photoconductive Cells

APPL IC ATION N OTE #1

Light - Some Physical Basics

Light is pr oduced by the rele ase of ener gy from the atoms of a material

when they are excit ed by heat, chemica l reaction or other means . Light

travels through space in the form of an electromagnetic wave.

A consequence of this wave-like nature is that each “color” can be

completely defined by specifying its unique wavelength. The

wavelength is defined as the distance a wave travels in one cycle.

Since the wavelengths of light are very short they are normally

measured in nanometers, one nanometer being equal to 1 x 10

-9

meters.

The spect ral response of Per kinElmer’s photoconductor s are specified

by lots of relative response versus wavelength (color) for various

ma te r ia l ty p es.

N a t ur a l Il lu min a nc e R o o m Il lu min a t ion

Ultraviolet

(To X-rays and Gamm a Rays) Infrared

(To Radar W aves )

Visible Light

400 700

Violet Red Wavelength

Violet Below 450 nm

Blue 450 - 500 nm

Green 500 - 570 nm

Yellow 570 - 590 nm

Orange 590 - 610 nm

Red 610 - 700 nm

Sky Condition Light Level (Typical)

Direct Sunlight 10000 fc

Overcast Day 1000 fc

Twilight 1 fc

Full Moon 0.1 fc

Clear Night Sky (m oonless ) 0.001 fc

Lighting Condition Light Level (Typical)

Candle - Lit Room 5 fc

Auditorium 10 fc

Classroom 30 fc

Inspection Station 250 fc

Hospital Operating Room 500 - 1000 fc

Application Notes—Photoconductive Cells

APPL IC ATION N OTE #2

Light Resistance Measurement Techniques

The l ight resistance or “on” resistance (RON) of a photoconductor cell

is defined as the resistance of the cell as measured at a special light

level using a light source with a known output spectrum. Fur thermore,

the cell must be “light adapted” for a specific period of time at an

es tablished level of ill um ination in or der to achieve repe atable results.

The industry standard light source used for light resistance

measurements is a tungsten filament lamp operating at a color

temperature of 2850 K. Specifyi ng the 2850 K col or tempera ture f or the

lig ht source fi x es the spectr al output (i.e . the tungs ten f ilament light has

fixed amounts of blue, gr een, red, and infra re d light).

For consistency and ease of comparing different cells, PerkinElmer

lists light resistance values for its photocells at two standard light

levels: 2 fc (footcandles) and at 10 lux. The footcandle is the old,

historical unit for measuring light intensity and is defined as the

illumination produced when the light from one standard candle falls

no rmally on a surf ace at a dist ance of one foot. The lux (the m etric unit

of light measurement) is the illumination produced when the light from

one candle falls normally on a surface of one meter. The conversion

be tween footca ndle and lux. i s as follo ws:

1.0 fc = 10.76 lux

1.0 lux = 0. 093 fc

As explained in the section on “Selecting a Photocell”, the “light

history” effect necessitates the pre-conditioning of the cell before a

light resistance measurement is made. PerkinElmer stores all cells at

room tempe r ature f or 16 hours minimum at 3 0 – 50 fc (abou t 320 - 540

lux) prior to makin g the test measurement.

Sometimes the design engineer or user does not have access to the

precision measurement equipment necessary to determine the light

levels or light intensities of the application. Should this prove to be a

problem, calibrated photocell samples with individual data can be

provided by P erki nElmer.

APPL IC ATION N OTE #3

Spectr al Output of C omm on Light Sources

Incandescent lamps can be considered as black body radiator s whose

spectral output is dependent on their color temperature. The sun has

ap pr oximately the same sp ect ral r adiatio n distribution as tha t of a black

body @ 5900 K. However, as viewed fr om the surface of the earth, the

su n's spe c trum cont ains H

O and C O

abso rption bands .

Black Body Sources Output vs. Wavelength

Fluorescent lamps exhibit a broad band spectral output with narrow

peaks in certain parts of the spectrum. Shown below is a plot of the

light output of a typical daylight type fluorescent tube.

Fluorescent Lamp Output vs. Wavelength

Due to their long operating lifetimes, small size, low power

consumption, and the fact they generate little heat, LEDs are the light

sources of choice in many applications. When biased in the forward

dir ection LE Ds emit l ight tha t is very nar r ow in spectral bandwi dth (l ight

of one color). The “color” of the light emitted depends on which

semiconductor material was used for the LED.

Application Notes—Photoconductive Cells

LED Light Sour ces

APPL IC ATION N OTE #4

Spectral Matching of LEDs and

Photoconductive Types

Since light sources and light detectors are almost always used

together t he designer must take i nto consideration the optical coupling

of th is syst em or the abi lity of the det ector to “see” the light source.

In order to have good optical coupling between the emitter and the

co nduct or the spectral o ut put of the li ght source m ust , t o some degree,

o verlap the spectral response of t he detector. If the d esign involves the

use of a light source with a broad band spectral output the designer is

assured that the photocell will have good response to the light. This

ma y not be t he case when an LED light source is employed. LED s emit

their light within a very narrow spectral band so that they are often

considered to be emitting at only on (peak) wavelength.

Spectral matching factors were calculated for a number of different

LEDs and the photoconductor material types manufactured by

PerkinElmer. Each matching factor was derived by multiplying the

detector response curves by the LED spectral output curve and then

mea s uring the resul ti ng area.

The LED/photocell matching factors listed are independent of power

out put from the LEDs. In order to get a real feel on how well any LED/

photocell pair couple together, the power output from the LED at a

pa rticular forward drive cu rrent must be consi der ed.

Normalized LED/Photocell Matching

The int ensity of the light bein g em it ted by visib le LEDs is often given in

units of millicandela. Millicandela is phot ometric unit of measure which

as sum es the human ey e as the detector. For most detector s other th an

the human eye the most convenient system for measurement is the

radiometric system. Listed below is the typical light power output of

so me LED s m easured at tw o diff er ent forward driv e cur rents. N ote that

LEDs of a given type can show a 5:1 manufacturing spread in power

outputs.

LED Type Color λP

GaP GREEN 569 nm

GaAsP/GaP YELLOW 585 nm

GaAsP/GaP ORANGE 635 nm

GaAsP/GaAs RED 655 nm

AIGaAs RED 660 nm

GaP/GaP RED 697 nm

GaAIAs INFRARED 880 nm

GaAs INFRARED 940 nm

LED Type λP (nm) Type Ø Material Type 3 Mater ial

GaP 569 39% 40%

GaAsP/GaP 58 60% 52%

GaAsP/GaP 635 49% 38%

GaAsP/GaAs 655 31% 27%

AIGaAs 66 31% 27%

GaP/GaP 697 47% 31%

GaAIAs 880 — —

GaAs 940 — —

LED Type Color λP (nm) Power Output

If = 1 mA If = 10 mA

GaP GREEN 569 nm 1.2 µW 24.1 µW

GaAsP/GaP YELLOW 585 nm 0.3 µW 26.2 µW

GaAsP/GaP ORANGE 635 nm 3.2 µW 101.9 µW

GaAsP/GaAs RED 655 nm 6.2 µW 102.1 µW

AIGaAs RED 660 nm 33.8 µW 445.1 µW

GaP/GaP RED 697 nm 54.3 µW 296.2 µW

GaAIAs INFRARED 880 nm 76.8 µW 1512.3 µW

GaAs INFRARED 940 nm 35.5 µW 675.0 µW

Application Notes—Photoconductive Cells

Factoring in the power outputs of the LEDs, in this case at a forward

drive current of 10 ma, coupling factors (matching factor multiplied by

power output) for the various LED/material type combinations can be

generated.

Normalized LE D/Photocell Coupling Factors @ 10 mA

Once gain, this data is intended as a general guide. LED power

out puts can var y 5:1 between manufacturer lots.

APPL IC ATION N OTE #5

Assembly Precautions

When soldering the cell leads take all measures possible to limit the

amount of heating to the photocell. The maximum recommended

soldering temperature is 250°C with a solder duration of 5 seconds.

Heat sink the LEDs if possible. Keep soldering iron 1/16 inch (1.6 mm)

minimum from base of package when solder ing.

Avoid chemicals which can cause metal corrosion. Do not clean the

plastic coated cells with organic solvents (ketone types). Check with

factory for specific cleani ng r ecom m endations.

Finally refrain from storing the cells under high temperature and/or

humidity conditions. If cells are stored in the dark for any length of time

please “lig ht adept” before test ing (see sect ion on Light Hi sto ry Effect).

Storage in the dark will change both the sensitivity and decay time of

the cell.

APPL IC ATION N OTE #6

A Low Cost Light Source for Measuring

Photocells

he Light Source used in the measurement of photocell resistance

must be characterized for intensity and spectral composition.

PerkinElmer uses a tungsten filament lamp having a spectral output

approximating a black body @ 2850 K with a known candlepower

ou tp ut at a s pecifi ed voltage and curr ent.

While calibrated lamps of this type are available from the National

Institute of Standards and Technology (formerly NBS) and private

testing labs, a low cost alternative is to use a 100 W, inside frosted,

tungsten filament lamp available from any home or hardware store.

Such a lamp operated at 120 VAC will produce approximately 90

candlepower (cp) of illumination and a color temperature of 2700 K to

28 00 K.

The relationship betw een candl epower and f ootc andle is:

Since this equation assumes a point source of light, the distance

between lamp and detector should be at least five times the lamp

diameter.

There are some characteristics of incandescent lamps which should

be noted:

1. Color temperature increases wit h increasing wattage.

2. Wh en oper ated at a constant curr ent , light output rises wi th time.

LED Type λP (nm) T ype Ø Type 3

GaP 569 3% 3%

GaAsP/GaP 58 5% 5%

GaAsP/GaP 635 17% 13%

GaAsP/GaAs 655 11% 9%

AIGaAs 66 47% 35%

GaP/GaP 697 47% 31%

GaAIAs 880 — —

GaAs 940 — —

footcandle candle power

distance in feet()

----------------------------------------=

Application Notes—Photoconductive Cells

APPL IC ATION N OTE #7

How to Specify a Low Cost Photocell

Sometimes the dem ands of the application such as power dissipation,

“on” resistance, voltage, temperat ur e coefficient, etc. limit the selection

of the photocell to one particular device. Ho wever, more common is the

case where any number of photocell types can be used, especially if

minor changes are undertaken at an early enough point in the circuit

de sign. In these cases, price is often the deciding f actor.

Many factors influence price. In order to give some guidance and

weight to these factors the reader is referred to the following table

which is meant to serve as a general guid e.

Lower Cost Factor Higher Cost

Plastic Packaging Glass/Metal

Broad Resistance Range Narrow

Small Package Size Large

Open Order with

Scheduled Releases Scheduling Released Order s

Standard Tests Testing Special Tests

Analog Optical Isolators VACTROLS®

What Are Analog Optical Isolators?

PerkinElmer Optoelectronics has been a leading manufacturer of

an alog opti cal isolators for o ver twenty years and m akes a b ro ad r ange

of sta ndard parts under it s tr ademark VACTRO L®.

There are many kinds of optical isolators, but the most common is the

LED/phototransistor type. Other familiar types use output elements

such as light sensitive SCRs, Triacs, FETs, and ICs. The major

application for these silicon based devices is to provide electrical

isolation of digital lines connected between different pieces of

equipment. The principle of operation is very simple. When an input

cur rent is applied to the LE D, the output phototransistor turns on. The

only connection between the LED and phototransistor is through

light—not electricity, thus the term optical isolator. These optical

isolator s ar e pr imarily digit al in nature wit h fast response times suita ble

for interfacing with logic gates. Rise and fall times of a few

mi cr oseconds, faster f or som e isol ators, ar e typi cal.

The analog optical isolator (AOI) also uses an optical link between

input and output. The input element is an LED and the out put element

is always photoconductive cell or simply photocell. Together, the

coupled pair act as an electrically variable potentiometer. since the

output element of the AOI is a resistor, the voltage applied to this

output resistor may be DC and/or AC and the magnitude may be as

low as zero or as high as the maximum voltage rating. Because the

input will control the magnitude of a complex waveform in a

proportional manner, this type of isolator is an analog co ntr o l e lem ent.

AO Is may be used in the ON-OFF mode but the fastest response time

is only in the millisecond range. A level sensitive Schmitt trigger is

required between the AOI and logic gates when used in digital circuits.

The figur e below sho ws the ci rcuit diagram of a stan dard AOI.

AOI Circuit Dia gram

In put Element

Light emitting diodes used in AOIs are usually visible LEDs best

matching the sensitivity spectrum of the photocell output element.

LEDs are the ideal input element in most applications. They require

low drive current and voltage, respond very fast and have virtually

unlimited life. They are ver y rugged and are unaffected by shock and

vibration. Since the LED is a diode, it conducts in one direction only.

They must be prot ected from excessive forward current due to the low

dynamic resistance in the forward direction. The forward character istic

of an LED ty pically used in VACTROLs i s shown below.

LED Forw ard Characteristics

Output Element

The output element in all PerkinElmer’s AOIs is a light dependent

resistor (LDR), also called a photoconductor or photocell. Photocells

are t rue resistors.

These passive resistors are made from a light sensitive polycrystalline

semiconductor thin film which has a very high electron/photon gain.

There are no P/N junctions in a pho tocell, maki ng it a bilateral device.

The resistance of the photocell depends on the amount of light falling

on the cell. For a given illumination, the amount of electrical current

through the cell depends on the vol tage applied. This voltage may be

either AC or DC. Thus, the photocell is the ideal low distortion output

elem ent for an analog optoisolat or.

A complete discussion of photoconductive cells can be found in the

first section of this book.

What Are Analog Optical Isolators?

Light History Considerations

Phot oconduct iv e cells ex hibi t a phenome non kno ws as hyst eresis , light

memor y, or light histor y effect. Special consideration must be given to

this characteristic in the analog optoisolator because the

photoconductive element is normally in the dark. This will lead to

having the photocell initially in a “dark adapted” state in many

conditions.

The light levels that are seen by the photocell in many analog

opt oisolator applications are quite low, ranging from 0.1 to 1.0 fc. The

effect of thi s com bination of dark adapt and low l ight le vels will be seen

in the fo llowi n g t able.

The table shows the relationship between light history and light

resi stance at vario us light level s for different m aterial types. The values

shown were determined by dividing the resistance of a given cell,

following “infinite” light history (R

), b y the resistance of the same cell

following infinite dar k history (R

). For pr actical pu rposes , 24 hours i n

the dar k will achi ev e R

or 24 at appro ximately 30 fc wi ll achie ve R

Variation of Resistance with Light History Expressed as a

Ratio R

at Various Test Illumination Levels

The table illustrates the fact that the resistance of a photocell can

incr ease subst antial ly as it transit ions from dark adapted sta te to a light

adapted state. The table shows that the Type 1 photocell can incr ease

resistance by a factor of more than three times as it light adapts up to

0.1 fc. In some applications, this can be an important consideration. In

general, the magnitude of this effect is larger for types 1, 4, and 7 than

for types Ø, 2, and 3.

Each specific material type represents a tradeoff between several

characteristics. Selecting the best m ater ial is a pr ocess of determining

what characteristics are most important in the application. The chart

gives some appreciation for the general interrelationships bet ween the

material types and their propert ies.

Material

Type

Illum ination (fc)

0.01 0.1 1.0 10 100

Type Ø 1.60 1.40 1.20 1.10 1.10

Type 1 5.50 3.10 1.50 1.1 0 1.05

Type 2 1.50 1.30 1.20 1.1 0 1.10

Type 3 1.50 1.30 1.20 1.1 0 1.10

Type 4 4.50 3.00 1.70 1.1 0 1.10

Type 7 1.87 1.50 1.25 1.1 5 1.08

What Are Analog Optical Isolators?

Re lative R esistance vs. Temperat ure

Type Ø Material

Re lative R esistance vs. Temperat ure

Ty pe 1 Material

Relative Resistance vs. Temperature

Ty pe 2 Material

Relative Resistance vs. Temperature

Ty pe 3 Material

Material Characteristics

(General Trends)

Types 2 & 3 Type Ø Type 7 Type 4 Type 1

Lower Temperature Coefficient Higher

Higher Sheet Resis tivity Lower

Slower Speed of Response Faster

Lower Resistance Slope Higher

Smaller Light History Effect Larger

What Are Analog Optical Isolators?

Relative Resist ance vs. Tempe rature

Type 4 Material

Relative Resist ance vs. Tempe rature

Type 7 Material

Typical Applications of Analog Optical Isolators

Why Use Analog Optical Isolators?

Per kin El mer O pt oelec tr oni cs’ li ne o f an alog op tic al i sol ato rs (AO Is ) con sis ts o f a lig ht tigh t p ackage whi ch h ous es a lig ht source and

one or more photoconductive cells. Through control of the input current or voltage applied to the AOI, the output resistance can be

varied. The output resistance can be made to switch between an “on” and “off ” state or made to track the input signal in an analog

manner. Because a small cha nge in input sign al can cau se a larg e c hange in ou tput resist ance, AOIs have be en found to prov ide a

very economic and technically superior solution for many applications. Their general characteristics and salient features can be

summarized as follows:

• H ig h input-t o-output voltage isol at ion

• True r esistance el ement output

• S in gle or dual element outputs ava ilable

• Low cost

• S ui t able for AC or DC use

• Wi de rang e of input to outpu t characteristi cs

• Low driv e current

• Low “on” resistance, high “off” resistance

• Comple te solid -state constr u ction

Applications

Analog Optical Iso lators are u sed in many different types of cir cuits and appl ications. H ere is a list of on ly a few ex amples of w here

A OIs have been used.

• DC isolators

• Feedback elements in automatic gain control circuits

• A udio limiting and compression

• Noiseless s witching

• Logic interf a cing

• Remote gain control for amplifiers

• Photochoppers

• Noiseless potentiometers

Typical Applications of Analog Optical Isolators

Typi ca l Appl ic ation C ircu it s

Automatic Gain Co n trol (AGC)

Remote Gain Control

Nois ele ss Switc hing/Logic Interfaci ng

(See Application Note #1)

Audio Applications

Characteristics of Analog Optical Isolators

Transfer Characteristics

The light output of an LED is proportional to the input drive current, I

Some LEDs will begin to radiate useful amounts of light output at

forward currents as low as 10 µA. These same LEDs can be dr iven at

50 mA with no degradation in perfor m ance.

A transfer curve of output resistance versus input light current for a

typical AOI is shown in Figure 1. AOIs not only possess a large

dynamic range, but the output resistance tracks the input current in a

somewhat linear manner over a range of two or more decades.

This characteristic makes the AOI suitable for use in a very broad

range of applications, especially in audio circuits where they are used

for switching, limiting, and gating. For a more ext ensive discussion on

AO Is in audio circuits, refer to Application Notes #1.

Resp ons e Tim e

AOIs are not high speed devices. Speed is limited by the response

time of the photocell. With rise and fall times on the order of 2.5 to

15 00 ms ec, most AOIs ha ve bandwidt hs bet ween 1 Hz and 200 Hz.

Figure 1. T ransfer Curves (25°C)

One of the characteristics of photocells is that their speed of response

incr eases with increasing levels of il luminatio n

Thus the bandwidth o f

Vactrols is somewhat dependent upon the input drive level to t he LED.

In general , th e higher the input drive the wider the ban dwi dth.

The turn-off time and turn-on time of photocells are not symmetrical.

The turn-on time can be an order of magnitude faster than the tur n-off

time. In the dark (no input), the resistance of the cell is very high,

typically on the order of several megohms. When light is suddenly

applied, the photocells resistance drops very fast, typically reaching

63 % (1-1/ e conductance) of its final v alues in under 10 msec.

When the light is removed, the resistance increases initially at an

exponential rate, approximately tripling in a few milliseconds. The

resi stance then i ncr eases linearly wi th time .

The fast turn-on and slow turn-off characteristics can be used to

advantage in many applications. This is especially true in audio

applications where a fast t urn-on (attack) and a slow turn-off (release)

is preferred. For example, the typical AOI can be made to turn-on in

100 to 1000 µsec. In a limited circuit this is fast enough to catch high

pe ak amplitudes but no t so fast as to cause ob vious clippi ng. The turn-

off wi ll take as muc h as 100 times longer so the audio circuit w il l r eturn

to a normal gain conditi on without a disturbing “thump” in the speaker.

Figure 2. Resistance vs. Time

Noise

The sources of electrical noise in the output element of AOIs are the

sam e as for any other type of resistor.

One source of noise is thermal noise, also known as Johnson or

“white” noise, which is caused by the random motion of free electrons

in the photoconduct ive material .

1. For a more co mprehensive discussion on the turn-on and turn-

off characteristics of photocells and how r esponse time i s effect-

ed by light level , see the Photoconductive Cell s ection of this cat-

alog.

Characteristics of Analog Optical Isolators

Some major characterist ics of Johnson no ise are that it is:

1. Independ ent of frequency and contains a const ant power density

pe r un it of bandwidth.

2. Temperature de pendent, increasing with incr eased temperature.

3. Dependent on photocell re sist ance value.

Jo hnson n oise is defined by t he followi ng equation:

where:

= J ohnson noise current, amps RMS

k = Bolt zmann’ s constant, 1.38 x 10

-23

T = temperature, degrees Kelvin

R = phot ocell resistance

BW = bandwidt h of interes t, Hertz

A second type of noise is “shot” noise. When a direct current flows

through a device, these are some random variations superimposed on

this current due to r andom fluct uations i n the em ission of elect rons due

to photon absorption. The velocity of the electrons and their transit

time wil l also have an effect.

“S hot” noise is :

1. Independent of frequency.

2. Dependent upon the direct current flowing through the phot ocell.

Shot noise is defined by the following equa ti on:

where:

= sho t noi se cur rent, amps RMS

e = elect r on char ge, 1.6 x 10

-19

= dc curr ent , amp s

BW = bandwidt h of interes t, Hertz

The third type of noise is flicker of 1/f noise. The sour ce of 1/f noise is

not well understood but seems to be attributable to manufacturing

noise mech anisms. It s equation is as follows:

where:

= f licker n oise, amps

K = a const ant that depends on the type of mat erial

and its geometr y

= dc curr ent , amp s

BW = bandwidth of interest, Hertz

f = frequency, Hertz

Unlike ther mal or shortnoise, flicker noi se has 1/f spectral densi ty and

in the ideal case for which it is exactly proportional to , it is

termed “pink noise”. Unfortunately, the constant (K) can only be

determined empirically and may vary greatly even for similar devices.

Flicker noise may dominate when the bandwidth of interest contains

fr equencies less t han about 1 kHz.

In most AOI circuits noise is usually so low that it is hardly ever

considered. One notable exception is in applications where large

voltages are placed across the cell. For a typical isolator, it takes 80 to

100V across the photocell before the noise level starts to increase

significantly.

Distortion

Analog Optical Isolators have found wide use as control elements in

au dio cir cuits because they possess two cha r acteristics which no other

active semiconductor device has: resi stance output and low harmonic

distortion. AOIs often exhibit distortion levels below -80 db when the

v oltage applied to the photocell output is kept belo w 0.5V.

Figure 3 shows the typical distortion generated in typical AOIs. The

distortion depends on the operating resistance level as well as the

applied vol tage. The minimum distor tion or threshold distortion shown

in Figure 3 is a second harmonic of the fundamental frequency. The

actual source of this distortion is unknown, but may be due to some

type of crossover nonlinearity at the original of the I-V curve of the

photocell.

INJ 4kTBW()R⁄=

INS 2eIdcBW=

INF KIdcBW f⁄=

1f⁄

Characteristics of Analog Optical Isolators

Figure 3. Typical LED AOI Distortion Characteristics

At high AC voltages, distor tion to the waveform can be seen using an

oscilloscope. The waveform is still symmetrical but contains the

fundamental and the odd harmonics, the third harmonic being

predominant. If there is DC as well as AC voltage on the photocell,

bot h even and odd harm onics are generated.

The RMS value of voltage or current is not very sensitive to a large

third harmonic component, but the instantaneous value is. A 10%

harmonic will only change the RMS values by 0.5%. If the output is

used to control a thermal element, such as a thermal relay, circuit

operation is not affected. Further, when the AOI is used in ON-OFF

ap pli cations, waveform dist ortion is not a pro blem.

(a) (b)

(d)(c)

Characteristics of Analog Optical Isolators

Vo ltage Rat ing

The maximum voltage rating of the output element (photocell) applies

only when the input is off. Two different kinds of dark current “leakage”

characteristics are observed in photocell output elements. Figure 4

shows the soft breakdown found in lower resistivity materials. Wit h no

input, if the appl ied voltage is suddenly increased from zero to V

, the

current increases along section ‘a’, with the steepness depending on

the rate at which the voltage is increased. If the voltage is now held at

V1, the current decreases along curve ‘b’ and stabilizes at a much

lower value. If the voltage is again increased, the next section of the

curve is traversed with the current dropping along curve ‘d’ in time.

This process can be repeated until the reverse current becomes so

great that the cell bur ns up. The maximum voltage rating for phot ocells

with this soft reverse characteristic is based on a safe steady-state

po w er dissipati on in the OFF condition.

Figure 4. Breakdown ch aracteristics of photocells with low resistivity

photocon ductive material.

Higher resistivity photoconductive materials do not show the reverse

characteristics of Figure 4 to any significant degree. As voltage is

increased, the dark current increases, but remains very low until

breakdown occurs. The current then increases in an av alanche fashion

resulting in an arc-over which causes the cell to be permanently

damaged (shorted). The dielectric breakdown voltage is approximately

8 - 10 kV per cm of contact spacing for materials with this type of

reverse characteristic. Photocells have 0.16 - 0.5 mm electrode

sp acing so the maximum v oltage r at ings typically fall int o the 100 - 300

vo lt range.

The high voltage capability of photocells suggests their use as the

se ries pass element in a high v oltage regulated power sup ply. Voltages

up to 5 o r 10 kV can be regulat ed but the current should be lim it ed to 1

or 2 mA. The isolated input element gr eatly simplif ies the circuit design

and the single output element avoids the need for voltage and current

sh aring com ponents.

Power Rating

Photocells are primarily used for signal control since the maximum

allowable power dissipation is low. Typically, the steady-state output

cur rent should be kept below 10 mA on catalog LE D AO Is because of

the small size ceramic used in the output cell. However, the surface

area is large compared to si m il arly rated transist or s, so AOIs withstand

signifi cant transient current and power surges .

Power ratings are given in the catalog and are typically a few hundred

milliwatts, but special AOIs have been made with power dissipation

rat ings as high as 2. 0 W.

Life an d Aging

Life expectancy of an AOI is influenced both by the input and output

devices. Isolators which use an LED have long life si nce LED lifetimes

are long: 10,000 to 200,000 hours, depending on the applicat ion. LED s

no rmally show a decreas e in l ight output for a spe c ified bias current as

they age.

The photocell output elements in AOIs show an increase in output

resi stance over time as they age. Wit h a continuous i nput driv e cu rrent

and with voltage bias applied to the output, the output resistance will

generally increase at a rate of 10 percent per year. The aging rate is

lower with intermittent operation. Figure 5 shows the trend line for

out put resistance under typical operating conditions. Other AOIs using

different photo conductive materials show similar trends.

Figure 5. VTL5C3 Life Test.

Characteristics of Analog Optical Isolators

Storage Cha racteris t ics

The instantaneous output resistance of any AOI is somewhat

dependent on the short term light history of the photocell output

elem ent. Wi th no applied input cur r ent or volt age, the output element is

in the dark. Dark storage causes the cell to “dark adapt”, a condition

which results in an increase in the photocell’s sensitivity to light. When

first turned on, an AOI which has experienced a period of dark

ad apt ion wil l exhibit a lo we r value for “o n” r esistance, at any given drive

condition, than the sam e device which has been continuously on.

The output resistance of an AOI which has been biased “on” is

considered to be constant with time (neglecting long term aging

effects). After the removal of the input drive, the photocell begins to

experience dark adaption. The cell’s rate of increase in sensitivity is

initially high but eventually levels off with time in an exponential

manner. Most of the dark adapt occurs in the first eight hour s, but with

some AOIs for sensitivity can continue to increase for several weeks.

When an AOI which has been sitting in the dark i s turned on, the cell

immediately begins returning to its light adapted state. For any given

device, the rate of recover y is dependent on the input light level.

The type of photoconductive material is the major factor determining

the magnitude of these changes. Lower resistivity materials show

g r eater initi al and final changes but their rate of change is f aster .

These light/dark history effects are pronounced at both high and low

input levels. However, at high input levels, the photocell light adapts

qu it e r apidly, usually in minutes.

Figure 1 shows the transfer curves for an AOI after 24 hour storage

wit h no input and then afte r it has been operated wi th rated input for 24

hours. Because of these “memory” phenomena, it is best to use these

par ts in a closed loop circuit to minimize t he effects of these changes.

Open loop proportional operation is possible if the application can

tolerate variations. The use of the VTL5C2 and VTL5C3 with their

more stable char acteristics wil l hel p.

Temperatur e Range

Operating and stora ge temperature r ange is lim ited at the low er end by

the reduction of dark resistance of the cell and at the upper end by

rapid aging. A t low temperatures, the response time of the output cell

increases. The temperature at which this becomes pronounced

depends on the photoconductive material type. Isolators using low

resistivity materials, as in the VTL5C4, will show this lengthening of

resp onse time at -25°C. Hi gher resist ivity material s such as use d in the

VTL5C3 and VT L5C 6 do not slow down excessiv ely until te mp eratures

get below -40°C. This characteristic is completely reversible with the

response time recovering w hen t he temperat ure ris es.

Storage a t l ow temper ature has no operating effect on AO Is. Unit s m ay

be stored at temperatures as low as -40°C. Lower temperatures may

cause mechanical stress damage in the package which can cause

pe rmanent changes in the AOI transfer charact eri sti cs.

The chemistry of the photoconductive materials dictates a maximum

operating and storage temperature of 75°C. It should be noted that

operation of the photocell above 75°C does not usually lead to

cat astrophi c failur e but the photoconductive surface may be damaged,

leading to irr eversible changes in sensitivity.

The amount of resistance change is a function of time as well as

temperature. While changes of several hundred percent will occur in a

matter of a few minutes at 150°C, it will t ake years at 50°C to produce

that m uch change.

In most applications, operation is intermittent. At elevated

temperatures, the resistance of the cell ri ses during the turn-on period

and recovers during the turn-off period, usually resulting in little net

change. However, if the AOI is stored at elevated temperatures for

many hours with no input signal, there is a net reduction in output

resistance. There w ill be some recovery during operation over time but

it is not possible to predict the rate or to what degree. Elevated

temperatures do not produce sudden cat astrophic failur e, but changes

in t he device transfer curve with time must be anticipated.

Characteristics of Analog Optical Isolators

Capacitance

The equivalent circuit for the output photocell is a resistor in parallel

with the capacitance. The capacitance arises from the topside

metallization of the electrodes which form a coplanar capacitor. The

value of this capacitance is largely determined by the size of the

ceramic base. For lower capacitance, a smaller cell is needed. The

capacitance is so small (3.0 pF, typical on catalog AOIs) that it is

negligible in most applications. However, there are applications such

as wideband or high frequency amplifiers in which the capacitance

needs to be considered. At 4.5 MHz, the video baseband frequency,

the phot ocell capacitive reactance is only 12 kilohms. If the phase shift

of the signal is to be kept below 10°, the highest useful cell resist ance

is only 2.0 kilohms. At high AOI input drive, where the cell is drive

below 1.0 kilohm, the capacitance can increase additionally from 2 to

10 times, possibly due to distr ibuted effects.

Summary

Analog Optical Isolators have many unique features, such as:

1. High input-t o-output isolatio n.

2. True resista nce element output.

3. Wide dynamic range (low “on” resistance/high “off” resi sta nce).

4. Low drive current.

5. Low distort ion.

These features are primarily dependent on which input element and

output element photoconductive material is used in the Vactrol AOI.

Thus, there is a wide variety of Vactrols to choose from for your

application.

Characteristics of Analog Optical Isolators

Typical Transfer Ch aracteri stics (Resistance vs . Input C urrent) For St andard Vactrols

Curves shown are based upon a light adapt condition for 24 hours @ no input at 25°C.

Outp ut Resistance vs. Input Current

VTL5C Series

Outp ut Resistance vs. Input Current

VTL5C Series

Characteristics of Analog Optical Isolators

A nalog Op toisolator Comparis on C hart

Spec ifica tion Not e s

(These notes are referenced on the following LED Vactrol Data Sheet pages.)

Since the input has a substant ially con stant volta ge drop, a current limi ti ng resist ance is r equired.

Da rk adapted resi stance measured aft er 24 or m ore hours of no in put.

Measured 10 sec. after removal of the input. The ultimate resistance is many times greater than the value at 10 seconds.

Ascent measured to 63% of final conductance from the application of 40 mA input. The conductance rise time to a specified value is

increase d at red uced input drive while the c o ndu ct ance de cay tim e to a specif ied value is decreased.

Typical m atchi ng and tracking from 0.4 t o 40 mA is 25%.

Measured 5 sec. after removal of the input. The ultimate resistance is many times greater than the value at 5 seconds.

VT L5C9 re sponse ti mes are based on a 2.0 mA in put. VTL5 C10 response times are based on a 10.0 mA input for as cent tim e and

a 1.0 mA input for decay t i m e.

Device Material Ty pe Slope D ynamic Range Dark Resistance Temperat ure

Coefficient Speed of

Response Light History

Effect

VTL5C1 1 15.0 100 db 50 MΩVery High Very Fast Ver y Large

VTL5C2 Ø 24.0 69 db 1 MΩLow Slow Small

VTL5C2/2 Ø 20.0 65 db 1 MΩLow Slow Small

VTL5C3 3 20.0 75 db 10 MΩVery Low Ve r y Slow Very Small

VTL5C3/2 3 19.0 71 db 1 0 MΩVery Low Ve r y Slow Ver y Small

VTL5C4 4 18.7 72 db 400 MΩHigh Fast Large

VTL5C4/2 4 8.3 68 db 400 MΩHigh Fast Large

VTL5C6 Ø 16.7 88 db 100 MΩLow Slow Small

VTL5C7 7 5.7 75 db 1 MΩAverage Average Average

VTL5C8 Ø 8.0 80 db 10 MΩLow Slow Small

VTL5C9 1 7.3 112 db 50 MΩVery High Very Fast Very Large

VTL5C10 4 3. 8 75 db 400 MΩHigh Fast Large

Low Cost Axial Vactrols VTL5C1, 5C2

PA CKAGE DIMENSIONS inch (mm)

PLASTIC POTTI NG CONTOUR

NOT CONT ROLLED

DESCRIPTION

V TL5C1 offers 100db dy namic range , fast re sponse time , and very hig h dark re sist ance.

VTL5C2 features a very steep slope, low temperature coefficient of resistance, and a small light history memory.

ABSOLUTE MAXIMU M RATIN G S @ 25°C

Maximum Temperatures

Storage and Opera ti ng: –4 0°C to 75°C

Cell Power: 175 mW

Der ate above 30°C: 3.9 m W/°C

LED Current: 40 mA

Der ate above 30°C: 0.9 m A/ °C

LED Reverse Br eakdown Volt age: 3.0 V

LED Forward Voltage Drop @ 20 mA: 2.0V (1.65V Typ.)

Min . Is olation Voltage @ 70% Rel. Humidity: 25 00 VR MS

Out put Cel l C apacitance: 5.0 pF

Cell Voltag e: 10 0V ( VT L5C1),

20 0V (VTL5C2)

Input - Output Cou pli ng Capacit ance: 0.5 pF

ELECTRO-OPTICAL CHARCTERISTICS @ 25°C

Refer to Specification Notes, page 41.

Part

Number Material

Type

ON Resistance OFF

Resistance

@ 10 se c. (Mi n . )

Slope

(Typ.)

Dynamic Range

(Typ.) Response Time

Input current Dark

Adapted

(Typ.)

Tu rn-on to

63% Final RON

(Typ.)

Turn-off (Dec ay)

to 100 kΩ

(Max.)

VTL5C1 1 1 mA

10 mA

40 mA

20 kΩ

600 Ω

200 Ω50 MΩ15 100 db 2.5 ms 35 ms

VTL5C2 0 1 mA

10 mA

40 mA

5.5 kΩ

800 Ω

200 Ω1 MΩ24 69 db 3.5 ms 500 ms

@ 0.5 m A

R@ 5 mA

------------------------ RDARK

R@ 20 mA

------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Typical Performance Curves

Output Resistance vs. Input Current

VTL5C1

Output Resistance vs. Input Current

VTL5C2

Input Charact eristics

Response Time

VTL5C1

Response Time

VTL5C2

Notes:

1. At 1. 0 mA and below, uni ts may ha ve substanti ally higher

resi stance than shown in the typ ical curv es. Consul t factory if

closely controll ed characterist ics are required at low input

currents.

2. Out put resistance v s input current transfer curves ar e given for

the following light adapt condit ions:

(1) 25°C — 24 hour s @ no in put

(2) 25°C — 24 hour s @ 40 mA in put

(3) +50°C — 24 hours @ 40 mA input

(4) –20°C — 24 hour s @ 40 mA input

3. Response time characteristics are based u pon te st followi ng

adapt condition (2) above.

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Low Cost Axial Vactrols VTL5C3, 5C4

PA CKAGE DIMENSIONS INCH (MM)

PLASTIC POTTI NG CONTOUR

NOT CONT ROLLED

DESCRIPTION

VTL 5C 3 has a st ee p s lope, go od dyna mi c rang e, a ver y l ow t empe rat ure coe ffic ien t o f r esi stanc e, a nd a sma ll li ght hi stor y mem or y.

VTL5C4 features a very low “on” resistance, fast response time, with a smaller temperature coefficient of resistance than VTL5C1.

ABSOLUTE MAXIMU M RATIN G S @ 25°C

Maximum Temperatures

Storage and Opera ti ng: –4 0°C to 75°C

Cell Power: 175 mW

Der ate above 30°C: 3.9 m W/°C

LED Current: 40 mA

Der ate above 30°C: 0.9 m A/ °C

LED Reverse Br eakdown Volt age: 3.0 V

LED Forward Voltage Drop @ 20 mA: 2.0V (1.65V Typ.)

Min . Is olation Voltage @ 70% Rel. Humidity: 25 00 VR MS

Out put Cel l C apacitance: 5.0 pF

Cell Voltag e: 25 0V ( VT L5C3),

50 V ( VTL5C4)

Input - Output Cou pli ng Capacit ance: 0.5 pF

ELECTRO-OPTICAL CHARCTERISTICS @ 25°C

Refer to Specification Notes, page 41.

Part

Number Material

Type

ON Resistance OFF

Resistance

@ 10 se c. (Mi n . )

Slope

(Typ.)

Dynamic Range

(Typ.) Response Time

Input current Dark

Adapted

(Typ.)

Tu rn-on to

63% Final RON

(Typ.)

Turn-off (Dec ay)

to 100 kΩ

(Max.)

VTL5C3 3 1 mA

10 mA

40 mA

30 kΩ

5 Ω

1.5 Ω10 MΩ20 75 db 2.5 ms 35 ms

VTL5C4 4 1 mA

10 mA

40 mA

1.2 kΩ

125 Ω

75 Ω400 MΩ18.7 72 db 6.0 ms 1.5 sec

R@ 0.5 mA

R@ 5 mA

------------------------- RDARK

R@ 20 mA

------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Typical Performance Curves

Output Resistance vs. Input Current

VTL5C3

Output Resistance vs. Input Current

VTL5C4

Input Charact eristics

Response Time

VTL5C3

Response Time

VTL5C4

Notes:

1. At 1. 0 mA and below, uni ts may ha ve substanti ally higher

resi stance than shown in the typ ical curv es. Consul t factory if

closely controll ed characterist ics are required at low input

currents.

2. Out put resistance v s input current transfer curves ar e given for

the following light adapt condit ions:

(1) 25°C — 24 hour s @ no in put

(2) 25°C — 24 hour s @ 40 mA in put

(3) +50°C — 24 hours @ 40 mA input

(4) –20°C — 24 hour s @ 40 mA input

3. Response time characteristics are based u pon te st followi ng

adapt condition (2) above.

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Dual Element Axial Vactrols VTL5C2/2, 5C3/2

PA CKAGE DIMENSIONS INCH (MM)

PLAST IC POT TING CONTOUR

NOT CONTROLLED

DESCRIPTION

VTL5C 2/2 fe atures a very steep slope, low temperat ur e coefficient of resistance , and a small light history memory.

VTL5C 3/2 has a steep sl ope, good dynamic range, a very low temperatur e coeffi cient of resist ance, and a small light hist ory memory.

ABSOLUTE MAXIMU M RATIN G S @ 25°C

Maximum Temperatures

Storage and Opera ti ng: –4 0°C to 75°C

Cell Power: 175 mW

Der ate above 30°C: 3.9 m W/°C

LED Current: 40 mA

Der ate above 30°C: 0.9 m A/ °C

LED Reverse Br eakdown Volt age: 3.0 V

LED Forward Voltage Drop @ 20 mA: 2.0V (1.65V Typ.)

Min . Is olation Voltage @ 70% Rel. Humidity: 25 00 VR MS

Out put Cel l C apacitance: 5.0 pF

Cell Voltage: 50V (VTL 5C2/2),

10 0V (VTL5C2/ 3)

Input - Output Cou pli ng Capacit ance: 0.5 pF

ELECTRO-OPTICAL CHARCTERISTICS @ 25°C

Refer to Specification Notes, page 41.

Part

Number Material

Type

ON Resistance OFF

Resistance

@ 10 se c. (Mi n . )

Slope

(Typ.) Dynamic Range

(Typ.) Response Time

Input current Dark

Adapted

(Typ.)

Tu rn-on to

63% Final RON

(Typ.)

Turn-off (Dec ay)

to 100 kΩ

(Max.)

VTL5C2/2 Ø 5 mA

40 mA 2.5 kΩ

700 Ω1.0 MΩ20 65 db 7.0 ms 150 ms

VTL5C3/2 3 1 mA

40 mA 55 kΩ

2 Ω10 MΩ19 71 db 3.0 ms 50 ms

@ 0.5 m A

R@ 5 mA

------------------------ RDARK

R@ 20 mA

------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Typical Performance Curves

Output Resistance vs. Input Current

VTL5C2/2

Output Resistance vs. Input Current

VTL5C3/2

Input Charact eristics

Response Time

VTL5C2/2

Response Time

VTL5C3/2

Notes:

1. At 1. 0 mA and below, uni ts may ha ve substanti ally higher

resi stance than shown in the typ ical curv es. Consul t factory if

closely controll ed characterist ics are required at low input

currents.

2. Out put resistance v s input current transfer curves ar e given for

the following light adapt condit ions:

(1) 25°C — 24 hour s @ no in put

(2) 25°C — 24 hour s @ 40 mA in put

(3) +50°C — 24 hours @ 40 mA input

(4) –20°C — 24 hour s @ 40 mA input

3. Response time characteristics are based u pon te st followi ng

adapt condition (2) above.

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Dual Element Axial Vactrols VTL5C4/2

PA CKAGE DIMENSIONS INCH (MM)

PLASTIC POT TING CONTOUR

NOT CONTROLLED

DESCRIPTION

VTL5C4/2 features a very low “on” resistance, fast response time, with a smaller temperature coefficient of resistance than VTL5C1.

ABSOLUTE MAXIMU M RATIN G S @ 25°C

Maximum Temperatures

Storage and Opera ti ng: –4 0°C to 75°C

Cell Power: 175 mW

Der ate above 30°C: 3.9 m W/°C

LED Current: 40 mA

Der ate above 30°C: 0.9 m A/ °C

LED Reverse Br eakdown Volt age: 3.0 V

LED Forward Voltage Drop @ 20 mA: 2.0V (1.65V Typ.)

Min . Is olation Voltage @ 70% Rel. Humidity: 25 00 VR MS

Out put Cel l C apacitance: 5.0 pF

Cell Voltag e: 30 V

Input - Output Cou pli ng Capacit ance: 0.5 pF

ELECTRO-OPTICAL CHARCTERISTICS @ 25°C

Refer to Specification Notes, page 41.

Part

Number Material

Type

ON Resistance OFF

Resistance

@ 10 sec. (Min.)

Slope

(Typ.) Dynamic Range

(Typ.) Response Time

Inpu t c u r re n t Dark

Adapte d

(Typ.)

Turn-on to

63% Final RON

(Typ.)

Turn-off (Decay)

to 100 kΩ

(Max.)

VTL5C4/2 4 1 mA

10 mA 1.5 kΩ

150 Ω400 Ω8.3 68 db 6. 0 ms 1.5 sec

@ 0.5 m A

R@ 5 mA

------------------------ RDARK

R@ 20 mA

------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Typical Performance Curves (Per Element)

Output Resistance vs. Input Current

VTL5C4/2

Input Charact eristics

Response Time

VTL5C4/2

Notes:

1. At 1. 0 mA and below, uni ts may ha ve substanti ally higher

resi stance than shown in the typ ical curv es. Consul t factory if

closely controll ed characterist ics are required at low input

currents.

2. Out put resistance v s input current transfer curves ar e given for

the following light adapt condit ions:

(1) 25°C — 24 hour s @ no in put

(2) 25°C — 24 hour s @ 40 mA in put

(3) +50°C — 24 hours @ 40 mA input

(4) –20°C — 24 hour s @ 40 mA input

3. Response time characteristics are based u pon te st followi ng

adapt condition (2) above.

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Low Cost Axial Vactrols VTL5C6, 5C7

PA CKAGE DIMENSIONS INCH (MM)

PLASTIC POTTI NG CONTOUR

NOT CONT ROLLED

DESCRIPTION

VTL5C6 has a large dynamic range, high dark resistance, a low temperature coeffecient of resistance, and a small light history

memory. VTL5C7 is a shallow sloped device with good dynamic range, average temperature coefficient of resistance, speed of

response, and light history memory.

ABSOLUTE MAXIMU M RATIN G S @ 25°C

Maximum Temperatures

Storage and Opera ti ng: –4 0°C to 75°C

Cell Power: 175 mW

Der ate above 30°C: 3.9 m W/°C

LED Current: 40 mA

Der ate above 30°C: 0.9 m A/ °C

LED Reverse Br eakdown Volt age: 3.0 V

LED Forward Voltage Drop @ 20 mA: 2.0V (1.65V Typ.)

Min . Is olation Voltage @ 70% Rel. Humidity: 25 00 VR MS

Out put Cel l C apacitance: 5.0 pF

Cell Voltag e: 25 0V ( VT L5C6),

50 V ( VTL5C7)

Input - Output Cou pli ng Capacit ance: 0.5 pF

ELECTRO-OPTICAL CHARCTERISTICS @ 25°C

Refer to Specification Notes, page 41.

Part

Number Material

Type

ON Resistance OFF

Resistance

@ 10 se c. (Mi n . )

Slope

(Ty p.)

Dynamic Range

(Typ.) Response Time

Input

current

Dark

Adapted

(Typ.)

Tur n-on to

63% Final RON

(Typ.)

Tu rn- of f (Decay)

to (M ax .)

1 MΩ100 kΩ

VTL5C6 0 1 mA

10 mA

40 mA

75 kΩ

10 kΩ

2 kΩ100 MΩ16.7 88 db 3.5 ms 50 ms

VTL5C7 7 0.4 m A

2 mA 5 kΩ

1.1 kΩ1 MΩ5.7 75 db 6.0 ms 1 sec

@ 0.5 m A

R@ 5 mA

------------------------ RDARK

R@ 20 mA

------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Typical Performance Curves

Output Resistance vs. Input Current

VTL5C6

Output Resistance vs. Input Current

VTL5C7

Input Charact eristics

Response Time

VTL5C6

Response Time

VTL5C7

Notes:

1. At 1. 0 mA and below, uni ts may ha ve substanti ally higher

resi stance than shown in the typ ical curv es. Consul t factory if

closely controll ed characterist ics are required at low input

currents.

2. Out put resistance v s input current transfer curves ar e given for

the following light adapt condit ions:

(1) 25°C — 24 hour s @ no in put

(2) 25°C — 24 hour s @ 40 mA in put

(3) +50°C — 24 hours @ 40 mA input

(4) –20°C — 24 hour s @ 40 mA input

3. Response time characteristics are based u pon te st followi ng

adapt condition (2) above.

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Low Cost Axial Vactrols VTL5C8

PA CKAGE DIMENSIONS INCH (MM)

PLASTIC POTTI NG CONTOUR

NOT CONT ROLLED

DESCRIPTION

VTL5C8 is similar to VTL5C2 with a low t emperature coef ficient of resistance and little light history memor y, but has a more shallow

slope and a lower “on” resi stance at low (1 mA) drive cur r ents.

ABSOLUTE MAXIMU M RATIN G S @ 25°C

Maximum Temperatures

Storage and Opera ti ng: –4 0°C to 75°C

Cell Power: 175 mW

Der ate above 30°C: 3.9 m W/°C

LED Current: 40 mA

Der ate above 30°C: 0.9 m A/ °C

LED Reverse Br eakdown Volt age: 3.0 V

LED Forward Voltage Drop @ 20 mA: 2.8V (2.2V Typ.)

Min . Is olation Voltage @ 70% Rel. Humidity: 25 00 VR MS

Out put Cel l C apacitance: 5.0 pF

Cell Voltag e: 50 0V

Input - Output Cou pli ng Capacit ance: 0.5 pF

ELECTRO-OPTICAL CHARCTERISTICS @ 25°C

Refer to Specification Notes, page 41.

Part

Number Material

Type

ON Resistance OFF

Resistance

@ 10 sec. (Min.)

Slope

(Typ.) Dynam ic Range

(Typ.) Response Time

Inpu t c u r re n t Dark

Adapte d

(Typ.)

Turn-on to

63% Final RON

(Typ.)

Turn-off (Decay)

to 100 kΩ

(Max.)

VTL5C8 0 1 mA

4 mA

16 mA

4.8 kΩ

1.8 kΩ

1.0 kΩ10 MΩ8 80 db 4 ms 60 ms

@ 0.5 m A

R@ 5 mA

------------------------ RDARK

R@ 20 mA

------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Typical Performance Curves

Output Resistance vs. Input Current

VTL5C8

Input Charact eristics

Response Time

VTL5C8

Notes:

1. At 1. 0 mA and below, uni ts may ha ve substanti ally higher

resi stance than shown in the typ ical curv es. Consul t factory if

closely controll ed characterist ics are required at low input

currents.

2. Out put resistance v s input current transfer curves ar e given for

the following light adapt condit ions:

(1) 25°C — 24 hour s @ no in put

(2) 25°C — 24 hour s @ 40 mA in put

(3) +50°C — 24 hours @ 40 mA input

(4) –20°C — 24 hour s @ 40 mA input

3. Response time characteristics are based u pon te st followi ng

adapt condition (2) above.

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Low Cost Axial Vactrols VTL5C9, 5C10

PA CKAGE DIMENSIONS INCH (MM)

PLASTIC POTTI NG CONTOUR

NOT CONT ROLLED

DESCRIPTION

VTL5C9 has a 112 db dynamic range, fast response time, high dark resistance, but with a more shallow slope and lower “on”

resis tance a t l ow (1 mA) drive curre nts than the VTL5C1. VTL510 offers a low “on” resis tance at low dr ive cur rents, a fast res ponse

tim e, and has a small er t em perat ure c oe f fic i ent than t he VTL5C 9.

ABSOLUTE MAXIMU M RATIN G S @ 25°C

Maximum Temperatures

Storage and Opera ti ng: –4 0°C to 75°C

Cell Power: 175 mW

Der ate above 30°C: 3.9 m W/°C

LED Current: 40 mA

Der ate above 30°C: 0.9 m A/ °C

LED Reverse Br eakdown Volt age: 3.0 V

LED Forward Voltage Drop @ 20 mA: 2.8V (2.2V Typ.)

Min . Is olation Voltage @ 70% Rel. Humidity: 25 00 VR MS

Out put Cel l C apacitance: 5.0 pF

Cell Voltag e: 10 0V ( VT L5C9),

50 V ( VTL5C10)

Input - Output Cou pli ng Capacit ance: 0.5 pF

ELECTRO-OPTICAL CHARCTERISTICS @ 25°C

Refer to Specification Notes, page 41.

Part

Number Material

Type

ON Resistance OFF

Resistance

@ 10 sec. (Min.)

Slope

(Typ.) Dynamic Range

(Typ.) Response Time

Inpu t c u r re n t Dark

Adapte d

(Typ.)

Turn-on to

63% Final RON

(Typ.)

Turn-off (Decay)

to 100 kΩ

(Max.)

VTL5C9 1 2 mA 630 Ω50 MΩ7.3 112 db 4.0 ms 50 ms

VTL5C10 4 2 mA 400 Ω400 K Ω3.8 75 db 1.0 ms 1.5 sec

@ 0.5 m A

R@ 5 mA

------------------------ RDARK

R@ 20 mA

------------------------

PerkinElmer Optoelectronics, 10900 Page Ave., St. Louis, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Typical Performance Curves

Output Resistance vs. Input Current

VTL5C9

Output Resistance vs. Input Current

VTL5C10

Input Charact eristics

Response Time

VTL5C9

Response Time

VTL5C10

Notes:

1. At 1. 0 mA and below, uni ts may ha ve substanti ally higher

resi stance than shown in the typ ical curv es. Consul t factory if

closely controll ed characterist ics are required at low input

currents.

2. Out put resistance v s input current transfer curves ar e given for

the following light adapt condit ions:

(1) 25°C — 24 hour s @ no in put

(2) 25°C — 24 hour s @ 40 mA in put

(3) +50°C — 24 hours @ 40 mA input

(4) –20°C — 24 hour s @ 40 mA input

3. Response time characteristics are based u pon te st followi ng

adapt condition (2) above.

Perk inElmer Optoelectronics, 10900 Page Ave., St. Lou is, MO 63132 USA Phone: 314-423-4900 Fax: 314-423-3956 Web: www.perkinelmer.com/opto

Application Notes—Analog Optical Isolators

APPLICATION NOTE #1 Audio Applications

The LDR output element of AOIs is almost purely resistive in nature.

This property makes the AOI a ver y useful device for the control of AC

signals. Further, because AOIs also possess very low noise and low

harmonic distortion characteristics, they are ideal for use as variable

resistors, capable of being remotely adjusted in a wide range of audio

ap pli cations and control c irc uits.

The focus of this note is on the use of AOIs in audio applications.

However, many of the approaches used are equally applicable to

higher frequency AC amp lifi cation and cont r ol cir cuit s.

Control Circuits

Vo ltag e Divide r Ci rc uits

The output element of the AOI is a two terminal variable resistor and

ma y be used in a voltage divider cir cuit as shown in Figures 1a and 1b.

Shunt Input Control

Figure 1a shows the AOI as the shunt element. With I

= 0, the

photocell has a very high r esistance so e

out

= e

. When I

i s inje cte d

into the LED, the AOI output resistance decreases pulling down the

out put voltage. S ince the cell cannot be driven to zero resistance, the

v alue of R

mu st be select ed to give the desired m aximum attenuation.

A VTL5C4 with a maximum “on” resistance of 200 ohms at I

= 10 mA

requires an R

of 6100 ohms for 30 db voltage attenuat ion (pr oducing

a 1 000: 1 power rati o). The actual atte nuation r atio will be gr eater si nce

the 10 mA “ on” resistan ce is t y pically 125 ohms.

When the maximum I

is less than 10 mA, the series resistance must

be greater to get the same attenuation ratio. If R

is made large, the

insertion lo ss (db atten uation at I

= 0) wi ll be higher when the out put is

loaded. The maximum voltage across the photocell in this circuit is

equal to the input voltage assuming no insertion loss. An input voltage

as high as 5 – 10V will produce noticeable distortion but that will drop

as I

is increased. To minimize distortion, the voltage across the cell

sh ould be kept below 1.0V at th e normal op er ating point.

Series Input Contro l

With an AOI as the series element as shown in Figure 1b, e

out

=0 at I

= 0. The maximum voltage across the cell is e

, but decrea ses as I

increases.

Op-Amp Feedback Resistor Control

The AOI may also be used as the input or feedback resistor of an

operational amplifier. When used in the feedback loop, Figure 1c, a

fixed resistor should be used in parallel. With no parallel limiting

resistor, the feedback may approach an open circuit condition at

maximum gain. In this open loop state, the circuit becomes unstable

and may latch up. The parallel resistor R

sets the maximum gain of

the amplifier and stabilizes the DC output voltage. Resistor R

is in

se ries with the AOI out put and sets the minim um gain of the ci rc uit . For

op-amps with unity gain compensation, R

is set equal to R

so the

cir c uit gain doe s not dro p below one. The maximum voltag e on t he cell

(LDR) is e

out

. If minimizing distortion is a consideration, e

out

should be

k ept below 1.0V.

Op-Amp Input Resistor Control

When t he AOI is used as the input resistor of an op-amp, Figure 1d, a

fixed resistor in series will limit the maximum gain as well as prevent

overload of the previous stage.

Non-Inverting Op-Amp Circuits

The AOI can also be used in non-inverting op-amp circuits. Gain is

controlled potentiometrically and, again, resistors should be used to

limit the maximum gain. The circuit of Figure 1e requires a resistor in

series with the AOI, while the circuit of Figure 1f requires one in

parallel.

General Considerations

The ci rcuit application and AOI character istics will influence the choice

of circuit to use. In Figure 1a to 1f, gain vs. I

curves are giv en for each

cir c uit, a s well as inpu t impedance and gain formulas. Once the pr oper

circuit function is selected, AOI response speed must be considered.

Because an LDR (photocell) turns “on” fast and “off ” slowly, circuits of

Figure 1d and 1e will increase in gain rapidly but be slower in the

decreasing gain. The circuits of Figure 1c and 1f respond faster when

the gain is reduced. All other design considerations are the same as

they w ould be for any op-amp circuit. In all the amplifier configurations,

a ga in ratio of 1000 :1 or hi gher can be achieved.

Application Notes—Analog Optical Isolators

Basic Circuit Configuration Input

Resistance Gain

Figure 1a. Shunt Input Con trol

Variable

Figure 1b. Series Input Control

Variable

Figure 1c. Feedback Resistor Control

F i xed, Low

eout

ein

-----------

RLDR()

R1RLDR()

---------------------------

R1RLDR()

---------------------------

R3RLDR R2

+[]

1RLDR R2R3

++[

]

--------------------------------------------

Application Notes—Analog Optical Isolators

Basic Circuit Configuration Input Resistance Gain

Figure 1d. Input Resistor Control

Variable

Figure 1e. Potentiometric Gain

Fixed, High

Figure 1f. Potentiome tric Gain

Fixed, High

RLDR()

---------------------------

1R1

RLDR()

---------------------------+

R1RLDR()

R2RLDR()

--------------------------------------+

Application Notes—Analog Optical Isolators

Switching

Mechanical switching of low level audio signals requires the use of

switches with precious metal contacts. Sudden changes in signal can

cause the speakers to thump and damage may occur if the speaker is

underdamped. A simple way to avoid these problems is to use an AOI

in place of a mechanical switch. In the circuit of Figure 1d, the initial

resistance of the LDR cell is so high that amplifier gain is essentially

zero. A step change in forward current through the LED is translated

into a slower time change in the cel l resistance. The resistance drops

to 10 times the final value in one millisecond or less. As t he resistance

cont inues to drop, the final value is approached exponentially. Express

in terms of conductivity:

where:

G = conductance , mhos

t = tim e , ms

tc = ti m e constance of the photocell, ms

If R1 is made equal to nine times the final value of resistance, the

response to 50% signal will occur in 1.0 ms. The time to get to within

0.5 db of full signal is one time constant, which is usually only a few

mi ll iseconds . The step change of a switch has been tra nsformed into a

rapid but smooth increase in signal level. In addition, the possibility of

turn-on in the mi ddle of a peak has been eliminat ed.

Turn-off is slower and depends on the ratio of R1 to the final value of

ph ot ocell resis tance. A high r ati o wi ll slow dow n the turn-off and speed

up the turn-on.

This circuit can be extended into a matrix as shown in Figure 2. Whi le

a 3 x 3 matrix is shown, the number of nodes is not limited. Individual

inputs can be summed into a single output or connect ed to more than

one output. A matrix can be made very compact with the output

amplifiers mounted very close to reduce pickup. The op-amps

eliminate any crosstalk between the inputs since the summ ing point is

at virtual g ro und.

The controls for the matrix are usually remotely located. The DC

current through the LEDs may be controlled by switches, manual

po te ntiometer s, or a computer. Th e m atrix may be used for s imple ON-

OFF gating, summing of several signals, or proportional control. When

proportional control is used, the output should be continuously

supervised to correct for changes in signal level due to photocell

resistance variation from temperature, light adapt history, and self

heating.

Figure 2. Switching Ma trix

01 exp t–tc⁄()–[] mhos=

and: R 1 G ohms⁄=

Application Notes—Analog Optical Isolators

Gating and Muting

Background noise becom es very objectionab le when a signal l evel in a

program is low. Noise is any unwanted sound and may be due to tape

hiss or am plif ier hum . These noises can be eli m inated by selective use

of gating and muting, that is, turning the amplifier on when the signal

level is high and of f when it is low. This technique can also remove or

reduce unwanted echo, prin t through, pre s ence or any other distracting

signal during portions of a program which are normally silent. The

gating circuit must be completely transparent to the listener, having a

smo oth, rapid operation with no signal distortion.

A practical gating circuit having these features is shown in Figure 3.

The circuit has five basic sections: the threshold adjust m ent, a hi gh AC

gain stage, full-wave rectifier, LED driver and an electrically controlled

voltage divider. When the signal is below the threshold level, the

voltage divider consisting of the AOI and R

has maximum

att enuat ion. When the signal e xceeds th e thr eshold, the vol tage divider

allows the signal to pass thro ugh.

The circuit operation is as follows. The THRESHOLD potentiometer

applies a portion of the signal to the high gain AC amplifier consisting

of op-amp A

, resistors R

and R

and capacitor C

. The amplified

signal is full-wave rect ified by diodes D

and D

together with op-amp

which inverts the negative half of the signal. The rectifier charges

used for RELEASE TIME control and drives the base of transistor

, the LED driver. The threshold voltage is a sum of the forward drop

of the rectifying diodes, the voltage drop across R

, V

or Q

and V

of the LED. This voltage is 2.5 – 3.0V and when referred to the input

gives a threshold of 2.5 – 3.0 mV at t he am plif ier.

The circuit can be set up for a specified threshold voltage. Release

time is usually determined empirically. A typical set up procedure uses

an audio signal containing spoken dialog. Initially, the THRESHOLD

adjustment is set to the maximum and the RELEASE is set to the

minimum. The program is turned on and the THRESHOLD is

decreased until the audio star ts coming through, but sounds chopped

up. The chopping occur s because the circuit is too f ast on r elease. The

RELEASE is increased until the audio is smoothed out and sounds

normal. Setting of the two controls needs to be made carefully. A

thr eshold set too hig h cuts off the quiet er sounds, whi le a setting which

is too low al lows m or e of the noise to come thr ough. Short rel ease tim e

causes more chopping of the audio and can create some distor tion at

the lower frequencies . Long releas e ti m e keeps the gate open too lo ng

allowing noise to come through after the signal is gone. Adjustments

should be made incrementally and worked between the two controls

un ti l t he best sound is achi eved.

Figure 3. Audio Sound Gate

Application Notes—Analog Optical Isolators

Limiters

If the magnitude of an AC signal varies over a wide range, it may be

necessary to amplify or compress the signal before any audio

processing can be performed. In other cases, the audio power has to

be limited to prevent damage to an output device. Circuits that perform

this funct ion on a continual basis need a non-linea r element to produce

variable gain. However, most non-linear elements introduce distor tion.

This is unacceptable in a high fidelity audio circuit and other critical

ap pli cations. Usi ng an AOI , simple cir c uits can be made to perf orm this

funct ion without introducing distortion or generati ng any noise.

Signal Lim iters

Any circu it that performs as a lim it er or compressor must have low gain

when the signal magnitude is high and high gain when the signal is

low. The gain is adjusted so t hat a wide dynamic range is compressed

into a small one. In other signal processing applications, the signal

may need t o be virtually constant.

The circuit such as shown in Figure 4a will keep the output level

constant when the input voltage varies over a range of 50 – 60db.

Am pli fier A1 operates as an inv erting amplif ier with a gain :

out

/ e

= R

PHOTOCELL

/ R

The feedback resistor is a photocell and has an “off ” resistance of 10

meg ohm s, mi nimum, and an “on” re sist ance of 5000 ohms with 5.0 mA

in the LED. Using the components shown, the gain of this stage var ies

bet ween 500 with no signal and 0.5 with maximum signal applied. R

limits the maximum gain and is needed to prevent the amplifier, A

from going open loop when there is no input signal, in which case the

cel l “off” resistance is much higher than 10 M

Ω

Amplifier A

operates as a high input impedance rectifier that drives

the LED. The forward dro p of the LED i s 1.6 – 2.0V, and when the peak

output of the rectifier exceeds this value, current will flow into the LED.

As the signal increases, more current flows into the LED, driving the

photocell resistance lower thus decreasing the amplifier gain. The

ou tput of A

is regul ated at a v oltage determin ed by the forward dro p of

the LED and the closed loop gain of amplifier A

. A

amplifies the

signal by a factor of two, and a 1.8V peak (1.27 VRMS) is required to

activate this AOI. This results in the output voltage being held to 0.64

VRMS over a input range of 1 – 600 mV. Changing the value of R

changes the gain of the rectifier. Omitting R

will double the output

voltage because the rectifier gain drops to one. Putting a resistor in

se ries wi th the LE D will cause the r egulated voltage to rise as t he input

is increased (see Figure 4b). As the amplifier gain changes, the

amp lifi er bandwidth also changes . When the signal is low, the ampl ifier

wil l have the highest gain a nd lowest bandwidth .

Figure 4a. Peak Sensing Compressor Figure 4b. Output Characteristics

Application Notes—Analog Optical Isolators

Figure 5. Peak Sensing Compressor with Constant Bandwidth

Variable bandwidth can be avoided if the AOI is used in a voltage

divider circuit at the input of a fixed gain amplifier. For the same range

of input signals, the amplifier gain must be 500 and the voltage divider

must have a range of 1000:1. This configuration is show n in Figure 5.

The AOI has been changed to a lower resistance unit to be able to

work over the wider range. Also, A

is now a high input impedance,

non-inverting stage to avoid a high insertion loss. This circuit is usef ul

when the input voltage is high, which allows the use of a lower gain

amplifier.

Speaker Power Limiting

Speakers that are driven from high pow er amplifiers mu st be pr ot ected

from excess drive. While ordinary program levels may be well within

the rating of the speaker, peaks do occur that can be destructive. The

simplest solution is to use a compressor or limiter. Unfortunately, the

maximum power that may be applied is not constant over the

frequency range. Therefore, t he limit must be set to provi de prot ection

at th e lowest frequency that i s expected.

To under stand the requ ir em ents for effective speak er protect ion, a brief

review of speaker power limitations follows. Figure 7 is a typical

maximum sine wave voltage limit for a low frequency speaker

commonly called a “woofer”. Above 200 Hz, the maximum allowed

voltage or power is constant. The operating temperat ure at which wire

insulation and coil bonding fail establishes this value. Below 200 Hz,

the voltage limit is determined by the allowable diaphragm excursion.

For constant voltage on the speaker, the displacement doubles when

the frequency is reduced by half. The maximum displacement is

determined by the mechanical design of the speaker and exceeding

the limit will produce extreme distortion and may even cause

mechanical damage.

Figure 7. Maximum sine wave Voltage and Po wer for a Ty pical W o ofer

Application Notes—Analog Optical Isolators

This reduced low frequency power rating can be accommodated by

using a limited circuit which reduces the limit threshold when the

fr equency is below 200 Hz. Figure 8a shows a ve ry simpl e cir cuit to do

this. At low frequency, the gain of amplifier A

is unity. The amplifier

has a 6 db/octave gain roll-off starting at 25 Hz and levels off at 100

Hz. Therefore it will take a signal that is four times as large at 100 Hz

as at 25 Hz before limiting action start s. Breakpoints in the Frequency

vs. Gain curve shown in Figure 8b can be set to match the speaker

frequency dependent power limit. Also, potentiometer R

c a n be s e t to

matc h the pow er ra ting and impedance of the speaker.

The threshold is set by the sum of V

of Q

and the forwar d voltage

drops of D

and the LED, app roximatel y 2.8V peak or 2. 0 VR M S. Once

the threshold has been exceeded, current is injected into the LED of

the AOI which attenuates the signal voltage. This voltage divider can

be placed anywhere in the signal path. Once the limiter comes into

play, the system frequency response will no longer be flat, but no

distortion is in troduced.

Automatic Gain Control

Automatic gain control (AGC) circuits have electrically programmable

references or set points, but in other respects are the same as limiters

or compressor circuits. Each has a forward gain amplifier and a loop

which controls the gain of that am plifi er.

Figure 8a. Speaker Power Limiter with Frequency Compensation

Figure 8b. Amplitude vs. Frequency for the Amplifier Figure 8c. System Voltage Limits

Application Notes—Analog Optical Isolators

Figure 9 shows an AG C circuit which consists of three main element s:

a variable gain amplifier, full-wave active rectifier and a summing

amplifier. The variable gain amplifier consists of op-amp A1 with

pot entiometric gain that is controlled by the resistance of the photocell

of the AOI. The gain of this am pli fier is:

Gain = 1 + R

/ R

PHOTOCELL

With R

= 100k ohms, the minimum gain is one since the cell “off”

resistance is several megohms. The maximum gain in only 100 since

the resistance of a typical VTL5C2 is 1000 ohms at an input cur rent of

5.0 mA. If a range of 40 db (100:1) is not adequate, t here are several

opt ions. R

can be incr eased, the LE D drive current for the AOI can be

incr eased or a lower resistance AOI such as th e VTL5C4 can be used .

Amp lifie r A

together with diodes D

and D

and resistors R

, R

, and

form a full-wave rectifier. The amplifier has a gain of one so the

out put is equal to the rectified input. There is no offset due to rectifier

forward drops so this circuit will recti fy signal s all the w ay do wn to zero

volts. Since the DC output of A

is not referenced to ground, op-amp

and resistors R

, R

, and R

form a fully differential amplifier

which shifts the DC reference to ground.

Op-amp A

is used as an integrator. The signal from the full-wave

rectifier is summed with a reference vol tage V

REF

and integrated. The

time constant of the integrator is selected to limit the bandwidth of the

control loop as well as assure stability of the loop. If the bandwidth is

too wide, the control loop will follow the signal on an instantaneous

ba sis. The AOI alone is not very f ast, b ut signals with f requencies of 30

– 60 Hz coul d be distorted if ther e w ere no time del ay in the inte gr ator.

The AGC circuit operates as follows. When there is no signal, the

negative V

REF

causes A

to be at a maximum positive output.

Maximum forwar d current is injected into the LED, driving the cell to a

low resistance and the gain of A

to the maximum where it stays until

ther e is a signal. A si gnal at the input terminal is am plified, r ectif ied a nd

algebraically summed with V

REF

at the inverting terminal of the

integrator. The cont rol loop will then act to make the absol ute value of

the re cti fied sign al equal to the reference voltage. V

REF

may be a fixed

v alue or a fun cti on of s om e other param et er.

Electrically Controlled Gain

The gain of an amplifier can be electrically programmed using the

cir c uit of Figure 10. An AOI with a center t apped photocell is used, one

side in the signal amplifier channel and the other in the control loop.

The signal amplifier consists of op-amp A

, r esistors R

and R

whic h

se t the gain and the input res ist or R

. The gain of this amplifier i s giv en

by:

Figure 9. AGC Circuit with Electrical Setpoint

Geout

ein

-------- R2R3

+()

----------------------==

Application Notes—Analog Optical Isolators

The cont rol loop consi sts of op-amp A

and resistors R

and R

. Thi s

cir cuit sets the LED current so that :

If we set: R

= R

and: R

= R

then: e

out

/ e

= V

REF

/ V

or: e

out

= e

REF

/ V

)

where V

= cont rol voltage

Note th a t R

and R

are the two halves of the cell. These tw o re sist ors

match within 10% and track over a wide range within 5% so that the

gain i s close ly set by V

when V

REF

is fix ed.

The limits of ope ration are:

0 < V

< V

REF

and the signal must never be so large that am plifier A

sa tu ra tes whe n

the gain is at maximum.

This circuit performs a dividing operation with e

and V

as the

numerator and denominator respectively. The accuracy is limited by

the tracking ability of the two sides of the photocell. The error due to

matching can be elim inated by trimming R

Figure 10. Electrically Programmab le Gain

VREF

-----------R1R4

+()

----------------------=

eout

ein

-------- VREF

-----------Gain==

Application Notes—Analog Optical Isolators

APPL IC ATION N OTE #2

Handling and Soldering AOIs

All opto components must be handled and soldered with care,

especially those that use a cast or molded plastic and lead frame

construction li ke the LE Ds used in A O Is.

In LED lead frame construction, the emitter chip is mounted directly to

one lead and a wire bond is made f rom the chi p to the ot her lead. The

encapsulating plastic is the onl y support for the l ead frame. Care must

be taken when forming the leads of plastic opto packages. Excessive

mechanical force can cause the leads to move inside the plastic

package and damage the wire bonds. Weakened bonds can then

“open up” under further mechanical or thermal stressing, producing

op en circuits.

In order to form leads safely, it is necessary to firmly lamp the leads

near the base of the package in order not to transfer any force

(particularly tension forces) to the plastic body. This can be

accomplished either through use of properly designed tooling or by

firmly gripping the leads below the base of the package with a pair of

ne edle nose plie rs w hile the leads are being bent.

Exa mp les of Tooling Fixtures Use d to Form Lead s

For highest re liabili ty, av oid flush mounting the A OI body on the printed

circuit board. This minimizes mechanical stress set up between the

circuit board and the LED and photocell packages. It also reduces

so lder head damage to th e packages.

Good printed circuit board layout avoids putting any spreading (plastic

un der tension) force on t he leads of the LED and photocell.

Wh en hand so ldering, it is important to lim it the maxim um temp er ature

of the iron by controlling the power. It is best if a 15W or 25W iron is

used. The maximum recommended lead soldering temperature (1/16"

from the case for 5 seconds) is 260°C. An RMA rosin core solder is

recommended.

Sn60 (60% tin / 40% lead) solder is recommended for wave sol dering

opto components into printed circuit boards. Other alternatives are

Sn62 and Sn63. The maximum recommended soldering temperature

is 260°C with a maximum duration of 5 seconds.

The amount of tarnish on the leads determines the type of flux to use

when soldering devices wit h silver plated leads.

Cleaners designed for the removal of tarnish from the leads of

electronic components are acidic and it is best to keep the immersion

time as short as possible (less than 2 seconds) and to immediately

wash all devices th oroughly in ten rinses of deioni zed water.

Condi t ion of Le ad s Recomm e nded Flux

Clear Bright Finish

(Tarnish Free) RMA - Mildly Activated

Dull Finish

(Minimal Tarnish) RMA - Mildly Activated

Light Yellow Tint

(Mild Tarnish) RA - Activated

Light Yellow / Tan Color

(Moderate Tarnish) AC - Water Soluble,

Organic Acid Flux

Dark Tan / Black Color

(Heavy Tarnish) Leads Need to be Cleaned

Prior to Soldering

Application Notes—Analog Optical Isolators

The best policy is one which prevents tarnish from forming. Tarnish,

whi c h is a c ompound formed wh en silver reacts w it h sulfur (A g

S), can

be prevented by keeping the components away from sulfur or sulfur

compounds. Since two major sources of sulfur are room air and paper

products, it is best to store the devices in pr otectiv e packaging such as

a “si lver saver” paper or tightly seal ed polyethylene bags.

After soldering, it is necessary to clean the components to r emove any

rosi n and ionic residues. For a list ing of recom m ended cleaning agents

please refer to Application Notes #3.

APPL IC ATION N OTE #3

Recommended Cleaning Agents

The construction of an AOI consists of a cast epoxy LED, ceramic

photocell, a molded case and epoxy as the end fill. This construction

allows a wide variet y of cle aning agents to be sued aft er soldering.

In many cases the devices will be exposed to a post solder cleaning

operation which uses one or more solvents to remove the residual

sold er flux and ionic contaminants. Only certain cleaning solvents are

co mpatibl e wi th t he plastics use d in th e AOI packages.

This listing of recommended/not recommended solvents represents

only a very small percentage of available chemical cleaning agents.

Even with this list of recommended solvents it is important to be aware

that:

1. Solvent exposure times should be as short as possibl e.

2. The exact requi re m ent of th e cleaning process will v ary from

cu sto me r to customer and applicat ion to appl ication.

3. Additiv es and concentrations will vary from supplier to supplier.

Because of these uncertainties, our recommendation is that all

cu stomers careful ly ev al uate their o wn cleani ng process and dr aw th eir

own conclusions about the effectiveness and reliability of the process.

PerkinElmer cannot assume any responsibility for damage caused by

the use of any of the solvents above or any other solvents used in a

cleani ng process.

Recommended Not Recommended

Arklone A Acetone

Arklone K Carbon Tetrachloride

Arklone F Meth yl Eth yl K etone

Blaco-Tron DE-15 Methylene Chloride

Blaco-Tron DI-15 Trichloroethylene (TCE)

Freon TE Xylene

Freon TES Trichloroethane FC-111

Freon TE-35 Trichloroethane FC-112

Freon TP Freon TF

Freon TF-35 Freon TA

Genesolv D Freon TMC

Genesolv DE-15 Freon TMS

Genesolv DI-15 Genesolv DA

Isopropyl Alcohol Genesolv DM

Wat er Genesolv DMS

PerkinElmer Optoelectronics warrants that all items sold will be free from defects in materials and

workmanship under normal use and service for a period of one year from the date of shipment. If

PerkinElmer Optoelectronics receives notice of such defects during the warranty period, PerkinElmer

Optoelectronics shall, at its option, repair or replace any defective components or credit the purchaser's

account with the purchase price paid. This warranty shall not apply to items that have been (a) subject

to misuse, neglect, accident, damage in transit, abuse or unusual hazard; (b) altered, modified or

repaired by anyone other than PerkinElmer Optoelectronics; or (c) used in violation of instructions

furnished by PerkinElmer Optoelectronics. The Buyer should contact PerkinElmer Optoelectronics for a

return authorization number prior to shipping returned parts.

The specific PerkinElmer Optoelectronics' products shown in this catalog are not authorized or

recommended for use as critical components in life support systems or in surgical implant devices

wherein a failure or malfunction of the PerkinElmer Optoelectronics product may directly threaten life or

cause personal injury. The Buyer agrees to notify PerkinElmer Optoelectronics of any such intended

application and to proceed only after receiving the expressed written approval of an officer of

PerkinElmer Optoelectronics. Additionally, the user of PerkinElmer Optoelectronics components in life

support or implant applications assumes all risks of such use and indemnifies PerkinElmer

Optoelectronics against all damages.

In order to provide the best possible products, PerkinElmer Optoelectronics reserves the right to change

specifications without prior notice. Information supplied in PerkinElmer Optoelectronics' catalogs, data

sheets, and other literature, and information supplied by PerkinElmer Optoelectronics' technical support

personnel is believed to be reliable, however, PerkinElmer Optoelectronics cannot assume responsibility

for omissions, errors, or misapplication of this information.

It is the responsibility of the Buyer to determine the suitability of PerkinElmer Optoelectronics/ products

and recommendations in his own specific application, particularly when the products are operated at or

near their maximum rating specifications. No license is granted by implication or otherwise of any

patent, copyright, or trademark right of PerkinElmer Optoelectronics or others.

PerkinElmer Optoelectronics' warranty, as stated above, shall not be affected or changed by, and no

obligation or liability shall grow out of, PerkinElmer Optoelectronics' providing technical advice or service

to the Buyer.

PERKINELMER OPTOELECTRONICS MAKES NO OTHER WARRANTIES, EXPRESSED OR

IMPLIED, AND EXPRESSLY EXCLUDES AND DISCLAIMS ANY W ARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. THE REMEDIES PROVIDED

HEREIN ARE THE BUYER'S SOLE EXCLUSIVE REMEDIES. PERKINELMER OPTOELECTRONICS

SHALL NOT BE LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL

DAMAGES, WHETHER BASED ON CONTRACT, TORT, OR ANY LEGAL THEORY. PERKINELMER

OPTOELECTRONICS' LIABILITY ON ANY CLAIM SHALL IN NO CASE EXCEED THE PRICE

ALLOCABLE TO THE ITEM WHICH GIVES RISE TO THE CLAIM.

PerkinElmer Optoelectronics

Warranty Statement

PerkinElmer Optoelectronics’ business is the design, development, and production of optoelectronic components

and assemblies. Our development and manufacturing activities focus on achieving and maintaining consistent

product quality and high levels of reliability. PerkinElmer produces devices and assemblies for the commercial,

industrial, automotive, and medical markets.

PerkinElmer ’s commitment to quality emphasizes designed-in quality, problem prevention, and closed loop cor-

rective action. This concept of quality is implemented through the use of fully documented procedures, in-

process monitoring and process control (including SPC), and 100% production testing of devices using state-of-

the-art automated test equipment. As a world class manufacturer, PerkinElmer ’s concept of product quality

includes Total Quality Management (TQM) and Just In Time (JIT) delivery.

Quality is a measure of how well a device conforms to its specifications. Reliability is a measure of how well a

device performs over time. PerkinElmer insures the reliability of its products by careful design and by the period-

ic testing of random samples taken from the manufacturing lines. Reliability tests include temperature cycles,

thermal shock, room ambient life tests, elevated temperature life tests, high and low temperature storage, tem-

perature/humidity tests, and water immersion.

PerkinElmer also performs special tests covering a wide range of environmental and life stress conditions to

support non-standard, custom applications. The information generated not only assures the customer that the

device will work well in a particular application, but also contributes to our data base for continual product

improvement.

Driven by our goal of continuous improvement and the needs of customers, PerkinElmer runs an active product

improvement program. PerkinElmer continuously evaluates new materials, manufacturing processes, and pack-

aging systems in order to provide our customers with the best possible product.

PerkinElmer ’s quality works: we are an ISO 9000 and QS 9000 certified supplier (ship to stock - no inspection

required) to a number of major customers.

Quality Statement

Additional Sensor Products Catalogs

USA:

PerkinElmer Optoelectronics

10900 Page Avenue

St. Louis, MO 63132

Phone: (314) 423-4900

Fax: (314) 423-3956

Europe:

PerkinElmer Optoelectronics

Wenzel-Jaksch-Str. 31

D-65199 Wiesbaden

Germany

Phone: +49 611 492 0

Fax: +49 611 492 170

Asia:

PerkinElmer Optoelectronics

Room 1404, Kodak House II

39 Healthy Street East

North Point, Hong Kong

Phone: 852 2590 0238

Fax: 852 2590 0513