VRE505KS - Apex Microtechnology

P r o d u c t I n n o v a t i o n F r o m VRE505

VRE505DS 1

compensation technique. Signicant improvements

have been made in other performance parameters as

well, including initial accuracy, warm-up drift, line regu-

lation, and long-term stability, making the VRE505 the

most accurate reference available.

For enhanced performance, the VRE505 has an exter-

nal trim option for users who want less than 0.01% ini-

tial error. For ultra low noise applications, an external

capacitor can be attached between the noise reduc-

tion pin and the ground pin. A reference ground pin is

provided to eliminate socket contact resistance errors.

The VRE505 is recommended for use as a reference

for 14, 16, or 18 bit D/A converters which require an

external precision reference. The device is also ideal

for calibrating scale factor on high resolution A/D con-

verters. The VRE505 offers superior performance over

monolithic references.

FEATURES

♦ +5 V Output, ± 1.0 mV (.02%)

♦ Temperature Drift: 1 ppm/ºC

♦ Low Noise: 3 μVP-P (0.1-10 Hz)

♦ Industry Standard Pinout: 8-pin Surface Mount

Package

♦ Excellent Line Regulation: 6 ppm/V Typ.

♦ Output Trim Capability

DESCRIPTION

The VRE505 is a low cost, high precision +5 V refer-

ence. The device is ideal for upgrading systems that

use lower performance references.

The device provides ultrastable +5 V output with ±0.5

mV (.01%) initial accuracy and a temperature coef-

cient of 0.6 ppm/ºC. This improvement in accuracy is

made possible by a unique, patented multipoint laser

Precision Voltage Reference

VRE505

Product Innovation From

Figure 1. BLOCK DIAGRAM

Model

Initial Error

(mV)

Temp. Coeff.

(ppm/ºC)

Temp. Range

(ºC)

VRE505K ±1.0 2.0 -40ºC to +85ºC

SELECTION GUIDE

8-pin Surface Mount

Package Style GF

http://www.cirrus.com

AUG 2009

APEX - VRE505DSREVC

P r o d u c t I n n o v a t i o n F r o m

VRE505

2 VRE505DS

1. CHARACTERISTICS AND SPECIFICATIONS

ELECTRICAL SPECIFICATIONS

VPS = +15V, T = +25ºC, RL = 10KΩ Unless Otherwise Noted.

Parameter Min Typ Max Units

ABSOLUTE RATINGS

Power Supply ±13.5 ±15 ±22 V

Operating Temperature -40 +85 ºC

Storage Temperature -65 +150 ºC

Short Circuit Protection Continuous

OUTPUT VOLTAGE

VRE505 +5.0 V

Temperature Sensor Voltage (Note 1) 630

OUTPUT VOLTAGE ERRORS

Initial Error (Note 2) ±1.0 mV

Warmup Drift 2 ppm

TMIN - TMAX (Note 3) 2.0 ppm/ºC

Long-Term Stability 6 ppm/1000hrs.

Noise (0.1 - 10Hz) (Note 4) 3 µVpp

OUTPUT CURRENT

Range ±10 mA

REGULATION

Line 6 10 ppm/V

Load 3 ppm/mA

OUTPUT ADJUSTMENT

Range 10 mV

POWER SUPPLY CURRENT (Note 5)

+PS 57mA

NOTES:

1. The temp. reference TC is 2.1 mV/ºC

2. The specied values are without external trim.

3. The temperature coefcient is determined by the box method using the following formula:

4. The specied values are without the external noise reduction capacitor.

5. The specied values are unloaded.

VNOMINAL x (TMAX – TMIN)

VMAX – VMIN

TC = x 106

P r o d u c t I n n o v a t i o n F r o m VRE505

VRE505DS 3

2. TYPICAL PERFORMANCE CURVES

Temperature

VRE505K

OUT

vs. TEMPERATURE

QUIESCENT CURRENT VS. TEMP

Temperature

JUNCTION TEMP. RISE VS. OUTPUT CURRENT

Output Current (mA)

PSRR VS. FREQUENCY

Frequency (Hz)

3. THEORY OF OPERATION

The following discussion refers to the Block Diagram. A FET current source is used to bias a 6.3 V zener diode.

The zener voltage is divided by the resistor network R1 and R2. This voltage is then applied to the noninverting

input of the operational amplier which amplies the voltage to produce a 5.0 V output. The gain is determined by

the resistor networks R3 and R4: G = 1 + R4/R3. The 6.3 V zener diode is used because it is the most stable diode

over time and temperature.

The current source provides a closely regulated zener current, which determines the slope of the references’ volt-

age vs. temperature function. By trimming the zener current a lower drift over temperature can be achieved. But

since the voltage vs. temperature function is nonlinear this compensation technique is not well suited for wide tem-

perature ranges.

A nonlinear compensation network of thermistors and resistors is used in the VRE series voltage references. This

proprietary network eliminates most of the nonlinearity in the voltage vs. temperature function. By adjusting the

slope, this device produces a very stable voltage over wide temperature ranges.

This network is less than 2% of the overall network resistance so it has a negligible effect on long term stability.

P r o d u c t I n n o v a t i o n F r o m

VRE505

4 VRE505DS

The proper connection of the VRE505 series voltage references with the optional trim resistor for initial error and

the optional capacitor for noise reduction is shown below. The VRE505 reference has the ground terminal brought

out on two pins (pin 4 and pin 7) which are connected together internally. This allows the user to achieve greater

accuracy when using a socket. Voltage references have a voltage drop across their power supply ground pin due to

quiescent current owing through the contact resistance. If the contact resistance was constant with time and tem-

perature, this voltage drop could be trimmed out. When the reference is plugged into a socket, this source of error

can be as high as 20 ppm. By connecting pin 4 to the power supply ground and pin 7 to a high impedance ground

point in the measurement circuit, the error due to the contact resistance can be eliminated. If the unit is soldered

into place, the contact resistance is sufciently small that it does not effect performance. Pay careful attention to the

circuit layout to avoid noise pickup and voltage drops in the lines.

EXTERNAL CONNECTIONS

VRE505

TOP

VIEW

N/C

+VIN

TEMP

GND

NOISE

REDUCTION

REF. GND

VOUT

TRIM

+ VOUT

+ VIN

VRE505

10KΩ

1µF

OPTIONAL

NOISE REDUCTION

CAPACITOR

OPTIONAL

FINE TRIM

ADJUSTMENT

VTEMP OUT

REF. GND

PIN CONFIGURATION

CONTACTING CIRRUS LOGIC SUPPORT

For all Apex Precision Power product questions and inquiries, call toll free 800-546-2739 in North America.

For inquiries via email, please contact tucson.support@cirrus.com.

International customers can also request support by contacting their local Cirrus Logic Sales Representative.

To nd the one nearest to you, go to www.cirrus.com

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