DC1748A-B - LINEAR TECHNOLOGY

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DEMO MANUAL DC1748A

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VCC Input Supply Range LTM2883-5 4.5 5 5.5 V

LTM2883-3 3.0 3 3.6 V

VCC2 Regulated Output Voltage 4.75 5 5.25 V

Adjustable Output Voltage Range 3.0 5.5 V

Maximum Load Current 20 mA

V+Regulated Output Voltage 12 12.5 13 V

Adjustable Output Voltage Range 1.22 14 V

Maximum Load Current 20 mA

V–Regulated Output Voltage –12 –12.5 –13 V

Adjustable Output Voltage Range –1.22 14 V

Maximum Load Current 15 mA

fMAX Maximum Data Rate DI1 → O1, Ix → DOx, CL = 10pF 10 MHz

LTM2883-S, Bidirectional Communication

LTM2883-S, Unidirectional Communication

MHz

LTM2883-I 400 kHz

VIORM Maximum Working Insulation Voltage GND to GND2 560

400

VDC

VRMS

Common Mode Transient Immunity 30 kV/µs

DESCRIPTION

LTM2883 SPI/Digital or

I2C µModule Isolator with Adjustable ±12.5V

and 5V Regulated Power

Demonstration circuit 1748A is a serial peripheral interface

bus (SPI) or inter-IC bus (I2C) SPI/digital or I2C µModule

isolator with adjustable ±12.5V and 5V regulated power

featuring the LTM2883. The demo circuit features an EMI

optimized circuit conﬁ guration and printed circuit board

layout. All components are integrated into the µModule

isolator. The demo circuit operates from a single external

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

PERFORMANCE SUMMARY

(TA = 25°C)

supply on VCC. The part generates output voltages on VCC2,

V+, and V–, which may be adjusted by external program-

ming resistors. It communicates all necessary signaling

across the isolation barrier through LTC’s isolator µModule

technology.

Design ﬁ les for this circuit board are available at

http://www.linear.com/demo

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DEMO MANUAL DC1748A

OPERATING PRINCIPLES

The LTM2883 contains an isolated DC/DC conversion

system, including a boost converter and inverting charge

pump, with multiple LDO’s to deliver power to the three

output voltage rails from VCC. Isolation is maintained by

the separation of GND and GND2 where signiﬁ cant operat-

ing voltages and transients can exist without affecting the

operation of the LTM2883. The logic side ON pin enables

or shuts down the LTM2883. All logic side signals are

referenced to the logic supply pin VL. The LTM2883 is

available in two data bus conﬁ gurations, SPI (-S) or I2C

(-I), and with two input voltage ranges, 3.0 to 3.6 volts

(-3) or 4.5 to 5.5 volts (-5).

SPI signaling is controlled by the logic inputs CS, SDI,

and SCK. SDOE controls the SDO output and is normally

connected to CS. The corresponding Isolated side output

signals are CS2, SDI2, and SCK2. SDO2 is the isolated

side SPI data input. All of the SPI communication channels

may be used as generic digital I/O.

I2C signaling is controlled by the logic inputs SDA and

SCL, corresponding to SDA2 and SCL2 on the isolated

side. The SCL channel is unidirectional supporting master

mode only I2C communication. SCL2 output is standard

CMOS push-pull drive. SDA signaling is bidirectional,

and includes an internal current source pull-up on SDA2

supporting up to 200pF of load capacitance.

Demo circuit 1748A is available in four conﬁ gurations

supporting all versions of the LTM2883. Table 2 details

the demo circuit conﬁ gurations.

Table 2.

DEMO CIRCUIT INPUT VOLTAGE COMMUNICATION

DC1748A-A 3.0V to 3.6V SPI/Digital

DC1748A-B 4.5V to 5.5V SPI/Digital

DC1748A-C 3.0V to 3.6V I2C

DC1748A-D 4.5V to 5.5V I2C

The demo circuit has been designed and optimized for low

RF emissions. To this end some features of the LTM2883

are not available for evaluation on the demo circuit. The

logic supply voltage VL is tied to VCC on the demo circuit,

and the ON pin is not available on the input pin header,

but may be controlled by jumper JP1. EMI mitigation

techniques used include the following.

1. Four layer PCB, allowing for isolated side to logic side

bridge capacitor. The bridge capacitor is formed be-

tween an inner layer of ﬂ oating copper which overlaps

the logic side and isolated side ground planes. This

structure creates two series capacitors, each with

approximately .008" of insulation, supporting the full

dielectric withstand rating of 2500VRMS. The bridge

capacitor provides a low impedance return path for

injected currents due to parasitic capacitances of the

LTM2883’s signal and power isolating elements.

2. Discrete bridge capacitors (C3, C4) mounted between

GND2 and GND. The discrete capacitors provide ad-

ditional attenuation at frequencies below 400MHz.

Capacitors are safety rated type Y2, manufactured by

Murata, part number GA342QR7GF471KW01L.

3. Board/ground plane size has been minimized. This

reduces the dipole antenna formed between the logic

side and isolated side ground planes.

4. Top signal routing and ground ﬂ oods have been opti-

mized to reduce signal loops, minimizing differential

mode radiation.

5. Common mode ﬁ ltering is integrated into the input and

output pin headers. Filtering helps to reduce emissions

caused by conducted noise and minimizes the effects

of cabling to common mode emissions.

6. A combination of low ESL and high ESR decoupling is

used. A low ESL ceramic capacitor is located close to

the module minimizing high frequency noise conduction.

A high ESR tantalum capacitor is included to minimize

board resonances and prevent voltage spikes due to

hot plugging of the supply voltage.

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DEMO MANUAL DC1748A

OPERATING PRINCIPLES

Figure 1. DC1748 Radiated Emissions

EMI performance is shown in Figure 1, measured using

a Gigahertz Transverse Electromagnetic (GTEM) cell and

method detailed in IEC 61000-4-20, “Testing and Mea-

surement Techniques – Emission and Immunity Testing

in Transverse Electromagnetic Waveguides”.

The demo circuit includes provisions for programming

the three output voltage rails. Resistors R5, R6, and R7

allow the V+, V–, and VCC2 power rails, respectively, to

be reduced from their nominal operating voltages. The

formulas presented in Table 3 allow selection of the ap-

propriate resistor values.

Table 3.

VOLTAGE RAIL RESISTOR TO REDUCE OUTPUT

V+R5 = 150k • (V+ – 1.22)/(12.5 – V+)

V–R6 = 150k • (1.22 + V–)/(–12.5 – V–)

VCC2 R7 = 110k • (VCC2 – 0.6)/(5 – VCC2)

FREQUENCY (MHz)

–30

dBµV/m

–20

600 700 800 900

DC1748A F01

–10

100 200 300 400 500 1000

DETECTOR = QuasiPeak

RBW = 120kHz

VBW = 300kHz

SWEEP TIME = 17s

# OF POINTS = 501

DC1748A-A

DC1748A-B

CISPR 22 CLASS B LIMIT

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DEMO MANUAL DC1748A

Demonstration circuit 1748A is easy to set up and evalu-

ate the performance of the LTM2883. Refer to Figure 2

for proper measurement equipment setup and follow the

procedure below.

NOTE: When measuring the input or output voltage ripple

or high speed signals, care must be taken to avoid a long

ground lead on the oscilloscope probe.

1. Install JP1 in the ON (default) position.

2. With power off, connect the input power supply to VCC

and GND on pin header J1.

QUICK START PROCEDURE

3. Turn on the power at the input.

NOTE: Make sure that the input voltage does not

exceed 6V.

4. Check for the proper output voltages. VCC2 = 5V,

V+ = 12.5V, and V– = –12.5V on pin header J2.

5. Once the proper output voltages are established, con-

nect signals to J1 and J2 pin headers as appropriate.

The header pin names and locations are detailed on the

demo board silkscreen below the pin headers.

Figure 2. Demo Board Setup

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DEMO MANUAL DC1748A

Layer 1. Top Layer

PCB LAYOUT

Layer 2. Ground Plane

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DEMO MANUAL DC1748A

Layer 3. Signal Layer

PCB LAYOUT

Layer 4. Bottom Layer

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DEMO MANUAL DC1748A

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 1 U1-A IC, LTM2883CY-3S Linear Technology LTM2883CY-3S#PBF

1 U1-B IC, LTM2883CY-5S Linear Technology LTM2883CY-5S#PBF

1 U1-C IC, LTM2883CY-3I Linear Technology LTM2883CY-3I#PBF

1 U1-D IC, LTM2883CY-5I Linear Technology LTM2883CY-5I#PBF

Hardware/Components (For Demo Board Only)

2 1 C1 Capacitor, Tantalum 10F 10V 20% TAJA AVX TAJA106M010RNJ

3 1 C2 Capacitor, Ceramic 1F 10V 20% 0508 Murata LLL219R71A105MA01L

4 2 C3, C4 Capacitor, Ceramic 470pF 250VAC 10% 1808 Murata GA342QR7GF471KW01L

5 2 J1, J2 0.1" Double Row Header, 5 × 2 Pin Samtec TSW-105-22-G-D

6 2 J1, J2 0.1" Ferrite Plate, 5 × 2 Hole Fair Rite 2644247101

7 1 J2 Connection, Filtered, DSUB 9-Pin Kobiconn 152-3609

8 1 JP1 2mm Single Row Header, 3-Pin Samtec TMM-103-02-L-S

9 1 JP1 Shunt Samtec 2SN-BK-G

10 1 R1-C Resistor, Chip 10k 1% 0805 Yageo RC0805FR-0710KL

1 R1-D Resistor, Chip 10k 1% 0805 Yageo RC0805FR-0710KL

11 1 R2-C Resistor, Chip 10k 1% 0805 Yageo RC0805FR-0710KL

1 R2-D Resistor, Chip 10k 1% 0805 Yageo RC0805FR-0710KL

12 1 R3-C Resistor, Chip 0 0805 Yageo RC0805FR-070RL

1 R3-D Resistor, Chip 0 0805 Yageo RC0805FR-070RL

13 1 R4-A Resistor, Chip 0 0805 Yageo RC0805FR-070RL

1 R4-B Resistor, Chip 0 0805 Yageo RC0805FR-070RL

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DEMO MANUAL DC1748A

SCHEMATIC DIAGRAM

(DC1748A-A/DC1748A-B)

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DEMO MANUAL DC1748A

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation

that the interconnection of its circuits as described herein will not infringe on existing patent rights.

SCHEMATIC DIAGRAM

(DC1748A-C/DC1748A-D)

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DEMO MANUAL DC1748A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

LT 1210 • PRINTED IN USA

DEMONSTRATION BOARD IMPORTANT NOTICE

Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:

This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT

OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete

in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety

measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union direc-

tive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.

If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date

of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU

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arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all

appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or

agency certified (FCC, UL, CE, etc.).

No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,

customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.

LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.

Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and

observe good laboratory practice standards. Common sense is encouraged.

This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC applica-

tion engineer.

Mailing Address:

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1630 McCarthy Blvd.

Milpitas, CA 95035