REV. B

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a

1B22

FUNCTIONAL BLOCK DIAGRAM

IN2

4mA

OFFSET

RESISTOR

NETWORK

REF

IN1

S. NODE

RECTIFIER/

LOOP SUPPLY

SYNC

+15V

A. COM

–15V

P. COM

PROT

OUT

HI

OUT

LO

1B22

DEMODULATOR

MODULATOR

OSCILLATOR

SIGNAL

ISOLATION

POWER

ISOLATION

Programmable, Isolated

Voltage-to-Current Converter

FEATURES

Internal Isolated Loop Supply Drives 1000

Load

Pin Programmable Inputs: 0 V to +5 V or 0 V to +10 V

Pin Programmable Outputs: 4 to 20 mA or 0 to 20 mA

High CMV Isolation: 1500 V RMS

Normal-Mode Output Protection: 240 V RMS

High Accuracy

Low Offset Tempco:

300 nA/ C

Low Gain Tempco:

50 ppm/ C

Low Nonlinearity:

0.02%

High CMR: 90 dB min

Small Package: 1.0"

2.10"

0.35"

Meets IEEE STD 472: CMV Transient Protection (SWC)

APPLICATIONS

Multichannel Process Control

D/A Converter—Current Loop Interface

Analog Transmitters and Controllers

Remote Data Acquisition Systems

GENERAL DESCRIPTION

The 1B22 is an isolated voltage-to-current converter that

incorporates transformer isolation to achieve high performance

and automated surface mount manufacturing for low cost

and increased reliability. Designed for industrial applications,

it is especially suited for harsh environments with extremely

high common-mode interference. With programmable inputs

and outputs, the 1B22 provides an unbeatable combination of

versatility and performance in a compact plastic package.

Functionally, the V/I converter consists of four basic sections:

input conditioning, modulator/demodulator, isolated loop

supply and current source (Figure 1). The 1B22 is pin program-

mable for 0 V to +5 V or 0 V to +10 V inputs and 0 to 20 mA

or 4 to 20 mA outputs using an internal resistor network. It can

also be set by an external resistor to accept 0 V to +1 V to 0 V

to +10 V inputs. Transformer coupling provides 1500 V rms

galvanic isolation between the inputs and the current loop.

Nonlinearity is an excellent

±0.05% max.

Loop power is generated internally through a dc/dc converter

and is also isolated from the input side (1500 V rms). Loop

compliance voltage is dependent on the voltage supplied to the

Ω

load.

The 1B22 is fully specified over –25

°C to +85°C and operates

over the industrial (–40

°C to +85°C) temperature range.

DESIGN FEATURES AND USER BENEFITS

Isolated Loop Power: Internal loop supply completely

isolates the loop from the input terminals (1500 V rms) and

provides the capability to drive 0

Ω to 1000 Ω loads. This elimi-

nates the need for an external dc/dc converter.

Ease of Use: The 1B22 offers complete isolated voltage-to-

current conversion with minimum external parts required to get

a conditioned current signal. No external buffers or drivers are

required.

High CMV Isolation: The 1B22 features high input to output

galvanic isolation to eliminate ground loops and offer protection

against damage from transients and fault voltages. The isolation

barrier will withstand continuous CMV of 1500 V rms and meets

the IEEE Standard for Common-Mode Voltage Transient Pro-

tection (STD 472-SWC).

Small Size: The 1B22 package size (1.0"

× 2.1" DIP) makes it

an excellent choice in multichannel systems for maximum chan-

nel density. The 0.35" height also facilitates applications with

limited board clearance.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2000