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ACPL-796J

Optically Isolated Sigma-Delta Modulator

Avago Technologies 

ACPL-796J

Optically Isolated Sigma-Delta Modulator

Data Sheet

Description

The ACPL-796J is a 1-bit, second-order sigma-delta ()

modulator converts an analog input signal into a high-

speed data stream with galvanic isolation based on optical

coupling technology. The ACPL-796J operates from a 5 V

power supply with dynamic range of 80 dB with an appro-

priate digital filter. The differential inputs of ±200 mV (full

scale ±320 mV) are ideal for direct connection to shunt

resistors or other low-level signal sources in applications

such as motor phase current measurement.

The analog input is continuously sampled by means of

sigma-delta over-sampling using external clock, coupled

across the isolation barrier, which allows synchronous

operation with any digital controller. The signal infor-

mation is contained in the modulator data, as a density

of ones with data rate up to 20 MHz, and the data are

encoded and transmitted across the isolation boundary

where they are recovered and decoded into high-speed

data stream of digital ones and zeros. The original signal

information can be reconstructed with a digital filter. The

serial interface has a wide supply range of 3 V to 5.5 V.

Combined with superior optical coupling technology,

the modulator delivers high noise margins and excellent

immunity against isolation-mode transients. With 0.5 mm

minimum distance through insulation (DTI), the ACPL-796J

provides reliable double protection and high working

insulation voltage, which is suitable for fail-safe designs.

This outstanding isolation performance is superior to

alternatives including devices based on capacitive- or

magnetic-coupling with DTI in micro-meter range. Offered

in an SO-16 package, the isolated ADC delivers the reli-

ability, small size, superior isolation and over-temperature

performance motor drive designers need to accurately

measure current at much lower price compared to tradi-

tional current transducers.

The internal clock version modulators, HCPL-7860 (DIP-8/

gull wing surface mount package) and HCPL-786J (SO-16

package), are also available.

Features

 5 MHz to 20 MHz external clock input range

 1-bit, second-order sigma-delta modulator

 16 bits resolution no missing codes (12 bits ENOB)

 74 dB minimum SNR

 3.5 V/°C maximum offset drift

 ±1% maximum gain error

 Internal reference voltage

 ±200 mV linear range with single 5 V supply

 3 V to 5.5 V wide supply range for digital interface

 –40°C to +105°C operating temperature range

 SO-16 package

 25 kV/s common-mode transient immunity

 Safety and regulatory approval:

IEC/EN/DIN EN 60747-5-5: 1414 Vpeak working

insulation voltage

UL 1577: 5000 Vrms/1min double protection rating

CSA: Component Acceptance Notice #5

Applications

 Motor phase and rail current sensing

 Power inverter current and voltage sensing

 Industrial process control

 Data acquisition systems

 General purpose current and voltage sensing

 Traditional current transducer replacements

Functional Block Diagram

VDD1

VIN +

Σ−Δ

LED

MODULATOR/ DRIVER

DECODER

VIN −

ENCODER

SHIELD

VDD2

MDAT

VREF

GND1

CLOCK

DETECTOR

SHIELD

LED

DRIVER

ACPL-796J

MCLKIN

GND2

Figure 1.

CAUTION: It is advised that normal static precautions be taken in handling and assembly of this

component to prevent damage and/or degradation which may be induced by ESD. The components

featured in this datasheet are not to be used in military or aerospace applications or environments.

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