ACPL-796J

Optically Isolated Sigma-Delta Modulator

Data Sheet

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.

Description

The ACPL-796J is a 1-bit, second-order sigma-delta (

6')

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

x 5 MHz to 20 MHz external clock input range

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

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

x 74 dB minimum SNR

x 3.5 PV/°C maximum offset drift

x ±1% maximum gain error

x Internal reference voltage

x ±200 mV linear range with single 5 V supply

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

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

x SO-16 package

x 25 kV/Ps common-mode transient immunity

x Safety and regulatory approval (pending):

IEC/EN/DIN EN 60747-5-5: 1230 Vpeak working

insulation voltage

UL 1577: 5000 Vrms/1min double protection rating

CSA: Component Acceptance Notice #5

Applications

x Motor phase and rail current sensing

x Power inverter current and voltage sensing

x Industrial process control

x Data acquisition systems

x General purpose current and voltage sensing

x Traditional current transducer replacements

Functional Block Diagram

Figure 1.

Σ−Δ

MODULATOR/

ENCODER

SHIELD

LED

DRIVER

CLOCK

DETECTOR

SHIELD

DECODER

LED

DRIVER

MCLKIN

MDAT

GND2

GND1

ACPL-796J

+

−