ACPL-798J

Optically Isolated Sigma-Delta Modulator with LVDS Interface

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-798J is a 1-bit, second-order sigma-delta (

Σ-∆)

modulator that oversamples an analog input signal into

a highspeed data stream with galvanic isolation based

on optical coupling technology. The ACPL-798J operates

from a 5 V power supply with dynamic range of 82 dB with

an appropriate 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 applica-

tions 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 25 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

ACPL-798J comes with an LVDS interface on both clock

inputs and data outputs for better signal integrity.

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-798J

provides reliable double protection and high working in-

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

This outstanding isolation performance is superior to al-

ternatives including devices based on capacitive or mag-

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

an SO-16 package, the isolated ADC delivers the reliability,

small size, superior isolation and over-temperature perfor-

mance motor drive designers need to accurately measure

current at much lower price compared to traditional

current transducers.

Features

• Up to 25 MHz external clock input range

• LVDS clock and data interface.

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

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

• 75dB Typical SNDR

• 3.5mV/°C maximum offset drift

• ±1% maximum gain error

• ±200 mV linear range with single 5 V supply

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

• SO-16 package

• 25 kV/ms common-mode transient immunity

• Safety and regulatory approval (pending):

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 replacement

Functional Block Diagram

Figure 1.

Lead (Pb) Free

RoHS 6 fully

compliant

RoHS 6 fully compliant options available;

-xxxE denotes a lead-free product

SHIELD

VREF

LED

DRIVER

CLOCK

DETECTOR

DECODER

LED

DRIVER

MCLKIN+

MDAT-

VDD2

GND2

GND1

ACPL-798J

SHIELD

MCLKIN-

MDAT+

Σ−∆

MODULATOR/

ENCODER