HCPL-788J Integarted Circuts Chip IC Electronics ICs Chip

Isolation Amplifier with Short Circuit and Overload Detection

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Feature

 • Output Voltage Directly Compatible with A/D Converters (0 V to VREF)

• Fast (3 µs) Short Circuit Detection with Transient Fault Rejection

• Absolute Value Signal Output for Overload Detection

• 1 µV/°C Offset Change vs. Temperature

• SO-16 Package

• -40°C to +85°C Operating Temperature Range

• 25 kV/µs Isolation Transient Immunity

• Regulatory Approvals (Pending): UL, CSA, VDE 0884 (891 Vpeak Working Voltage)

Description

The HCPL-788J isolation amplifier is designed for current sensing in electronic motor drives. In a typical implementation, motor currents flow through an external resistor and the resulting analog voltage drop is sensed by the HCPL-788J. A larger analog output voltage is created on the other side of the HCPL-788J’s optical isolation barrier. The output voltage is proportional to the motor current and can be connected directly to a singlesupply A/D converter. A digital over-range output (FAULT) and an analog rectified output (ABSVAL) are also provided. The wire OR-able over-range output (FAULT) is useful for quick detection of short circuit conFigure 1. Current Sensing Circuit. ditions on any of the motor phases. The wire-OR-able rectified output (ABSVAL), simplifies measurement of motor load since it performs polyphase rectification. Since the common-mode voltage swings several hundred volts in tens of nanoseconds in modern electronic motor drives, the HCPL-788J was designed to ignore very high common-mode transient slew rates (10 kV/µs).