ACPL-C78A, ACPL-C780, ACPL-C784

Miniature Isolation Amplifiers

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.

NOTE: A 0.1

μF bypass capacitor must be connected between pins 1 and

4 and between pins 5 and 8.

Description

The ACPL-C78A/C780/C784 family of isolation ampli-

fiers 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 ACPL-C78A/C780/C784. A

differential output voltage is created on the other side of

the ACPL-C78A/C780/C784 optical isolation barrier. This

differential output voltage is proportional to the motor

current and can be converted to a single-ended signal

by using an op-amp as shown in the recommended ap-

plication circuit. Since common-mode voltage swings

of several hundred volts in tens of nanoseconds are

common in modern switching inverter motor drives, the

ACPL-C78A/C780/C784 is designed to ignore very high

common-mode transient slew rates (of at least 10 kV/

μs).

The high CMR capability of the ACPL-C78A/C780/C784

isolation amplifier provides the precision and stability

needed to accurately monitor motor current in high noise

motor control environments, providing for smoother

control (less “torque ripple”) in various types of motor

control applications.

The product can also be used for general analog signal

isolation applications requiring high accuracy, stability,

and linearity under similarly severe noise conditions. For

general applications, we recommend the ACPL-C780 (gain

tolerance of ±3%) and the ACPL-C784 (gain tolerance of

±5%). For precision applications AvagoTechnologies offers

the ACPL-C78A with part-to-part gain tolerance of ±1%.

The ACPL-C78A/C780/C784 utilizes sigma-delta (

∑-∆) an-

alog-to-digital converter technology, chopper stabilized

amplifiers, and a fully differential circuit topology.

Together, these features deliver unequaled isolation-

mode noise rejection, as well as excellent offset and gain

accuracy and stability over time and temperature. This

performance is delivered in a compact, auto-insertable,

Stretched SO-8 (SSO-8) package that meets worldwide

regulatory safety standards.

Features

• Compact, Auto-Insertable Stretched SO-8 Package

• 0.00025 V/V/°C Gain Drift vs. Temperature

• 0.3 mV Input Offset Voltage

• 100 kHz Bandwidth

• 0.004% Nonlinearity

• WorldwideSafetyApproval:UL1577(5000Vrms/1min.),

CSA and IEC/EN/DIN EN 60747-5-5

• Advanced Sigma-Delta (∑-∆) A/D Converter Technology

• Fully Differential Amplifier

Applications

• Motor Phase and Rail Current Sensing

• Inverter Current Sensing

• DC bus voltage sensing

• General Purpose Current Sensing and Monitoring

• General Purpose Analog Signal Isolation

Functional Diagram

1

2

3

4

8

7

6

5

GND1

GND2

+

-

+

-

SHIELD