Avago ACPL-C78A绝缘放大器方案

Avago公司的 ACPL-C78A/C780/C784是全差分绝缘放大器, 在VCM = 1000 V时的共模抑制为15 kV/µs,0.3mV的失调电压,设计用于马达相电流检测,逆变器电流检测,开关电源信号隔离以及通用的电流检测和监视与模拟信号隔离.本文介绍了ACPL-C78A的主要特性以及相关的测试电路如输入失调电压测试电路, 增益和非线性测试电路, 传输时延测试电路和应用电路.

The ACPL-C78A/C780/C784 isolation amplifier family was 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 application 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 was designed to ignore very high common-mode transient slew rates (of at least 10 kV/µs), which provides the precision and stability in high noise motor control environments.

The product can also be used for general analog signal isolation applications requiring high accuracy, stability, and linearity under similarly severe noise conditions. They are offered with gain tolerance of ±1% (ACPL-C78A), ±3% (ACPL-C780) and ±5% (ACPL-C784) to suit application need. The ACPL-C78A/C780/C784 utilizes sigma-delta analog-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 (with 30% smaller footprint compared to the DIP-8 package) that meets 8 mm clearance and creepage requirements and worldwide regulatory safety standards.

ACPL-C78A 主要特性:
15 kV/µs Common-Mode Rejection at VCM = 1000 V
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
Safety Approval (pending):  
UL 1577 (5000 Vrms/1 min.)
CSA
IEC/EN/DIN EN 60747-5-2
Advanced Sigma-Delta A/D Converter Technology
Fully Differential Amplifier
Options available are :
000E: Lead Free Option
060E: IEC/EN/DIN EN 60747-5-2 Option
500E: Tape and Reel Packaging Option
ACPL-C78A 应用:
Motor Phase and Rail Current Sensing
Inverter Current Sensing
Switched Mode Power Supply Signal Isolation
General Purpose Current Sensing and Monitoring
General Purpose Analog Signal Isolation



图1.ACPL-C78A输入失调电压测试电路



图2.ACPL-C78A增益和非线性测试电路



图3.ACPL-C78A传输时延测试电路




图4.ACPL-C78A CMIT测试电路



图5.ACPL-C78A应用电路