Description
The HCPL-7840 isolation amplifer 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 HCPL-7840. A differential output voltage is created on the other side of the HCPL-7840 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 HCPL-7840 was designed to ignore very high common mode transient slew rates (of at least 10 kV/μs).
The high CMR capability of the HCPL-7840 isolation amplifer provides the precision and stability needed to accurately monitor motor current in high noise motor control environ-ments, providing for smoother control (less “torque ripple”) in various types of motor control applications.

Features
● 15 kV/μs common-mode rejection at VCM = 1000 V
● Compact, auto-insertable standard 8-pin DIP package
● 0.00025 V/V/°C gain drift vs. temperature
● 0.3 mV input offset voltage
● 100 kHz bandwidth
● 0.004% nonlinearity
● Worldwide safety approval:
   UL 1577 (3750 Vrms/1 min.)
   and CSA, IEC/EN/DIN EN 60747-5-2
● Advanced Sigma-Delta (∑-Δ) A/D converter technology
● Fully differential circuit topology
● 0.8 μm CMOS IC technology

Applications
● 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