The A7800/HCPL-7800(A) isolation amplifier family was designed for current sensing in electronic motor drives. The A7800 detects the analogue voltage drop caused by motor currents flowing through an external resistor in a typical design. A differential output voltage is created on the other side of the A7800 optical isolation barrier. The motor current is proportional to the differential output voltage, which can be converted to a single-ended signal using an op-amp as shown in the proposed application circuit.

The A7800 was intended to tolerate very high common-mode transient slew rates (of at least 10 kV/s) since common mode voltage fluctuations of several hundred volts in tens of nanoseconds are frequent in modern switching inverter motor drives. The HCPL-7800(A) isolation amplifier's high CMR capability provides the precision and stability required to correctly monitor motor current in high-noise motor control situations, resulting in smoother control (less "torque ripple") in a variety of motor control applications. The product can also be utilized for general analogue signal isolation applications that require high accuracy, stability, linearity and a gain tolerance of 3% in noisy environments. Avago Technologies offers the A7800 for precision applications, with a part-to-part gain tolerance of 1%.

The HCPL-7800(A) features a fully differential circuit topology, sigma delta (Σ−∆) analog-to-digital converter technology, and chopper stabilized amplifiers. These features work together to provide unrivalled isolation mode noise rejection, as well as exceptional offset, gain accuracy and stability over time and temperature. This performance is supplied in a small, auto-insertable 8-pin DIP package that complies with international regulatory safety standards.

Features :-

•  Compact, Auto-Insertable Standard 8-pin DIP Package 
•  Gain Drift vs. Temperature: 0.00025 V/V/°C
•  Input offset voltage of 0.3 mV
•  Bandwidth of 100 kHz 
•  Input offset voltage of 0.3 mV
•  Worldwide Safety Approval: UL 1577 (3750 Vrms/1 min. and CSA, IEC/EN/DIN EN 60747-5-2
•  Advanced Sigma-Delta (Σ−∆) A/D Converter Technology
•  Fully Differential Circuit Topology

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

For more details, you can refer to A7800 Datasheet

SPECIFICATIONS