QCPL-7847-000E

The QCPL-7847 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 QCPL-7847. A differential output voltage is created on the other side of the QCPL-7847 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 QCPL-7847 was designed to ignore very high commonmode transient slew rates (of at least 10 kV/μs). The high CMR capability of the QCPL-7847 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, the QCPL-7847 (gain tolerance of ± 5%) is recommended. The QCPL-7847 utilizes sigma delta (Σ - ∆) analog-to-digital converter technology, chopper stabilized amplifiers, and a fully differential circuit topology fabricated using Avago’s 0.8 μm CMOS IC process. Together, these features deliver unequaled isolationmode 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, industry standard 8-pin DIP package that meets worldwide regulatory safety standards. (A gull-wing surface mount option is also available).

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

Key features

• Optical Isolation Barrier
• 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
• Safety approval: UL 1577 (3750 Vrms/1 min.), CSA and IEC/EN/DIN EN 60747-5-5 (pending)
• Advanced Sigma-Delta (∑ - ∆) A/D converter technology
• Fully differential circuit topology
• 0.8 μm CMOS IC technology