EL SEGUNDO, CA. November 1999 - International Rectifier (IR^®:), the power conversion expert, now offers its IR2171 Current Sensing IC solution for linear sensing of motor phase current in AC or BLDC motor drive applications. The new 600V device integrates all motor phase current measurement, analog to digital conversion, noise filtering and feedback interface to micro-controller in a single chip. Current measurement linearity is better than 0.5% over the specified usable range.

"Precision measurement of motor phase current has been a challenge because of the small differential mode signal that rides on top of the large common mode swinging voltage driving the motor phase," said David Tam, Vice President for Power Integrated Circuit Products at IR. "Older designs employ Hall-effect sensors that are bulky and expensive, while newer alternatives use the linear opto-couplers that require complex multi-chip construction and many external supporting circuits. And both these alternatives require expensive isolated power supplies.

"Now engineers can specify the single chip IR2171 to handle the task," he claimed. "This new device interfaces directly to a micro-controller using a PWM output and runs off a bootstrap supply to greatly reduce size requirements and cost."

Circuit blocks in the 600V IR2171 include precision differential amplifier, analog to digital converter, high voltage level shifter and PWM encoded current sense signal feedback. Important performance parameters typically include 0.4% linearity with 0.0003% temperature drift, 1.5mV total offset with 30mV/°C drift, 1% gain error with 37ppm/°C drift and power supply rejection ratio of 0.06% at 6kHz with 1Vpp power supply noise. A current loop with better than 2kHz usable bandwidth can easily be constructed using the IR2171 at the heart of the control loop.

The IR2171 is the newest member in the chip-set family supporting the IR Power Conversion Processor Architecture. New chips in the family include gate driver with IGBT protection (IR2137), soft starting controller for the input converter (IR1110), and now the linear current sensing IC (IR2171). The complete chip-set evolves the IR architecture from open-loop V/Hz control to provide cost-effective power conversion platforms for sensor-less vector or servo control.

The 600V IR2171 is housed in a SOIC-8 or DIP-8 package, with prices starting at $3.95 each in quantities of 1,000. Samples are now available with production starting in November. A 1200V version will be available in Q1 2000.