International Rectifier (IR, El Segundo, CA) recently announced its IR2171 Current Sensing IC for linear sensing of motor phase current in ac or bldc motor drive applications. According to IR, the 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 claimed to be better than 0.5 percent over the specified usable range. Circuit blocks in the IR2171 include differential amplifier, analog to digital converter, high voltage level shifter and pulse width modulation (PWM) encoded current sense signal feedback. Typical performance parameters include 0.4 percent linearity with 0.0003 percent temperature drift, 1.5mV total offset with 30uV/degree C drift, one percent gain error with 37ppp/degree C drift and power supply rejection ratio of 0.06 percent at 6kHz with 1Vpp power supply noise. The IR2171 is housed in a SOIC-8 or DIP-8 package. In quantities of 1,000, pricing for the device starts at $3.95 each. Samples are currently available and a 1200V version will be available in the first quarter 2000.