The linear sensing of motor phase current in AC or BLDC motor drive applications is the forte of IR2171 IC. This 600V device integrates all motor phase current measurement, analog-to-digital conversion, noise filtering and feedback interfacing to a microcontroller in a single chip. The current measurement linearity is better than 0.5% over the specified usable range. Important performance parameters include 0.4% linearity with 0.0003% temperature drift, 1.5 mV total offset with 30 µV/°C drift, 1% gain error with 37 ppm/°C drift, and power supply rejection ratio of 0.06% at 6 kHz with 1 Vpp power supply noise. A current loop with better than 2 kHz usable bandwidth can easily be constructed using the IR2171 at the heart of the control loop. The 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.