Isolated Sigma-Delta Modulator Boost Motor-Driver, Power-Inverter Efficiency

According to Analog Devices (ADI), its AD7403 isolated sigma-delta modulator delivers the highest accuracy for current and voltage measurement in dc-ac power-conversion applications. It achieves an 81-dB signal-to-noise and distortion ratio (SINAD) (min) at 78 ksamples/s over a ‒40 to +125°C temperature range—11 dB higher than competing devices, says the company. The boost in SINAD helps improve motor-drive performance by reducing torque ripple on the motor shaft, as well as increases power-transfer efficiency in dc-ac power-inverter applications. The device integrates ADI’s iCoupler digital isolation technology, which creates a single-chip solution for measuring voltage across a shunt resistor by converting an analog signal into a 1-bit data stream that’s clockable up to 20 MHz. With increased isolation working voltage (1250 V peak), designers can replace more costly Hall-effect sensors in higher dc-bus voltage power-conversion and motor-drive apps. Typical offset drift is 1.5 µV/°C, and true bipolar input range is ±320 mV. The AD7403 comes in 16-lead, wide-body SOIC packaging with 8.3-mm creepage and clearance.

ANALOG DEVICES INC.