Analog Devices, Inc. has introduced the industry’s highest accuracy isolated sigma-delta modulator for precision current and voltage measurement in dc-ac power conversion applications. The AD7403 isolated sigma-delta modulator achieves an 81-dB signal-to-noise and distortion ratio (SINAD) (min) at 78 KSPS over a -40 to +125 degrees C temperature range, which is 11 dB higher than competing devices. The higher SINAD enables more accurate current and voltage measurement which improves the performance of motor drives by reducing torque ripple on the motor shaft. The higher SINAD also increases the power transfer efficiency in dc-ac power inverter applications, such as motor drives, solar and wind inverters.
The AD7403 isolated sigma-delta modulator integrates ADI’s iCoupler® digital isolation technology, creating a single-chip solution for measuring the voltage across a shunt resistor by converting an analog signal into a 1-bit data stream that can be clocked at up to 20 MHz. The increased isolation working voltage (1250 V peak) allows designers to replace less accurate, more costly Hall Effect sensors in higher dc-bus voltage power conversion and motor drive applications. The higher performance of the isolated sigma-delta modulator enables the use of a smaller shunt resistor, which reduces thermal loss across the shunt while retaining measurement accuracy.
AD7403 Isolated Sigma-Delta Modulator features include: 5-MHz to 20-MHz external clock input rate, 16 bits, no missing codes, Typical offset drift: 1.5 Î¼V/degree C, On-board digital isolator, On-board reference, True bipolar analog input range: ±320 mV, and High common-mode transient immunity: > 25 kV/ . In lots of 10,000 pieces, the AD7403 costs $2.95.It is available for immediate delivery and is packaged in a 16-lead, wide body SOIC (8.3mm creepage and clearance).