May 29, 2014 – Analog Devices ( www.analog.com , NASDAQ: ADI), a global leader in high-performance semiconductors for signal processing applications, announced an isolated sigma-delta modulator for precision current and voltage measurements in DC/AC power conversion applications, featuring industry-leading accuracy. The AD7403 isolated sigma-delta modulator achieves a signal-to-noise and distortion ratio (SINAD) of at least 81 dB over a temperature range of -40°C to +125°C at 78 KSPS, which is 11 dB higher than competing products. Higher SINAD results in more accurate power and voltage measurements, reducing torque ripple on motor shafts and improving motor drive performance. Additionally, it enhances power transfer efficiency in DC/AC power inverter applications, such as motor drives and inverters for solar and wind power generation.

The AD7403 isolated sigma-delta modulator is integrated with ADI’s iCoupler® digital isolation technology to convert analog signals into a 1-bit data signal stream with a clock speed of up to 20 MHz, enabling the creation of a single-chip solution for voltage measurement passing through a shunt resistor. With increased isolated operating voltage (1250 V peak), designers can avoid using low-accuracy and high-cost Hall effect sensors in power conversion and motor drive applications involving relatively high DC bus voltages.

When the performance of the isolation sigma-delta modulator is improved, the size of the shunt resistor used is reduced, which consequently maintains measurement accuracy while also reducing heat loss during passage through the shunt.

The main functions of the AD7403 isolated sigma-delta modulator are as follows.
• 5MHz ~ 20MHz external clock input rate
• 16-bit, no code loss
• Offset drift (Typ): 1.5μV/°C
• On-board digital isolator
• On-board reference
• Bipolar analog input range: ±320mV
• High common-mode transient immunity: >25kV/μs

The AD7403 modulator is suitable for use with other ADI products designed for motor control and power conversion systems, such as the ADSP-CM40x mixed-signal control processor, ADuM6000 5kV isolated DC/DC converter, and ADP2441 36V 1A synchronous step-down DC/DC regulator.