May 27, 2014 - Analog Devices introduced AD7403 isolated sigma-delta modulator for precision current and voltage measurement in DC/AC power conversion applications. The AD7403 achieves an 81-dB signal-to-noise and distortion ratio (SINAD) (min) @ 78 KSPS over a -40C° to +125C° temperature range, which is 11 dB higher than previous 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 Key Features
- 5-MHz to 20-MHz external clock input rate
- 16 bits, no missing codes
- Typical offset drift: 1.5 μV/°C
- On-board digital isolator
- On-board reference
- True bipolar analog input range: ±320 mV
- High common-mode transient immunity: >25 kV/μs
The AD7403 modulator is well suited to work with other ADI products designed for motor control and power conversion systems, including the ADSP-CM40x mixed-signal control processor, ADuM6000 isolated, 5-kV, DC/DC converter and the ADP2441 36-V, 1-A synchronous step-down DC/DC regulator.