The document describes a fully isolated current sensing circuit with built-in isolated power supply. The circuit features robustness and accurate measurement.
The CN-0280 is a fully isolated current sensing circuit engineered and tested for quick system integration in analog, mixed-signal, and RF design challenges. It is specifically designed for use in solar photovoltaic (PV) inverter systems, providing accurate current measurement in high-voltage environments where peak AC voltages can reach hundreds of volts and currents vary from a few mA to 25 A.
The circuit utilizes a 1 mΩ sense resistor and a dual-channel AD8639 low-offset amplifier to measure peak currents up to ±25 A. The signal is processed by an AD7401A isolated Σ-Δ modulator, which outputs a single-stream 16 MHz bit stream suitable for processing by a DSP via a sinc3 digital filter. The design includes protection against transient overvoltage and ESD, and features a single-pole RC filter to reduce bandwidth noise.