Design of 10MHz Isolated Current Sense Amplifier Based on FDDA and Frequency Modulation

A 10MHz high precision isolated current sense amplifier (ICSA) based on fully differential difference amplifier (FDDA) and frequency modulation is presented. The proposed ICSA generates high frequency pulse utilizing voltage controlled oscillator (VCO), modulated by sensed voltage. The frequency is stabilized by feedback loop consisted by frequency-to-voltage converter (FVC) and clamp amplifier. Then the modulated high frequency pulse is transmitted across the isolation barrier. The FDDA is employed to provide high sensing bandwidth while suppressing offset and noise. The proposed ICSA is implemented with $0.18 \mu \mathrm{m}$ BCD process and the bandwidth is high to 10 MHz with fixed gain of 4.