Design of Integrated Dual-Loop $\Delta$ –$\Sigma$ Modulated Switching Power Converter for Adaptive Wireless Powering in Biomedical Implants

This paper presents an integrated CMOS switching power converter that accommodates adaptive wireless powering scheme in biomedical implants. It employs the techniques of dual-loop error correction, observation-based oversampling, and Δ- Σ modulation to enhance transient response, line/load regulation, and noise suppression performance. By adopting a digital filter for proportional-derivative compensation, fully on-chip frequency compensation is achieved. In addition, a double sampling technique is introduced to improve the signal processing speed. The converter was designed and fabricated with a 130-nm CMOS process. The measurement results demonstrate 23.2/20.4-μs up-/down-tracking times to full-range reference voltage step changes. A 28.5-mV/V line regulation is achieved, when the supply voltage varies from 1.15 to 1.50 V. In addition, with a 1.20-V supply, the converter responds to a 10%-to-100% load current step change within 22.1 μs. A maximum efficiency of 95.5% is measured at 0.90-V output voltage and 45-mW output power. Noise power spectrum demonstrates a 100-dB signal-to-noise ratio in the converter.