Integrated variable-output switching converter with dual-loop Δ-Σ modulation for adaptive wireless powering in implantable devices

An integrated switching DC-DC power converter is proposed to implement an adaptive wireless powering scheme in implantable biomedical devices. The proposed dual-loop Δ-Σ modulation, error correction and noise shaping techniques work jointly to improve the transient response, noise suppression and line regulation performances. An observation-based double-sampling (OBDS) sensor and a double-sampling half-clock (DSHC) 1-bit A/D converter are also introduced to further increase the signal processing speed without causing any extra cost. The converter was designed with a standard 130-nm CMOS process. The fully transistor-based HSPICE simulation results demonstrate a 2.8/2.2-μs up/down tracking time to a full-range reference voltage step change. A 7.95-mV/V line regulation is achieved, when the supply voltage varies from 1.1 V to 1.5 V. With a 1.2-V supply, the maximum efficiency of 95.5% is measured at 0.9-V output voltage and 90-mW load power, while the efficiency stays above 80% over the entire 170-mW load power range.