Successive-divider-line ADC dedicated to low-power medical devices

A low-power and small silicon area digitally controlled Switched Mode Power Supply (SMPS) is intended for the minimization of both power and size of an on-chip DC power supply building block which is mainly dedicated for implantable medical sensing and microstimulation devices. Such SMPS is based on a successive divider-line analog-to-digital Converter (SDLADC), which is the focus of this paper. Special attention is paid for reducing the power consumption and silicon area of this SDLADC, which consists of a resistor network based on diode connected transistor used to replace the delay-line of the windowed ADC. To compensate process and temperature variations, a digital calibration technique is used to meet the specified static and dynamic output voltage regulations and avoid variations of the regulated SMPS output voltage. The proposed ADC is implemented in AMS 0.35 μm CMOS process. Simulation results show a current consumption of 1.5 μA/MHz and conversion time of 10 ns much lower than recent conventional topology values. The proposed circuit exhibits a quantization steps smaller than 1.6% of Vref and it can be a solution for high switching frequency, which results on faster regulation of SMPS output voltage.