250-mV Supply Subthreshold CMOS Voltage Reference Using a Low-Voltage Comparator and a Charge-Pump Circuit

This brief proposes a subthreshold CMOS voltage reference circuit, which reduces the minimum supply voltage by replacing the analog amplifier in the conventional CMOS voltage reference circuit with a low-voltage comparator, a charge-pump circuit, and a digital control circuit. The subthreshold CMOS voltage reference circuit was fabricated using a 0.11-μm CMOS process. Its core area was 0.013 mm2and it consumed 5.35 μW at VDD= 250 mV and fCLK= 1 MHz. Its minimum supply voltage was 242 mV. Ten sample chips generated 193-207-mV reference voltage with 0.4-3.2-mV/100-mV line sensitivity at VDD= 250-400 mV and 58-186 ppm/°C temperature coefficient at 10 °C-90 °C.