Ultra-low-power power supply system for an IC chip

An IC chip, comprising:

• a power supply circuit, comprising:
• a power supply line for a power supply;
• a capacitive voltage divider having an input switch, an input capacitor, a plurality of switched capacitors and an output capacitor, the capacitive voltage divider to sample a voltage level of the power supply line by closing the input switch, and to generate a divided sampled voltage on the output capacitor by selectively connecting the switched capacitors;
• a comparator coupled to the output capacitor to compare the divided sampled voltage to a reference voltage;
• and
• a control circuit to control the capacitive voltage divider for closing the input switch and selecting the switched capacitors.

A method to control power supply for an IC chip, comprising:

• sample a voltage level on a power supply line on the IC chip;
• select one or more switched capacitors from a plurality of switched capacitors to generate a divided sampled voltage level;
• compare the divided sampled voltage level to a reference voltage;
• and
• determine the voltage level of the power supply line.