Embodiments of the present invention may provide a power supply system that uses a capacitive voltage divider to selectively monitor various power supplies on an IC chip. The power supply system may sample a monitored power supply to a capacitor and select certain capacitors from a set of switched capacitors to divide down the sampled voltage. The resulting voltage may be compared to a voltage reference. Using different selections of switched capacitors, the monitored power supply may be compared for different voltage levels. The ratio of the sampling capacitor to the selected capacitors may determine a voltage level the comparator will trigger. Further, based on the monitored power supply level, the power supply system may turn on a switch between an external power supply and a regulated digital power supply to charge the regulated digital power supply while a main LDO is turned off.