A supply voltage level detection circuit makes use of an additional supply already provided for power. A voltage detection circuit defines a first threshold, and a differencing circuit defines a second threshold. The output state of the differencing circuit is saved in a latch. The latch may be cross coupled gates of cross coupled inverters. When inverters are used, the differencing circuit output contends with the internal latch drive when setting or resetting the latch. The design allows the differencing circuit to overcome the inverter's internal drives to change the logic state of the latch.