Apple Inc.
Digital sensor with embedded reference clock

Abstract:

A sensor circuit and integrated circuit having the same is disclosed. In one embodiment, a sensor circuit includes first and second ring oscillators having different circuit topologies. A first counter is coupled to receive an output signal from the first ring oscillator, while a second counter is coupled to receive an output signal from the second ring oscillator. The sensor circuit further includes a local clock circuit that provides a clock signal to the first and second counters. Furthermore, the local clock circuit is coupled to provide the clock signal exclusively to circuitry within the sensor circuit, the circuitry including the first and second counters.