Continuous-wave time-of-flight CMOS detector with common-mode feedback for strong background light applications

A novel CMOS demodulation detector for time-offlight applications is presented. It can handle large amounts of background light by removing the resulting common-mode signal at the detector level. A common-mode feedback circuit is used on top of a current-assisted photonic demodulator (CAPD) to remove the incoming light that is not correlated to the modulation signal. A dynamic element matching (DEM) scheme is implemented to remove mismatches in the compensating current sources that operate at nanoampere currents. The detector is fabricated in a 0.35 μm process and is used to measure the phase of a 1 MHz square-wave modulated laser signal on top of a background light, more than 100 times more powerful, without the use of optical filters. Measurements are performed with and without DEM, demonstrating its need. The detector is a candidate for long range outdoor time-of-flight applications where background light can become multiple orders of magnitude larger than the modulated light.