TOF range finding sensor in 90nm CMOS capable of suppressing 180 klx ambient light

In this work an integrated Time-Of-Flight (TOF) based range finding single pixel sensor in 90nm CMOS is presented. The sensor exploits a PN photodiode for the signal detection, achieving the pixel size of 80 × 86.5 μm² at the fill factor of ~93%. Measurement results show a standard deviation of 2.5 cm at 1 m and less than 8 cm for distances up to 3.2 m. Ambient light suppression is accomplished inherently in pixel through the bridge correlator circuit approach, whereby the measured distance changes only in the range +3.2cm to -1.2cm for applied DC light up to 180 klx. An inverter feedback ensures a long integration of the modulated signal canceling out the influence of the photodiode capacitance. Due to very small structure sizes, the circuit itself occupies an area of only 13 × 17 μm² and together with a shrunken photodiode high count multipixel sensors can be realized.