US 11,796,386 B2
Optical sensor and apparatus comprising an optical sensor having a readout circuit to determine an ambient light level based on voltage across a photodetector at the end of an exposure time
Jeffrey M. Raynor, Edinburgh (GB); Sophie Taupin, Saint Egreve (FR); Jean-Jacques Rouger, Saint Pierre de Mesage (FR); and Pascal Mellot, Lans en Vercors (FR)
Assigned to STMicroelectronics (Research & Development) Limited, Marlow (GB); and STMicroelectronics (Grenoble 2) SAS, Grenoble (FR)
Filed by STMicroelectronics (Research and Development) Limited, Marlow (GB); and STMicroelectronics (Grenoble 2) SAS, Grenoble (FR)
Filed on Jun. 29, 2021, as Appl. No. 17/362,548.
Application 17/362,548 is a continuation of application No. 16/740,676, filed on Jan. 13, 2020, granted, now 11,079,270.
Claims priority of application No. 19305052 (EP), filed on Jan. 16, 2019.
Prior Publication US 2021/0325243 A1, Oct. 21, 2021
This patent is subject to a terminal disclaimer.
Int. Cl. G01J 1/42 (2006.01); G01J 1/44 (2006.01); H01L 23/58 (2006.01); H01L 27/144 (2006.01); H01L 31/02 (2006.01)
CPC G01J 1/4204 (2013.01) [G01J 1/44 (2013.01); H01L 23/585 (2013.01); H01L 27/1443 (2013.01); H01L 27/1446 (2013.01); H01L 31/02019 (2013.01); G01J 2001/446 (2013.01); G01J 2001/448 (2013.01)] 21 Claims
OG exemplary drawing
 
1. An ambient light sensor, comprising:
a plurality of pixels;
wherein each pixel comprises a photodetector; and
a readout circuit configured to determine an ambient light level, said readout circuit operating to:
reset a coarse value at the beginning of an exposure time; and
repeat the following steps over the exposure time:
connect the photodetector to a reverse bias voltage supply so that a voltage across the photodetector is reset to a reverse bias voltage level;
disconnect the photodetector from the reverse bias voltage supply so that the voltage across the photodetector decreases in response to absorbed photons and collection of generated carriers;
compare the voltage across the photodetector to a threshold to generate a result having a signal level; and
increment the coarse value when the signal level of the result of the comparison changes;
wherein the coarse value at the end of the exposure time is indicative of the ambient light level.