US 11,885,646 B2
Programmable active pixel test injection
Charles Myers, Portland, OR (US); Shunming Sun, Colorado Springs, CO (US); and Adam Lee, Portland, OR (US)
Assigned to Allegro MicroSystems, LLC, Manchester, NH (US)
Filed by Allegro MicroSystems, LLC, Manchester, NH (US)
Filed on Aug. 12, 2021, as Appl. No. 17/400,300.
Prior Publication US 2023/0051974 A1, Feb. 16, 2023
Int. Cl. G01D 18/00 (2006.01); H01L 27/146 (2006.01)
CPC G01D 18/00 (2013.01) [H01L 27/14609 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A detector system, comprising:
a photodetector;
an amplifier having an input to receive an output from the photodetector;
a discriminator to receive an output from the amplifier and generate an active output signal when the output from the amplifier is greater than a threshold; and
an injection circuit coupled to the input of the amplifier, wherein the injection circuit is configured to selectively inject a test pulse that mimics a pulse from the photodetector for verifying operation of the detector system,
wherein the injection circuit comprises:
an injection capacitor coupled to the input of the amplifier, wherein the injection capacitor is sized to mimic the pulse from the photodetector, wherein the amplifier comprises a transimpedance amplifier to convert an input voltage to an output current;
a logic gate to receive a step signal and pixel row and column signals for the photodetector within an array and output a step lim signal;
an inverter coupled to the output of the logic gate to generate an inverted step lim signal;
a first switch controlled by the step lim signal, wherein the first switch is coupled between a voltage injection signal and the injection capacitor;
a second switch controlled by the inverted step lim signal, wherein the second switch is coupled between the injection capacitor and a voltage reference,
wherein the step-lim signal and the inverted step lim signal are rate-limited to control a width of the test pulse and to control slope to shape an output from the injection capacitor.