Micron Technology Incorporated

Aptina Imaging Corporation

Alex Krymski

Sandor L Barna

Sungkwon C Hong

A pixel cell has controlled photosensor anti-blooming leakage by having dual pinned voltage regions, one of which is used to set the anti-blooming characteristics of the photosensor. Additional exemplary embodiments also employ an anti-blooming transistor in conjunction with the dual pinned photosensor. Other exemplary embodiments provide a pixel with two pinned voltage regions and two anti-blooming transistors. Methods of fabricating the exemplary pixel cells are also disclosed.

Wide dynamic range sensor having a pinned diode with multiple pinned voltages

The present invention provides an improved column readout circuitry and method of operation which minimizes substrate and other common mode noise during a read out operation. The circuit improves the consistency of the pixel to pixel output of the pixel array and increases the dynamic range of the pixel output. This is accomplished by obtaining a differential readout of the reset signal and integrated charge signal from a desired pixel along with the reset signal and charge signal from a reference circuit. In this manner common mode noise can be minimized by a combination of signals from the desired and reference pixels in the sample and hold aspect of the column circuitry. In one exemplary embodiment of the invention, a 3T pixel arrangement is used. In another exemplary embodiment, a 4T arrangement is used. Additional exemplary embodiments provide differential column readout circuitry that can be used with any two signal sources.

Differential column readout scheme for CMOS APS pixels

A ramp generator includes an array of capacitors having a common top plate that provides a ramp output signal. Each of the capacitors has a bottom plate switched sequentially between a low reference voltage and a high reference voltage in response to a value in a shift register. For an upward ramp, capacitors can be switched to their high reference voltages in succession, increasing the output voltage on the common top plate; for a downward ramp, capacitors can be switched to their low reference voltages in succession, decreasing the output voltage. The capacitors can be switched by a multi-bit shift register, each bit of which controls one capacitor's voltage. Each time a clock signal is applied to the shift register, a value in the shift register shifts another capacitor between its low and high reference voltages.

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La Crescenta, CA, United States of America

Alex Krymski