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US 8,077,238 B2Granted
Wide dynamic range sensor having a pinned diode with multiple pinned voltages
AssigneeAptina Imaging Corporation
InventorsSungkwon C. Hong, Alex Krymski
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Abstract
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.
Claims8
A method of operating a wide dynamic range pixel cell, the method comprising:
- resetting a photosensor to remove all charge from the photosensor by setting a reset signal to activate a reset transistor and pulsing a transfer signal to activate a transfer transistor, the photosensor comprising first and second charge accumulation regions having respective first and second pinned voltages;
- exposing the photosensor to light during an integration period, the photosensor capable of converting the light into charges;
- draining said charges from said first accumulation region into said second accumulation region;
- setting an anti-blooming transistor to drain excess charge from the second charge accumulation region into a drain region;
- and
- performing a readout of the charges generated by the photosensor during the integration period, wherein a set point of the anti-blooming transistor is set by the respective first and second pinned voltages of the first and second charge accumulation regions.
3 more elements
Dependencies are inferred from the claim text.