Pre-charging a wide analog bus for CMOS image sensors
AssigneeSilicon Video Corporation
InventorChristian Boemler
Life of this patent
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Abstract
A video bus for an array of pixel amplifiers is designed for a minimum quiescent current draw. The pixel amplifiers (or column amplifiers) are designed with high impedance pull-ups and low impedance pull-downs to conserve over-all power dissipation. The video bus is provided with a high-impedance P-FET to reset the bus to drain voltage VDD for a very short time between the time one pixel (or column) is selected the time the next is selected, so that the video bus only has to be discharged through the low impedance N-FET. The bus does not have to be current-sourced by the P-FET.
Claims3
Analog bus for a solid state video imager, comprising
- a) one or more conductive channels;
- b) a plurality of column output amplifiers, each connected with a selected pixel of its associated column, and having a low-impedance amplifier device;
- c) respective switching means for selectively connecting outputs of the column amplifers to said one or more conductive channels;
- and
- d) a pre-charging high-impedance pull-up amplifier periodically charging up the one or more conductive channels between connections of said switching means.
Dependencies are inferred from the claim text.