Power reduction technique for current mode digital-to-analog converters
AssigneeHewlett-Packard Company
InventorsJames S. Ignowski, Hugh Wallace, Stuart A. Bell
Life of this patent
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Abstract
A video DAC for driving video displays with reduced power dissipation is presented. This is accomplished using a dual driver circuit connected to a current mirror, the dual driver comprising a strong driver and a weak driver. The dual driver permits switching current between the video load and a dummy load. The current to the dummy load is disabled during periods when the video signal remains steady for a predetermined period of time. The dual driver, using the weak driver, disables the current to the dummy load during video blanking and synchronization periods. This scheme substantially reduces the power dissipation in the DAC.
Claims8
A video DAC having reduced overall power dissipation, the video DAC comprising:
- a current mirror having a current output and first and second inputs;
- and
- a dual driver circuit having an output, the output connected to the first input.
A video subsystem for driving a video display, the video subsystem resides within a computer system, the computer system having a CPU, the video subsystem comprising:
- front end logic, the front end logic receives video data from the CPU;
- a frame buffer connected to the front end logic, the frame buffer receives the video data from the front end logic;
- a video DAC connected to the frame buffer, the video DAC converts the video data into an analog signal, the video DAC having at least one current cell, the at least one current cell switches current between a dummy load resistor and the analog signal using a dual driver circuit, the dual driver circuit having a strong driver and a weak driver.
Dependencies are inferred from the claim text.