Level Shifter With Low Voltage Loss
AssigneeParade Technologies, Ltd.
InventorsLiang Xu, Hongquan Wang
Life of this patent
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Abstract
A system and method are disclosed for level shifting a DDC bus with a low voltage loss. A pull up circuit includes an NMOS transistor, a PMOS transistor and resistor. An NMOS pull up gate is also included in line with the DDC bus. When powered, the level shifter adjusts the voltage of transmitted signals to match the voltage of a receiving device. The resulting adjusted is slightly lower due to a threshold voltage lost across one or more transistors. Additionally, when unpowered, the level shifter releases the signal transmission line. Unadjusted signals can then be transmitted without consumption of power by the level shifter.
Claims20
A method for level shifting a display data channel with low voltage loss, the method comprising:
- receiving a first signal from a first video interface, the first video interface operating at a high voltage level, the first signal at the high voltage level;
- reducing the voltage of the first signal to better match the voltage of a second video interface, the second video interface operating at a low voltage level, the low voltage level between zero and the high voltage level;
- and
- transmitting the first signal with a reduced voltage level to the second video interface.
An apparatus for level shifting with low voltage loss, the apparatus comprising:
- a display data channel coupled to a source operating at a first voltage level and a sink operating at a second voltage level;
- an NMOS pass gate in line with the display data channel and coupled to the sink;
- and
- a pull up circuit coupled to the display data channel between the source and the NMOS pass gate, the pull up circuit comprising an NMOS transistor, a PMOS transistor and a first resistor between the NMOS transistor and PMOS transistor, wherein the PMOS transistor is coupled to a first voltage source at the first voltage level.
An apparatus for level shifting with low voltage loss, the apparatus comprising:
- a means for receiving a first signal from a first video interface, the first video interface operating at a high voltage level, the first signal at the high voltage level;
- a means for reducing the voltage of the first signal to better match the voltage of a second video interface, the second video interface operating at a low voltage level, the low voltage level between zero and the high voltage level;
- and
- a means for transmitting the first signal with a reduced voltage level to the second video interface.
Dependencies are inferred from the claim text.