Reduction of the effect of AVDD power supply variation on gamma reference voltages and the ability to compensate for manufacturing variations
View Patent ↗The invention relates to an apparatus for electronic display comprising means for generating liquid-crystal-display (LCD) input signals, a LCD panel operable to display a color image according to the LCD input signals, a circuit operable to generate a plurality of sets of gamma correction values for gamma correction of the LCD input signals, and means for eliminating dependency of the plurality of sets of gamma correction values on a supply voltage (AVDD) of the circuit.
1. An apparatus for electronic display comprising:
a device for generating LCD input signals;
an LCD panel operable to display a color image according to the LCD input signals;
a circuit operable to generate a plurality of sets of gamma correction values for gamma correction of the LCD input signals; and
wherein the circuit further comprises one or more gamma reference controllers that are capable of reducing dependency of the plurality of sets of gamma correction values on a supply voltage (AVDD) based on common mode rejection ratio of a pseudo-differential circuit,
wherein the one or more gamma reference controllers comprise:
a plurality of non-volatile analog storage cells for generating the plurality of sets of gamma correction values, and
at least one non-volatile analog reference cell for forming pseudo-differential circuitry with the plurality of non-volatile analog storage cells to reduce effect of AVDD variations on gamma reference voltages,
wherein output of the plurality of non-volatile analog storage cells and output of the at least one non-volatile analog reference cell are coupled to inputs of the of the pseudo differential circuit, wherein output of the pseudo differential circuit is gamma output least one non-volatile analog reference cell are coupled to inputs of the pseudo differential circuit, wherein output of the pseudo differential circuit is gamma output,
wherein a portion of the pseudo-differential circuitry comprises a first non-volatile analog storage cell that comprises a first floating gate transistor and generates a first output voltage and a second non-volatile analog storage cell that comprises a second floating gate transistor and generates a second output voltage:
the first and the second floating gate transistors are programmed wherein the difference between the first output voltage and the second output voltage generates a gamma output,
wherein common mode variations of the first voltage output and the second voltage output due to (1) power supply (AVDD) and (2) temperature are compensated, and
wherein the gamma output represents a pre-determined gamma value that is independent of the (1) power supply (AVDD) and (2) temperature based on common mode rejection capability of the pseudo-differential circuit.