National Semiconductor Corporation

Ying Quan Zhong

William E Miller

Richard E Crippen

Franklin S Ho

A voltage supply circuit for an LCD driver employs two voltage dividers. A low current voltage divider includes resistive elements having a high resistance, thus providing a bias voltage with a low current. A high current voltage divider includes resistive elements having low resistances, thus providing a bias voltage with a high current. The high current voltage divider provides bias voltage levels with high current at the beginning of each time phase change. Thus, the liquid crystal display receives a high current when updating the bias voltage levels on the LCD, thereby producing a fast settling time. When the bias voltage levels are held constant, however, only the low current voltage divider provides the bias voltage levels to reduce power consumption. A halt mode prevents the liquid crystal display and driver from consuming any power by disconnecting both voltage dividers from the voltage source when in sleep mode. A voltage drop mode produces a reduction in the bias voltage levels by placing another voltage drop in series with the voltage dividers.

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Fremont, CA, United States of America

Ying Quan Zhong