System and method for providing bias voltages to pad logic of an LCD controller
AssigneeSilicon Laboratories Inc.
InventorsThomas S. David, Douglas Piasecki
Life of this patent
Estimating the term…
Abstract
An LCD controller includes at least one I/O pad for providing an LCD drive voltage in an LCD mode of operation. I/O pad logic drives the at least one I/O pad responsive to a provided bias voltage. Voltage selection logic selects a higher voltage between an LCD drive voltage and an externally provided system voltage as a first voltage. Bias voltage logic selects one of the system voltage or the first voltage as the bias voltage for the I/O pad logic. The system voltage is selected as the bias voltage for the I/O pad logic in a non-LCD mode of operation for the I/O pad and the first voltage is selected for the bias voltage for the I/O pad logic in the LCD mode of operation for the I/O pad.
Claims20
An LCD controller, comprising:
- at least one I/O pad for providing an LCD drive voltage in an LCD mode of operation for the I/O pad;
- I/O pad drive logic for driving the at least one I/O pad responsive to a provided bias voltage;
- voltage selection logic for providing a higher of the LCD drive voltage and a system voltage as a first voltage;
- bias voltage logic for providing one of the system voltage or the first voltage as the bias voltage for the for the I/O pad logic, wherein the system voltage is provided as the bias voltage for the I/O pad logic in a non-LCD mode of operation for the I/O pad and the first voltage is provided as the bias voltage for the I/O pad logic in the LCD mode of operation for the I/O pad.
An LCD controller, comprising:
- a plurality of I/O pads for providing an LCD drive voltage in an LCD mode of operation for the I/O pads;
- I/O pad drive logic associated with each of the plurality of I/O pads for driving the associated I/O pad responsive to a bias voltage;
- an analog multiplexer for selecting the LCD drive voltage from a plurality of input voltages from a charge pump responsive to the bias voltage;
- voltage selection logic for providing a higher of the LCD drive voltage and a system voltage as a first voltage;
- first bias voltage logic for providing one of the system voltage or the first voltage as the bias voltage for the analog multiplexer, wherein the system voltage is provided responsive to an indication that LCD controller is in a non-LCD mode of operation and the first voltage is provided responsive to an indication the LCD controller is in the LCD mode of operation;
- and
- second bias voltage logic associated with each of the plurality of I/O pads for providing the system voltage or the first voltage as the bias voltage for the associated I/O pad drive logic, wherein the system voltage is provided as the bias voltage for the associated I/O pad drive logic responsive to an indication the associated I/O pad is not driving a connected LCD and the first voltage is provided as the bias voltage for the associated I/O pad drive logic responsive to an indication the associated I/O pad is driving an LCD.
A method for selecting a bias voltage for I/O pad drive logic of an LCD controller, comprising the steps of:
- selecting a higher voltage between an LCD drive voltage and an externally provided system voltage;
- determining whether an I/O pad of the LCD controller is in an LCD mode of operation or a non-LCD mode of operation;
- selecting the externally provided system voltage as the bias voltage of the I/O pad drive logic if the I/O pad of the LCD controller is in the non-LCD mode of operation;
- and
- selecting the selected higher voltage as the bias voltage of the I/O pad drive logic if the I/O pad of the LCD controller is in the LCD mode of operation.
Dependencies are inferred from the claim text.