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Any LCD Bias IC allow VCOM to be derived from external POL?

k_nov
Prodigy 10 points
Other Parts Discussed in Thread: TPS65150, TPS65101, TPS65146

I have a circuit (see attached) provided by an LCD manufacturer that illustrates using the POL signal from the display to derive the VCOM signal.  From what i've read, LCD Bias ICs generate VCOM from the high bias voltage.  Is it possible to instead feed the POL signal into one of these ICs to generate the VCOM signal?  Is there a version of these ICs that provides a 'discrete' opamp that can be utilized as illustrated in the attached schematic?

For reference, VR50 adjusts the gain of VCOM which affects the color saturation.  VR51 provides contrast adjustment by level shifting the VCOM signal.

Thanks!

  • 0
    TI__Guru 58225 points

    Hello k_nov,

    It is true that you can derive the VCOM signal from the source line signal and for the big portion of your VCOM signal this is done with the resistors connected from VDD and VGL to A+in. Then it is good practice and increases the functionality of the LCD to use as well feedback from the panel, which is done with the POL signal, I think.

    So in general if this is the recommended circuit from the LCD vendor, I would stick to it, because it is a prooven solution.

    For sure there are parts available having VCOM buffers as well as positive and negative charge pump drivers and a boost converter integrated. You might have a look to TPS65101, TPS65146 or TPS65150.

    Best regards,
    Brigitte