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LCD interface voltage?

tojijn Twu
Intellectual 280 points

Dear community expert:

Recently I met a puzzle.

LCD need 5 voltage to have higher contrast. But The TI chip F6XX output are only 3.3V.

I am forced to give up the case. Do any expert can give me some opinion.

( I find there are many posts talk about this problem.but don't get any response.)

   THANKS

  • 0
    Guru 58965 points
    Some LCDs come assembled with a controller on the back. The controller usually only needs one power source and delivers what ever the LCD Glass needs. Read the data-sheet of that LCD assembly.

    Some LCDs come naked and need multiplexed signals and different voltages. The MSP430F6xxx chips has on-chip controllers to handle them. Read the F6xxx User's Guide LCD Controller Chapters.
  • 0 in reply to old_cow_yellow
    Intellectual 280 points
    Thanks first.
    My condition is the second.
    I have succeed drive the 3.3V naked LCD. But the color contrast is too low.
    The LCD provider express that 5V drive signal will have the best color contrast.
    Do the F6xx has the possibility to provide 5V signal?
  • 0 in reply to tojijn Twu
    Guru 58965 points

    Sorry. There may be some misunderstanding.

    What I called naked LCD may need 5 different voltages, not 5V. The interface signals may look like this:

    Is that what you got? (I do not think so.) It will need a few COMx multi-level signals and tens of Sy multi-level signals for interfacing. (Again, read the F6xxx User's Guide.) Those LCD Glasses are usually custom made and not for retail.

    I think most likely you have a LCD with a controller included.In that case, you only need a few digital interface signals (5V and 0V). Try fined the manufacturer and part number, a data-sheet or something about it and I may be able to help you. I think you may be able to use 3.3V interface signal and a -2V contrast bias which can be generated with a PWM signal form your MSP430 and a few diodes and capacitors.

    I have a "LCD" on one of my pens. I also have a "LCD" on my desktop. The first one has 32 "segments" and shows me time of the day using only a hearing aid battery. The second one has millions of "pixels" and shows me color pictures but it uses 110VAC. Your LCD must be somewhere between those two. You need to describe it.

  • 0 in reply to old_cow_yellow
    Intellectual 280 points

    You are so nice to discuss with me.

     

    FIRST TYPE

    LCD with controller is no problem for anyone. like following.

    It’s contrast can adjust with a various resistence .(Potentiometer).

    The interface is 3V or 5V. I am not mean this type.

     ----------------------------------

     SENOND TYPE:

    LCD without controller. Just as the waveform you mentioned .I know these waveform.

    The LCD is customized.

    I have see the LCD demo of manufacturer. and know the difference between 3V and 5V.

    It can be drive with 3V (V1=3V),but the color contrast is not good.

    If we drive with 5V(V1=5V).the contrast is very good  to identify.

     

    So I want to drive this 5V LCD without controller with MSP430F6XX directly. Is it possible?

  • 0 in reply to tojijn Twu
    Guru 58965 points

    Good. Specifically, which F6xx chip are you using?

    There is a charge-pump in the on-chip LCD controller. It generates the voltage needed for contrast control. The voltage can be adjusted by setting the LCD bias voltage control register. This register is called LCDxVCTL where x can be B,C,D,etc. depends on the specific LCD controller. Detailed information is in the User's Guide


    Edited in Red

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