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LCDCAP vs R33/R23/R13/R03 resistor ladder

dayberry
Prodigy 250 points
Other Parts Discussed in Thread: MSP430F47166

I am using the MSP430F47166 with LCD_A module driving a 4-mux LCD and would like to control the contrast via software with the VLCDx bits. The project was initially designed with a resistor ladder of 680 kOhm resistors, with a 0 ohm from R03 to ground. The user's guide mentions the necessity of a 4.7uF cap or larger on LCDCAP/R33 if the internal charge pump is used. Should I have the resistor ladder AND the 4.7uF cap, or are these components mutually exclusive?

  • 0
    Expert 2080 points

    No they are not exclusive, you can have your resistor ladder for defining the bias voltage, and the 4.7uF for using the internal charge pump. In fact, you have to connect all of them

    The thing to know is that the voltage on the R33/LCDCAP pin, is the maximun voltage for the ladder, so its logically the voltage from the charge pump too.

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