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The purpose is to generate voltage supply for the LCD, normally a negative voltage -2 to -12 V for small grapic displays. Some displays have internal DC-DC converters for this, so they only need single voltage supply.
oh yuh, my microcontroller has 3 inputs V1, V2, V3. I didn't read the hardware spec.
And the LCD booster is mentioned in the spec as follows:
When a large panel is driven, the on-chip power supply capacity may be insufficient. If the power
supply capacity is insufficient when VCC is used as the power supply, the power supply impedance
must be reduced. This can be done by connecting bypass capacitors of around 0.1 to 0.3 µF to
pins V1 to V3, or by adding a split-resistance externally.
This is not a booster, but just a set of decoupling caps.
The internal LCD controlling voltages are probably made with a resistor divider network on-chip, and for peak currents this may not be stable enough. A capacitor on-chip takes too much precious space. That's why they want you to put a storage capacitor externally: to supply brief pulses of current when needed, while the on-chip power supply can refill the capacitor in the long run.
If this explanation isn't right, can you give the exact link to the datasheet and which page you're referring to?
custom LCD are type of capacitor and it need to be drived with AC signal's when you are using large area of LCD the controller don't have the capability to drive a large area ther for the booster is needed to increase the signal
Looke at Ti site on the MSP430 app note there is a good explanation on LCD driver
After looking at the datasheet, it is exactly what I mentioned: the V1, V2 and V3 LCD driving voltages are generated internally using a resistor divider network. If the LCD panel attached has a large area (capacitance), these internal resistor dividers may be too weak to drive the currrent pulses that occur when one of the 3 Vx voltages is switched to their column or row signals. In that case you can help the chip by adding external resistor divider (with a smaller resistor value, at the expense of a larger static power use) and/or some big storage caps that help to provide the current peaks.
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