Datasheet

Chapter 9 Liquid Crystal Display Driver (S08LCDV1)
MC9S08LC60 Series Data Sheet: Technical Data, Rev. 4
152 Freescale Semiconductor
9.4.4.1 LCD Charge Pump and Voltage Divider
The LCD charge pump is a voltage tripler. Using the voltage divider and the charge pump, the LCD module
can effectively double or triple V
LCD.
This LCD module configurability makes the LCD module
compatible with both 3-V or 5-V LCD glass.
The LCD module charge pump mode select bit (LCDCPMS) in the LCDSUPPLY register configures the
LCD module operational mode as a voltage doubler or a voltage tripler. In Figure 9-17, LCDCPMS bit
signal is used to control switches within the voltage divider block to enable or disable the two-thirds (2/3
* V
LCD
) voltage divider. If LCDCPMS = 0, the LCD module is configured as a voltage doubler
(recommended to V
LCD
be used with 3-V LCD glass) by enabling the voltage divider. If LCDCPMS = 1,
the LCD module is configured as a voltage tripler (recommended to be used with 5-V LCD glass) by
shorting the voltage divider. The LCDCPMS configuration depends on the LCD panel operating voltage
specification in the design application.
9.4.4.1.1 LCD Charge Pump Enabled
The LCDCPEN bit in the LCDSUPPLY register enables the charge pump. When charge pump is enabled
(LCDCPEN = 1), V
LL1
, V
LL2
, and V
LL3
are will be generated internally.
9.4.4.1.2 LCD Charge Pump Disabled
When charge pump is disabled (LCDCPEN = 0), V
LL1
, V
LL2
, and V
LL3
are not generated internally.
Instead, V
LL1
, V
LL2
, and V
LL3
must be provided by external hardware.