NXP Semiconductors MPC5606S - Contrast Adjustment

LCD Driver (LCD64F6B)
MPC5606S Microcontroller Reference Manual, Rev. 7
814 Freescale Semiconductor
22.5.3 Contrast adjustment
The LCD Driver module offers two different ways to adjust contrast:
22.5.3.1 Adjusting the supply voltage (VLCD)
The VLCD voltage can directly be used as reference and source to drive the LCD segments. The contrast
could be easily adjusted by altering the voltage at the VLCD pin.
22.5.3.2 Adding contrast adjustment phases
Another way to adjust the contrast is to add another phase to the refresh cycle which keeps the voltage the
same on all frontplane and backplane electrodes (V
SS
in this case). This will contribute towards lowering
the V
ONRMS
and V
OFFRMS
voltages over the segment. For this reason, the whole frame is divided into
steps. The value from the Contrast Control register (LCC) determines how many of these steps are taken
by the contrast phase. Whenever the length of the contrast adjustment phase is changed, the length of the
other phases is automatically changed to ensure the frame length remains the same.
Example: A value of 256 in the Contrast Control (LCC) register will force the contrast phase to take
approximately a 256/2047 of the length of the whole frame.
Figure 22-23 shows an example of waveform with 1/1 duty and 1/1 bias ratios with the additional contrast
adjustment phases
Figure 22-23. Contrast adjustment phases
BP0
FPx (xxx0)
FPy (xxx1)
1 Frame
= Contrast Adjustment Phase
BP0
FPx (xxx0)
FPy (xxx1)
1 Frame