Datasheet

307
XMEGA B [DATASHEET]
8291B–AVR–01/2013
Figure 25-5. Driving an LCD With Three Common Terminals
25.4.4 1/4 Duty and 1/3 Bias
1/3 bias is optimal for an LCD displays with four common terminals (1/4 duty). The waveform is shown in Figure 25-6 on
page 307. SEG0-COM0 is the voltage across a segment that is ON” and SEG0-COM1 is the voltage across a segment
that is “OFF”.
Figure 25-6. Driving an LCD With Four Common Terminals
25.4.5 Low Power Waveform
To reduce toggle activity and hence power consumption, a low power waveform (LPWAV=1) can be selected. The low
power waveform requires two subsequent frames with the same display data to obtain zero DC voltage. Consequently,
the interrupt flag is only set every two frames. Default and the low power waveform is shown in Figure 25-7 on page 308
for 1/3 duty and 1/3 bias. For other selections of duty and bias, the effect is similar.
SEG0-COM0
Frame Frame
V
LCD
SEG0
COM0
2/3 V
LCD
GND
1/3 V
LCD
V
LCD
2/3 V
LCD
GND
1/3 V
LCD
V
LCD
2/3 V
LCD
GND
1/3 V
LCD
-1/3 V
LCD
-2/3 V
LCD
-V
LCD
Frame
Frame
V
LCD
SEG0
COM1
2/3 V
LCD
GND
1/3 V
LCD
V
LCD
2/3 V
LCD
GND
1/3 V
LCD
V
LCD
2/3 V
LCD
GND
1/3 V
LCD
-1/3 V
LCD
-2/3 V
LCD
-V
LCD
SEG0-COM1