ATmega169P
22.3.3
1/3 Duty and 1/3 Bias
1/3 bias is usually recommended for LCD with three common terminals (1/3 duty). Waveform is
shown in Figure 22-5. SEG0 - COM0 is the voltage across a segment that is on and SEG0-
COM1 is the voltage across a segment that is off.
Figure 22-5. Driving a LCD with Three Common Terminals
V
V
/ V
/ V
GND
LCD
LCD
LCD
LCD
LCD
LCD
2
1
2
1
/ V
3
3
SEG0
COM0
SEG0
COM1
/ V
3
3
GND
V
V
LCD
LCD
2
1
2
1
/ V
/ V
3
LCD
3
LCD
/ V
/ V
3
LCD
3
LCD
GND
GND
V
V
LCD
LCD
2
1
2
1
/ V
/ V
3
LCD
3
LCD
/ V
/ V
3
LCD
3
LCD
SEG0 - COM0
SEG0 - COM1
GND
GND
1
1
- / V
- / V
- / V
-V
3
LCD
LCD
LCD
3
LCD
LCD
LCD
2
2
- / V
3
3
-V
Frame
Frame
Frame
Frame
22.3.4
1/4 Duty and 1/3 Bias
1/3 bias is optimal for LCD displays with four common terminals (1/4 duty). Waveform is shown
in Figure 22-6. SEG0 - COM0 is the voltage across a segment that is on and SEG0 - COM1 is
the voltage across a segment that is off.
Figure 22-6. Driving a LCD with Four Common Terminals
V
V
LCD
LCD
LCD
LCD
LCD
LCD
2
1
2
1
/ V
3
/ V
3
GND
/ V
3
/ V
3
GND
SEG0
COM0
SEG0
COM1
V
V
/ V
LCD
LCD
2
1
2
1
/ V
3
LCD
3
LCD
LCD
/ V
3
/ V
3
LCD
GND
GND
V
V
/ V
LCD
LCD
2
1
2
1
/ V
3
LCD
3
LCD
LCD
/ V
3
/ V
3
GND
LCD
SEG0 - COM0
SEG0 - COM1
GND
1
1
- / V
3
- / V
3
-V
- / V
3
- / V
3
-V
LCD
LCD
LCD
LCD
LCD
LCD
2
2
Frame
Frame
Frame
Frame
237
8018A–AVR–03/06
ATMEL [ ATMEL ]
