ATmega3290P datasheet(230/385 Pages) ATMEL

230 / 385 page

230

8021E–AVR–07/09

ATmega329P/3290P

when using 1/3 duty. To achieve satisfactory contrast, all segments on the LCD display must

therefore be able to be fully charged/discharged within 2 or 2.7ms, depending on the number of

common pins.

22.2.9

Minimizing power consumption

By keeping the percentage of the time the LCD drivers are turned on at a minimum, the power

consumption of the LCD driver can be minimized. This can be achieved by using the lowest

acceptable frame rate, and using low power waveform if possible. The drive time should be kept

at the lowest setting that achieves satisfactory contrast for a particular display, while allowing

some headroom for production variations between individual LCD drivers and displays. Note

that some of the highest LCD voltage settings may result in high power consumption when V

is below 2.0V. The recommended maximum LCD voltage is 2*(V

CC - 0.2V).

22.3

Mode of Operation

22.3.1

Static Duty and Bias

If all segments on a LCD have one electrode common, then each segment must have a unique

terminal.

This kind of display is driven with the waveform shown in Figure 22-3. SEG0 - COM0 is the volt-

age across a segment that is on, and SEG1 - COM0 is the voltage across a segment that is off.

Figure 22-3. Driving a LCD with One Common Terminal

22.3.2

1/2 Duty and 1/2 Bias

For LCD with two common terminals (1/2 duty) a more complex waveform must be used to indi-

vidually control segments. Although 1/3 bias can be selected 1/2 bias is most common for these

displays. Waveform is shown in Figure 22-4. SEG0 - COM0 is the voltage across a segment that

is on, and SEG0 - COM1 is the voltage across a segment that is off.

VLCD

GND

VLCD

GND

VLCD

GND

-VLCD

SEG0

COM0

SEG0 - COM0

Frame

VLCD

GND

VLCD

GND

SEG1

COM0

SEG1 - COM0

Frame

ATmega3290P Datasheet(PDF) 230 Page - ATMEL Corporation

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