AN725 데이터 시트보기 (PDF) - Silicon Laboratories

부품명

상세내역

제조사

AN725

ADVANCED LOW POWER TECHNIQUES FOR SiM3L1XX DEVICES

Silicon Laboratories 

AN725

5.4.2. Contrast Modes

The LCD0 module features four contrast modes: bypass, minimum, constant, and auto-bypass. The selection of

the contrast mode is governed by the application requirements and LCD specifications. The power consumption of

these modes will vary due to the internal charge pump and resistor string that generates the VLCD voltage.

Reducing the time this hardware is active will reduce power consumption.

In bypass mode shown in Figure 11, the VLCD voltage tracks with the VBAT input voltage. This mode reduces

power consumption by disabling the LCD charge pump and is most appropriate for systems where the VBAT

voltage is relatively constant.

VBAT

VLCD

Figure 11. LCD0 Bypass Contrast Mode

In minimum contrast mode shown in Figure 12, the VLCD voltage will track the VBAT voltage to a minimum level

set by the VBAT monitor threshold (VBMTH). When VBAT is equal to this voltage, VLCD will switch to the contrast

level set by the CTRST field. The threshold and contrast voltages do not have to be set to the same level, as

shown in Figure 13. If the VBAT voltage goes back above the threshold, the LCD contrast charge pump will turn off.

This mode is most efficient for systems that can use the battery voltage most of the time but require a minimum

contrast level to see the LCD segments.

VBAT

VLCD

minimum level set by

CTRST

Figure 12. LCD0 Minimum Contrast Mode

VBAT

VLCD

CTRST

VBMTH

Figure 13. LCD0 Minimum Contrast Mode with Different Threshold and Voltage Settings

Rev. 0.1

23

Share Link: