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Topic: Battery powered MCU with 3V3 LCD module (Read 88 times) previous topic - next topic

luxon

Hello,

I am building a low power system with ATmega328 and 3V3 1602 LCD module. Everything will be powered by 3xAAA cells. MCU will sleep most of the time and will be turned on aprox. one time in a day for 15 seconds or less. Current consumption when awake is less than 10 mA.

The idea is to power the MCU directly from the battery pack, so from aprox. 4.5 V with new batteries to aprox. 2.7 V when cells will be almost empty.

LCD will be powered through 3V0 lowIQ LDO (TPS706), which would be disabled by MCU when in sleep mode.

My main concern is the logic levels to drive the LCD. With full battery, the voltage levels from the MCU will be slightly less than 4.5 V, but the LCD will be powered with 3V0 LDO. The datasheet for LCD says max VCC can be 7 V but max voltage for logic level should be the same as VCC voltage (which would be 3V).

What would be better solution in that case? To use logic level converter or power everything (also mcu) from 3V0 LDO?

jremington

#1
Mar 14, 2019, 12:10 am Last Edit: Mar 14, 2019, 12:31 am by jremington
Both solutions will work fine. At that extremely low duty cycle, batteries might last for a couple of years either way.

If the processor is running from 3.3V, consider powering the LCD through an I/O pin.
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