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Topic: Minimum safe voltage from LIPO to read/write sd card in MKRZERO (Read 604 times) previous topic - next topic

MicheleMaris

Dear All.

I am working at a simple datalogger based on MKRZERO.

The logger will be powered by a LiPO battery through the board 3.7V power port

I want not to try to write data on the SD within the MKRZero when the voltage of the LiPO becomes too low.

For this reason, I monitor the battery voltage through the ADC_BATTERY, stopping any operation on the SD when the voltage is too low.

Of course, the problem is to fix the threshold voltage.

According to the MKRZERO schematic, the voltage from the LiPO battery is reduced to the required 3.3V through an AP7215 voltage regulator.

I found a datasheet stating that the dropoff voltage Vdrop of the regulator is between
60 and 100 mV when the drained current from the regulator is 30 mA, and 100 to 250 mV when the drained current is about 100 mA.

So I guess that a safe representative Vdrop is 150 mV

In this case, I would have to allow the logger to work whenever

Vbat > 3.45 V.

Is there somebody who knows some better specification?

Is there some reason to stop at a higher Vbat level? Or is it possible to go lower?

Thank you very much
M.M.




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