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I'm designing a PCB. I want to turn the ADS1120 ADC off/on using the SAMD21G microcontroller. The ADC has two power inputs, 3.3V analog and 3.3V digital. The 3.3V analog is connected to an LDO that has an enable pin which is connected to one of SAMD21G pins, so that power pin I can turn on and off. For the 3.3V digital however, I can't turn the LDO on and off as it connects to other components. I was thinking about using two MOSFETS one PMOS connected to 3.3V digital with its gate connected to the drain of an NMOS (with gate connected to pin of SAMD21G) that way it acts as kind of an enable. I also thought about using a tri-state buffer with enable pin (connected to SAMD21G.) I'm not sure if that is a good idea, though. Are tgere any other ways I could do that? Which would be the best way?

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JRE
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Mostafa Ibrahim
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1 Answers1

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Sounds like a generally bad ideas; don't switch the power to something that you can even simpler put into a power-down mode.

In power down, your adc uses 400nA typically; the whole support logic you'll need to switch it externally will quite likely be in the same region of current consumption.

Since your digital LDO is used for other things as well, this will not even be noticeable as unnecessary quiescent current.

TL;DR: don't do anything, just send the SHUTDOWN command to the ADC when you don't need it.

Marcus Müller
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