what is the cr2032 power supply logic on the nrf52DK

[Anwar51]

This is the power supply system in the nrf52832 development board. The manual means that when 1 and 2 are not powered, 3 is used for power supply, that is, cr2032 is used for power supply.

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But when 3 is used for power supply, assuming 1、2 is closed. Vsupply is 0, so the AND gate and load switch are both closed

And the input pin of this load switch is Vsupply. When Vsupply has voltage, it means that 1 or 2 is used for power supply, so the output of the AND gate below is low level, nmos is not turned on, and pmos above is not turned on.

I feel that the logic is very messy when I sort it out. I hope friends who are familiar with hardware design can guide me.

I have just started PCB design and I am really confused. I feel that the idea is wrong

[Turbo J]

Take that as an example on what you don't want to do.

The key bit of information here is that V_in and V_out are reversed, and the datasheet of the TCK106AG clearly shows the diode between these pins.

Technically its not allowed by the datasheet to have voltage V_out bigger than V_in, but here this is how the circuit turns on when inserting the battery. The diode starts conducting, raising V_supply until the logic turns the power switch on (which eliminates the diode drop).

That one relies on the fact that a CR2032 has a rather low short circuit current capability, otherwise it could blow the diode (which characteristics are not specified in the datasheet as far as I can tell).

[Anwar51]

Thanks for the very clear explanation, the device schematic is so important, and the circuit design is so wonderful！