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I am trying to turn on or off a Raspberry Pi Pico using a Raspberry Pi Model 3.

The Raspberry Pi Pico seems to have a 3.3V_EN ping which is basically the 3.3V regulator enable pin (3V3_EN) pulled up to 5V through a 100K resistor internally.

I am confused how to use this pin using a 3.3V logic of the Raspberry Pi model 3 gpio pins to turn on or off the regulator inside the Pico.

From what I can see, the 5V will sink to ground if I pull the Raspberry Pi pin to ground but this pin is designed for 3.3V not 5V. It might damage the pin. On the other hand, what state should I keep the gpio pin so that it is basically floating and the Pico regulator is ON because of the internal pull-up. Kind of confused with this. Maybe I am missing something.

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Generally it is a bad idea to apply a voltage in excess of the stated max voltage to a chip. However, since the current is very small via the 100k to 5V, you might be able to get away with it. However, most cmos ics have protection diodes on their pins and these will clamp the voltage to just above the 3V3 rail. You will need to read the richtek datasheet on the regulator to determine if 3V3 is an adequate voltage to enable the regulator.

Or just get a small signal mosfet like a 2N7000, BSS138 etc and use it as a level shifter. The pi gpio to the gate, pico enable pin to drain. Source to gnd. A 100k resistor from ground to the gate will ensure the mosfet is turned of during reset.

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    \$\begingroup\$ What if I use a voltage divider from the 3.3V_EN pin with a 200K resistor to bring down the overall logic of that pin to 3.3V? Will this method work and be safe for all the devices in the network? I mean the regulator, pi gpio pin and the upstream 5V voltage source. \$\endgroup\$
    – Roger Dsuza
    Jun 22, 2021 at 14:01
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    \$\begingroup\$ I’m refraining on reading the regulator datasheet so you can find the information you need to answer your question. There will be a spec for the minimum Vih for the enable pin. If your circuit can guarantee you exceed this value when you want the node high and when you want the node low, that thr Vil spec is observed. \$\endgroup\$
    – Kartman
    Jun 22, 2021 at 14:07

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