New soft power circuit

[samchoy88]

I would like to implement the following soft power circuit and solve below issue:

• JP1 made circuit operate at 3.6V instead of 3.3V #117
• SW_PWR cannot detect button action #116

I choose NAND gate instead of OR gate and made all input pulled up by 10K resistor.

[charlespax]

My only concern is pullup resistor on PWR_ONOFF is drawing 0.33 mA while the device is on. I suppose that's not a very large number. What is maximum practical value of that pullup resistor?

Here's what the power on sequence looks.

A   B   Y
H   H   L   <-- SW_PWR is not pressed, device is off. Device if off.
H   L   H   <-- SW_PWR is pressed, device is off. User presses and holds the power button.
L   L   H   <-- SW_PWR is pressed, device is on. Device boots up and enables power. User is still holding power button.
L   H   H   <-- SW_PWR is not pressed, device is on. User releases power button.

[samchoy88]

I think it can be 100K for pull up, as it only connect a logic which has high input impedance.

[charlespax]

Cool. Let's make that change in Electronics version 0.10.

[charlespax]

Done. Closing issue.