As an experiment, we want to implement soft power off for nRF52 with external components. We want to keep the entire circuitry entirely switched off, and after a press of a pushbutton, we want to turn on an nRF52 and do a short transmission.
This case we don't want to use the sleep mode of the chip - rather switch it off entirely. The reason is, we have a use case allows us to do so, and with this, we could use an even smaller on-board battery (e.g not coin cell)
We wanted to design a soft power latch circuit based on research on the Internet, we were able to test them, but were not able to achieve zero consumption. What designs we tried: www.instructables.com/.../ www.youtube.com/watch
And our design:
Most of the time the controller is totally shut down. When the user pushes the button the current start to flow and the controller comes alive through the transistors and capacitors. Then it controls its own power and keep itself alive through a GPIO: in the first lines of the main() function we pull up for the NFET. After the operation (max. a couple of secs) the controller shuts down its own power, through the GPIO by releasing it.
We were able to achieve success (turning on with the button then shutting down through code) with some design, however we realized that some current "leaks" and flow through the positive terminal of the controller when the nRF chip is switched off. (The GPIO pin that we use to control the mechanism has current even was switched off state.)
Yeah.. we guess it's "undefined" what a GPIO does in a switched off state, but still interested in the softpower..
It is possible that, we can switch off the current entirely? Is there a common and widely used circuit and method for this? Any opinions?
Thank you, Adam
