I'm designing a circuit for a custom event console (SMPS', chip reader, screen, controllers, NFC,..) which I would like to power on/off in the same way a laptop or tablet is powered on/off (hold pushbutton for x time). It runs on 12V and thus should be quite comparable to a laptop. My research has been fruitless so far, so I've come here for suggestions Also, I'm aware I could use flip-flops, n- and p-mosfets in different arrangements to accomplish this, but I would like just one IC (a few extra Rs, Cs and Qs are no big deal) since the board I'm working on is quite small. Thanks!
You need a couple of things:
- standby voltage source
- standby controller
The standby voltage source can sometimes come for free if you have a DCDC converter in your system: pick off that regulator to run your controller.
As for the controller itself, a small micro like ATTiny or PIC can do this.
But there is another way. Arrange your power control so that the pushbutton holds on the power. Meanwhile, your host system controller also reads the button as well once it's powered on. In this way you don't need a standby controller at all. This, by the way, is exactly how a phone power button works.
This Q seems relevant: Latching Soft ON/OFF Button