Main power and battery power selection circuit

[paul0208]

Hi,

I'm using nRF52805.

The main power is 3.3V LDO output.

When main power is out, the battery(3V, Coin battery) should be a power source of nRF52805.

But, when battery power is used, nRF52805 will enter into sleep mode while RTC is active.

What is the recommend circuit for these option?

BR

Paul

[Priyanka]

Hi,

In order to switch the supply, you could use a relay circuit, but a hot swap should be properly tested as sometimes this can result in a brown-out reset (depending on your device).

You can take a look at the Hot Swap controllers too.

As for sleep mode, if you want your system to go to sleep when mains are out, you could have a check at the GPIO pins. So if the main power is active, then the GPIO pins are high and system can come out form sleep mode and vice versa.

But if you want to go to sleep whenever it is battery powered, then you should define some way for the system to understand this switch from mains to battery. But for this, you might have to use an external circuit for this, maybe even a custom IC for this.

Regards,

Priyanka