Wake-up source with nRF52 capacitive touch and current consumption

RE: Wake-up source with nRF52 capacitive touch and current consumption

bjorn-spockeli — Tue, 25 Jul 2017 12:09:06 GMT

No, the nEF51 capsense example only uses one TIMER instance, so the TIMER run current does not need to be multiplied with the total number of buttons.

RE: Wake-up source with nRF52 capacitive touch and current consumption

MANGO — Mon, 24 Jul 2017 16:13:37 GMT

Hi, Bjørn. Thanks for your profound answer!

About the 320µA, this is not proportional regardless of the number of touch buttons, right?

For instance, if 4 buttons are used, the HFCLK run current is same but the timer run current should be multiplied, I guess? 250µA + 70*4µA = 530µA?

To be sure, the best answer will be the measured value after creating the PCB.

I just want to estimate before creating one.

-Best Regards

RE: Wake-up source with nRF52 capacitive touch and current consumption

bjorn-spockeli — Mon, 24 Jul 2017 14:06:16 GMT

Hi Mango,

you will not be able to wake the nRF52832 up from System OFF since in this state only the wake-up circuitry (GPIO DETECT mechanism, LPCOMP and NFC Sense mechanism) is active.

This means that you will not be able to source any current from the GPIO pins or use the TIMER peripheral to perform measurements while the nRF52832 is in System OFF mode.

Waking the nRF52832 up from System ON: Low power mode should not be an issue.

As for the current consumption, we have not done any measurements on this, but since you're using the TIMER peripheral, which requires the HFCLK, then you're going to see a run current of at least 250uA (HFCLK run current) + 70uA ( TIMER run current @ 16MHz) = 320uA.