Current spikes in low power modes

[Nordix]

Hi,

I am currently using a NRF52-DK board with a NRF52832. Measuring the power consumption I realized that at very low load, the internal power supply's mode of operation seems to change from its continuous mode to an "intermittent" mode with short current spikes. The level and frequency of the spikes varies with the load/SoC state. In deep sleep the time between the spikes is 268 ms with ~150 µA. I see this happening both, with LDO or DC/DC converter enabled. 

I found this and this old thread where it was said that this is due to a low-power "refresh" mode that the SoC changes to.

Is there more information about this somewhere? Is this some kind of charge-pump working principle?

Thank you very much in advance.

[Priyanka]

Hi,

It does not seem to be like a charge pump. Just that the capacitors are not connected when not required, to the voltage source. We do not seem to have a particular documentation, but I will check internally and get back to you.

Best Regards,

Priyanka

[Nordix]

Hi,
maybe "charge pump" was not the right term.
I would assume that it connects the supply input to some internal capacitors and adjusts the switching frequency to maintain a certain internal voltage in a range around the 1.3V core voltage.

I would be grateful if you have more information about this.

Best regards

[Priyanka]

Hi,

What happens in the refresh mode is that, the regulator charges the capacitor at DEC4:

and when it is fully charged, the regulator turns off. Then the charge in this capacitor is used by the chip and when the voltage goes below a certain level, the regulator is turned on and charges the capacitor again.

So there is no voltage boost. The DCDC regulator is just a voltage buck regulator.

Best Regrds,

Priyanka