PPK2 strange current reporting after DUT goes into low power state

[DevinCallahan]

Hello!

I am starting to profile our device using the PPK2 and I am seeing some strange measurements when the device goes into its low power mode.

I'm attaching an image of what I mean:

The dense set of "spikes" at the end of the capture don't seem to correspond to anything in my system.

If I DON'T have the device go into its low power mode the capture looks like:

I am assuming the auto-ranging is struggling in this case, as the device moves from the mA range to 1-2uA in the low power state.

Is there something I can try to do to get rid of the "spikes" the current probe is reporting?

Bonus question:

Are the sample duration limits in the Power Profiler app set by some constraint in the PPK2 hardware or just the amount of RAM the host PC has to spare?  I have seen how I can modify the JS of the Power Profiler app to increase the sample duration's but I'm not confident enough to really try using it.

Thank you so much!

Cheers,

Devin

[Simonr]

Hi Devin

Due to the summer vacation period here in Norway we are short on staff and delayed replies must be expected. I'm sorry for any inconvenience this might cause.

This behavior seems strange indeed. First off, are you measuring in Source meter mode or Ampere meter mode? If you're in Source meter mode, make sure that the source output voltage is set to a value suitable for your device. Can you also provide some details on how exactly you go into "low power mode"? Are you going into System OFF mode, or in an idle system ON mode of some kind?

Depending on the sampling rate you'd like, you can increase the sample duration up to 500 days as explained in this YouTube video. We can't guarantee the behavior if you start modifying the JS yourself, but there shouldn't be any restrictions in the HW keeping you from setting this sample period yourself.

Best regards,

Simon

[DevinCallahan]

Hey Simon,

Thank you for the response!

Simonr said:

First off, are you measuring in Source meter mode or Ampere meter mode?

The PPK is configured as an ampere meter for this setup.

Simonr said:

Can you also provide some details on how exactly you go into "low power mode"?

The supply being measured in this instance is a 3V regulated supply that we use as VDD_GPIO for the nrf9160, as well as VCC for the other microcontrollers we have on our design.  The microcontroller turning on in this instance is an MSP430 which is being put into its low power mode.  That is done manually in its firmware and is indicated by the digital pin 7 going "low" in the capture.