Confusion with online power profiler.

[GLNeedham]

Hi, We are developing a product based on the nRF52832 and have been measuring the current consumption on our first prototypes with a Keysight N6705 power analyser. We seem to have a base current, when the CPU is sleeping of around 100uA which was higher than we expected.

By way of confirmation I used the Online Power profiler to get an idea of what to expect and it suggests a standby current of 200uA might be expected

This seems really high to me?

Also if I select the option to turn the DCDC on the standby current increases - also very unexpected?

Can anyone explain why the current profiler indicates such a high standby current? I would have expected it to be in the single digit microamps!!

By way of additional information our FW has UART logging turned off, the App uses the RTC to wake up every 100ms or so to do some work and we are running the LFOSC from a 32KHz Xtal.

May be I am missing something?

Many thanks

[Simonr]

Hi Glenn

This standby current you're seeing in the online power profiler is the standby current before the radio turns on, where the HFCLK is running (consuming ~200µA). The sleep current should not be as much as 100µA either like what you're seeing on your device. I assume you have a peripheral still running that is drawing this extra current, as an nRF52832 in sleep mode running the RTC in sleep mode shouldn't consume more than ~2.6µA. Please see this table for more information on the sleep mode currents (yes this is from the nRF52833 PS, as we haven't updated the nRF52832 PS to include these current consumption scenarios, but they are very similar in terms of current consumption).

Can you show me a snippet of how your application goes to sleep and initializes the RTC? If you're seeing the total current consumption being ~100µA that might be because of what the application does every 100ms when it "wakes up to do some work". Are you able to measure the current consumption in specific parts of the application running, I.E. just when operating and just when it's asleep?

Please note that we're entering the summer vacation period here in Norway, so delays must be expected as we are low on staff for the month of July. Sorry about the inconvenience!

Best regards,

Simon

[GLNeedham]

Simon,

Our FW is based on your template:

C:\Nordic SDK\nRF5_SDK_15.3.0_59ac345\examples\ble_peripheral\ble_app_template

and we have not modified the power management code at all.

Using the Keysight power analyser I can examine the current consumption at any moment in time and the 100uA current is the instantaneous current between advertising and between our 100ms wake up so it is at the time when the CPU should be asleep.

What I can say is that we have 'inited' SPI, RTC, I2C and PWM but while asleep they are not active therefore I suspect that the current being consumed is the IDLE current for each of these peripherals. We do not call the uninit functions because we need to maintain the pin states.

I don't think the HF OSC can be running as the current is not high enough for that (datasheet says 250uA typ.)

Perhaps just the SPI and I2C block current is accounting for what we see?

Regards

Glenn