nRF52832 current consumption

RE: nRF52832 current consumption

RK — Fri, 20 Nov 2015 12:59:22 GMT

If you disable radio and still measure 12.9mA then you should suspect your method of measurement more than anything else.

You really can't treat the AC current reading from an inexpensive, non-RMS meter, with a minimum current range 5x greater than the average RMS current you're trying to measure, applied to an occasional short pulse of activity at a frequency much higher than the range that meter is designed to measure, as anything much more than a random number.

If you really want to measure a tiny average current like that with any sort of accuracy at all, you need much better equipment.

RE: nRF52832 current consumption

Juba Belgaid — Fri, 20 Nov 2015 10:41:35 GMT

if i disable radio in the main function, i measure 12.9mA

RE: nRF52832 current consumption

Øyvind Karlsen — Fri, 20 Nov 2015 10:26:34 GMT

Hi,

From the specification of your ampere meter you can see that it only measures down to 200µA minimum. This is also for 45 to 500 Hz range, which is too slow to be able to see the spikes that come from the radio being active. The radio sends advertising packets every 100ms in the base example, 100ms corresponds to 10Hz. What probably happens in your ampere meter is that it will sample the current drain in such a way that it will seem that the radio is always on.

RE: nRF52832 current consumption

Juba Belgaid — Fri, 20 Nov 2015 10:06:56 GMT

www.amprobe.com/.../amp-5xp-a.htm

RE: nRF52832 current consumption

Øyvind Karlsen — Fri, 20 Nov 2015 10:03:10 GMT

Which ampere meter are you using?

RE: nRF52832 current consumption

Juba Belgaid — Fri, 20 Nov 2015 09:45:50 GMT

i am using the original code.

RE: nRF52832 current consumption

Øyvind Karlsen — Fri, 20 Nov 2015 09:39:49 GMT

If you are using the beacon example then the radio will be active, unless you have modified the code?

RE: nRF52832 current consumption

Juba Belgaid — Fri, 20 Nov 2015 09:36:48 GMT

Hi,

Thank you for reply, i measure 9.7 mA every time (radio active or not).

best regards

RE: nRF52832 current consumption

Øyvind Karlsen — Fri, 20 Nov 2015 07:35:49 GMT

Hi,

What you are measuring is the current that is being drained while the radio is active. This current will be significantly higher, but will only occur parts of the time. The resolution of your ampere meter is likely not good enough to be able to detect that these are peaks, so you will get a slew of measurement errors.

Best regards,

Øyvind

RE: nRF52832 current consumption

Juba Belgaid — Thu, 19 Nov 2015 15:25:21 GMT

Hello,

I use the preview kit pca10036, i programm it with ble_app_beacon example. I measure a consumption of 9.7 mA !! (by connecting an ampere-meter between the pins of connector P22).

You announce a consumption of nRF52 DK 2 - 39µA !!!!

So there is a big difference, To what this could be due ?

Thanks

RE: nRF52832 current consumption

Øyvind Karlsen — Tue, 07 Jul 2015 07:04:04 GMT

Hi,

I used a 150µF cap across the exit, you can use a larger value as well, I didn't try with lower values. This smoothed out the peaks somewhat for me, so you might be fine with your multimeter.

RE: nRF52832 current consumption

mikaelbdl — Mon, 06 Jul 2015 21:46:00 GMT

Hi Øyvind,

Thanks for the detailed reply.

I’ll admit the 34450A multimeter is not the best instrument for the job. I had been using this for relative comparisons between nRF51 firmware setups hoping that 190 Hz sampling would be enough to get reasonable comparisons without the need of an amplifier/oscilloscope, or power analyser. It sounds like this assumption well and truly falls over when comparing nRF51 to nRF52 so I will address this more carefully.

Do you have detail on capacitor bank sizing and attachment?

I have a low cost 80 kHz current amplifier on order that may mimic performance of your power analyser more closely. I will attempt to retest using this and capacitor bank averaging when I get the chance.

Kind Regards,

Mikael

RE: nRF52832 current consumption

Øyvind Karlsen — Mon, 06 Jul 2015 11:33:07 GMT

Hi,

First off, sorry for the late answer, this proved to be more difficult than first thought.

I've done measurements now, this is my setup:

Keysight N6705B DC Power Analyzer
Keysight E3646A DC Power supply
nRF 51 DK
2x nRF 52 DK
nRF 52 Testbench

This testbench is the reference layout for the nRF52 as well as a small sensor circuit that draws current in the ~200nA range. It also has a capacitor bank for measurements, more on that later. I used the E3646A power supply to provide 3V with a current draw limitation of 12mA.

For the measurements before enabling DCDC-mode my results in the idle state were:

nRF51 DK - 3,23µA
nRF52 DK 1 - 9,24µA
nRF52 DK 2 - 39µA
nRF52 Testbench - 1,8µA

These results may seem a little odd, however it is the result for the testbench that is valid.

First there's the error that stems from the high dynamic range between current draw for TX mode and idle mode. Essentially this will make fluctuations in the idle state invisible to our measuring equipment. This will lead to an error in our measurements, but it will not be the main contributor.

The nRF52 has a power supply that will rapidly charge a capacitor at a voltage threshold, this causes high frequency "spikes" in the current drawn. These spikes are so high frequency that most measuring equipment is not able to measure them accurately, in fact aliasing will occur and you will see values that are incorrect. This is where the large values and variations likely stem from. To circumvent this issue and the high dynamic range issue a capacitor bank is added to smooth out our measurements, this allows us to get stable readings. We're working to address this issue, stay tuned for more information.

Also note that the leakage current from the preview DK will be larger than those for the testbench, due to a higher amount of components which lead to a higher chance of error.

For the DCDC-mode these were my results:

nRF 51 DK - 3,25µA
nRF 52 DK 1 - ~220µA
nRF 52 DK 2 - ~220µA
nRF52 Testbench - ~220µA

This is where we probably encounter the error from the errata, further testing shows that this is 220µA current draw will disappear when adjusting voltage. We're also working on this issue, so again, stay tuned for more information.

Best regards,

Øyvind

RE: nRF52832 current consumption

mikaelbdl — Wed, 01 Jul 2015 02:47:28 GMT

I've attached the Keil projects. Only modifications from provided examples are to main.c. To compare devices for issue 2 you can un-comment DCDC mode set line in main().

RE: nRF52832 current consumption

Øyvind Karlsen — Tue, 30 Jun 2015 06:07:10 GMT

Hi,

It is possible that that issue is related, if you provide some code, I will attempt to replicate your results.

Best regards,

Øyvind

RE: nRF52832 current consumption

mikaelbdl — Mon, 29 Jun 2015 02:20:01 GMT

Just overlooked this. Could it be related? infocenter.nordicsemi.com/index.jsp