How to measure current on board PCA10056

[Beike]

Board：PCA10056 （0.9.3）

SDK：15.2

Softdevice：S140

Example：ble_app_blinky

Today，I follow this page Using an ampere-meter for current measurement to measure the current,

And follow this page Preparing the development kit board to prepare the board,

And follow this page nRF52840 direct supply to support external power.
so, the connection mode is this:

1. External 3.3V power connected to P21

2.Connect an ampere-meter between the pins of connector P22
3.SW10 is on; SW8 is VDD; SW6 is nRF ONLY

4.SB40 has been cutted

Now, I can scan its adv by my Nordic connect app.but, the current is 7.x mA, it's so high, can you tell me why?my connection mode is wrong?

[Andreas]

Hi,

 

This sounds a little high, have you modified the example in any way?

 

Best regards,

Andreas

[Beike]

Thanks for your reply,

Yes, I find it has been changed.so, I programmed with The original procedure.

And now, the current is 1.6mA when it's advertising, 1.35mA when it's connected with phone.

so, I have a few questions:

1. Is the method of measuring current correct?

2. The current 1.35mA when advertising, is it normal? How much it should be?

3. According to the reference manual, the current should be 1.x uA, it's Right?

    If so, how can I reduce current from 1.35 mA to 1.x uA?

[Andreas]

Hi,

 

OK, if you have changed the example it is not possible for me to judge if the current consumption is correct or not.

When advertising and in a connection, the nRF52840 switches the radio on and off, between TX and RX, and uses CPU and other peripherals depending on what your application tells the Softdevice and the HW. Radio on is typically when the instantaneous current consumption is highest, so with a larger ratio of time the radio is on, the average current consumption will increase. This is mainly affected by advertising/connection intervals and packet length, shorter intervals and longer packets mean higher current consumption.

Your setup should be correct from what I can see. 1.3-1.6 mA is plausible, but as mentioned it depends on what intervals and packet settings you have configured.

1.x µA is typically the system ON current, sleep current between the radio events. Achieving this as average current consumption is strictly not possible if you want to do anything besides sleeping, but obviously average current consumption will approach this value as the intervals increase.

 

I suggest that you take a look at our power profiler calculator: https://devzone.nordicsemi.com/power Set up the same settings as in your application and compare it with what the calculator spits out. If you do not know your settings, narrowing down that would have to be done first, it is hard to judge power consumption if not.

 

Also keep in mind that your board (v0.9.3) has an engineering A revision SoC on it. This is an unfinished device, as such current consumption in the production revision (v1.0.0) might be different because of improvements, optimizations and bug fixes.

 

Best regards,

Andreas

[Beike]

Thanks for you reply,

If there is no problem with the current measurement method, then I think it may be the PCA10056 hardware problem.

I program the same hex to my custom board, the current is 14uA when it's advertising (1S advertising interval). 

About the custom board:

1. It is just a MCU and a SWD interface

2. use external 32k Crystal oscillator

3. Use RTC1  as the app timer.

4. SYSTEM ON mode and low power sub-mode

5. advertising interval is 1S, I think it's enough to measure the current

I use power profiler calculator to calculate the current of custom board, it shows the IDLE current should be 2.5uA.

So, the anther question is what would cause the current to be 14 uA instead of 2.5 uA? 

[Andreas]

Hi,

 

You are comparing apples and bananas. Your ampere-meter is measuring total average current (not similar to idle current) but comparing with idle current (not similar to average current).

Idle current is the instantaneous current consumption (sleep current) when the SoC is asleep between the advertising events, while average current is the average current consumption over the advertising event and the idle period before the next advertising event (1s). As the current consumption during the advertising event is higher than the sleep current, the total average current will be different and higher than the sleep current.

 

Best regards,

Andreas

[Beike]

OK，I see what you mean。I may need to change my measurement Tool.

Thanks.