51802 debug mode consuming less power?

[Borden]

Hi community, I'm running a 51802 on my custom board with no other parts on it, except for some buttons and leds directly connected to GPIO, and a DC/DC converter which feed the 51802 with 1.8V power directly. I'm running a custom 2.4G protocol with neither softdevices, nor Gazell lib, which keep 16M clock always running.

Now when I try to optimize power, I've found some interesting thing that I can't find an explanation. I measure current before the DC/DC, so the absolute current read is not so relevant. The cpu is running the main loop steadily merely check for GPIO buttons, not much radio activities except sending a heartbeat packet every second,

the current read 2.21mA.

But if I reset the board to debug mode(with jlink plugged),

the current read 0.96mA.

I've checked this many times to make sure, as long as power is on, the consumption keeps the low state, and there seems no difference of the functionality of the 51802.

So my question is: why in debug mode, the power consumption reduced to about 44% of the normal state? what's changed inside the chip?

[Borden]

nrf51422_xxac.hex

Hi Sigurd, here's the hex file for you to test, it works with S130v2.0.1, thanks!

[Sigurd]

Hi,

I have now tested the hex you uploaded on a nRF51-DK.

I measure 1.56 mA in regular mode, and 2.3mA in debug mode. After 30 seconds I get a Advertising timeout event, and the current goes up to 4.6 mA. This could be an issue with entering system OFF mode.

Could it be that you are measuring the current from other components on your board? Have you tried testing with 3 Volt?

Note that since you are running the chip in low voltage mode(under 2 Volt), DEC2 shall be connected to VDD. Have you done this on your custom board?

[Borden]

Yes I've connected DEC2 to 1.8V, I've checked just now. Were you testing my firmware on 51822 or 51802? Your readings looks far from mine. I've connected the power LED to P26(pin 45), and the power button to P09(pin 15), which I've forgotten to tell you, sorry. You may check it again with this LED and button, if it's not too bother for you.

[Sigurd]

I tested using a 51822/51422. How should the P26 and P09 be connected ?

Have you tried removing the DC-DC, and running your 51802 at 3V ?

[Borden]

I haven't test it on a 3V config or other than 51802 because this board is currently is the only one I'm working on.

The LED pin output low when LED should be on, or disconnected when LED should be off. The button pin is a internally pull-up inpiut, a button simply connect to GND and this pin will work.

Maybe 51802 act differently from 51822? or maybe the debug module act differently under external 1.8V?

[Sigurd]

Hi Borden,

I have now tested on a 51802, but it act the same as the 51822. The 51802 uses abit more current overall than the 51822, but the 51802 also uses more current in debug mode than in normal mode for me. Actaully for me it uses 1.6 mA more in debug mode.

Are you sure that the chip is actually working when you have it debug mode? is the debug mode interfering with any other components on your board? Are you using a original/legal(non-copy) debugger?

You could also ask for a design review in mypage. Remember to upload all schematics and geber files.