Why is power consumption so high in system off? (not debug)

[syntroniks]

I am aware that the debugging interface draws significant current, I do not believe that is the case.

I have 2 designs in front of me. Let's call them '2.0' and '3.3' (their HW revision #s). Both are machine assembled. I am running the SDK's 'ble_app_template' program modified as shown below:

/**@brief Function for application main entry.
 */
int main(void)
{
  int i = 0;
  for (i = 0; i < 10000; i++)
  {
  	
  }
  NRF_POWER->SYSTEMOFF = 1;
		
// Initialize
leds_init();
timers_init();
gpiote_init();
buttons_init();
ble_stack_init();
...

You will see that after a short delay I enter system off. '2.0' is a nRF51822-QFAB A0 programmed with S110 5.x, '3.3' is a nRF51822-QFAB B0 programmed with S110 6.0.0

I load this code onto both designs. On '2.0' I measure 1.2 microamperes of supply current @ 3.0 volts. On '3.3' I measure ~470 microamperes at 3.0 volts.

Since we all know '2.0' is fine I will not attach design documents. The significant difference is the silicon revision and it is using the STM balun.

I've attached a screenshot of the schematic. (the site notes that I must have 10 points to upload files, please give me some points :))

Update: Through removing/reworking various components I am growing more and more confident that this is an issue with my circuit board assembly. Will update when the culprit is found.

[Håkon Alseth]

That is a very strange measured current consumption. Your program basically goes straight into systemoff, so that should be fine. Do you see this issue on more than one rev3.3 board? Just to verify that this is not a solder/PCB issue.

[syntroniks]

The issue was a 12K pullup on SWDCLK. I am not certain why it causes excessive power draw (a bit more than ohm's law would predict) but removing that part solves everything. I'll add the answer to this question and accept it. (wish we could post pictures!)

[Håkon Alseth]

Glad to hear that you found the issue. Note that the resistor on SWDCLK should be a pull-down, not pull up. On the first revision of the nRF51x22, this pull-down was missing internally, but that was fixed on the second revision.

The 10 point thing is a bit strange, I will request that this is removed so that new users can post images and attachments.