NRF52 DK: ~60uA extra current draw when changing P0.27 to input!?

Question

Hello, 
 I'm using an NRF52 DK board. 
 I noticed that when I change P0.27 from the default (input / not connected to input buffer) to being an input pin connected to the input buffer, the current draw increases by ~60uA: 
 ``` 
 nrf_gpio_cfg_input(27, NRF_GPIO_PIN_NOPULL); ``` 
 If I comment out that line above, the current drops back by ~60uA.... 
 I'm also using P0.8 and P0.28-P0.31 as inputs, but not seeing the problem with those pins. 
 What could be the problem? 
 
 Note (probably not relevant, but mentioning for completeness): 
 I've shorted SB-4 and SB-3 and cut SB-1 and SB-2 and am using the internal RC oscillator for LF clock.

hmolesworth · Accepted Answer

Hmm, edited as I see the upper schottky clamp only apples to channel 1, not the 3 data channels. That only affects P0.17. 
 " should disconnect P0.26/P0.27 from the I2C pull-ups (R29 and R30) " .. ah, if only life were that simple. R29 and R30 can be clamped by internal schottky protection diodes within U7 as power switch voltage on the switch IC can rise above (VEXT+500mV) via (say) R29+R32 in series; if VEXT is Gnd that limits those voltages to 500mV-ish and allows current to flow between all those pins. To verify whether this is the root cause requires removing (say) R29 and checking the current draw again. 
 Also note P0.17 can possibly power up VEXT if driven high by the 0.5V schottky internal clamp on the NX3DV2567 switch itself. Perhaps start by ensuring P0.17 is floating or actively driven low (see edit note above).

hmolesworth · Answer

This is perhaps covered in the nRF52832 Development Kit v1.1.x User Guide v1.2 - see Table 5: pins P0.26 and P0.27 are used as i2c pins and have 4k7 pull-up resistors. This will introduce leakage into the input buffer when connected.

NRF52 DK: ~60uA extra current draw when changing P0.27 to input!?

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