Over consumption on the SAAC

[Mehdi GHARBI]

Hi,

I use the SAADC with the NRF52832. 

This is the schematic used :

When we use AN_IN (TOR_IN 1 and TOR_IN 2 are not used), only the components assigned to AN_IN are mounted on the board. The consumption increase when we put a voltage on T20 (input P0.03=> D6 on the WLCSP ball assignments) from an external power supply. We d'ont use the internal pull-down or pull-up on P0.03. 

Example for various voltages on the PIN T20:

• 106µA when i put 3V
• 61.62µA for 2.5V
• 5.19µA for 1.5V
• 380nA for 1V

Can you help to understand this over consumption please?

Best regards,

Mehdi GHARBI Ingénieur Électronique  /  Electronic Engineer

[Stian Røed Hafskjold]

Can you try to cut the trace close to P0.03 and supply voltage to the pin directly? It's not clear to me if the current is flowing into the chip or through any of the external components.

Can you please post the complete ADC initialization code? Thanks

Can you also try to init the ADC to use another pin, and supply voltage to this pin? I've seen similar excessive current that increases with voltage if the ESD diodes on the GPIO are damaged.

[Mehdi GHARBI]

We found the problem. The pin P0.03 is floating so when i apply a potential, the GPIO is in state unknown and the consomption increases. Now the pin is like Analog input => see pin configuration below :