GPIO state for the lowest consumption of STM32L052 in STOP mode

[ivan239955_stm1_stmicro_com]

Posted on November 05, 2015 at 10:40

I am going to use STM32L052 in STOP mode (LSE RTC running, RAM data keeping, both RTC and EXT pin wake-up).

1.

I know that for the lowest consumption GPIOs should be set as Analog.

What I do not know:

Should pins be connected to external pull-up or pull-down resistors to set VDD or VSS?

Can any leakage from external circuits that sets a voltage on them (without pull resistors) make the consumption worse?

2.

Does Input Floating mode with either internal or external pull-downs/pull-ups cause worse consumption?

3.

Does Output Push-pull mode (of course WITHOUT any external circuit allowing current flow) cause worse consumption?

Thank you for any information.

#stm32l0-consumption-stop

[Danish1]

Posted on November 05, 2015 at 12:17

The reason why you would set pins as analog to save current is to disable the digital input circuit.

The digital input circuit (which you can think of as a simple inverter) only draws current (from the power-supply) when a pin is somewhere between Vdd and Vss, and if you have left the pin floating then it could easily float to such a voltage.

But if your external circuit causes the pin to be at Vdd or Vss then there is no major saving by setting the pin as analog.

Equally if you drive the pin as a digital output either high or low, or pulled-up/down (and your external circuit does not cause current to flow into/out of the pin when in that state) then this should be just as good.

Hope this helps,

Danish