Power consumption of the Nucleo 64 board : STM32L073ZR.

[SBour.9]

Hi everyone!

I am trying to get the lowest power consumption from the STM32L073ZR in STOP Mode.

I run my tests with the board powered from external source E5V (no USB connected).

I have two Ampere-meters:

• one measure the current IDD of the microcontroller (JP6)
• the other measure the overall consumption of the board

I get IDD = 0.3 uA (so i enter the STOP Mode correctly). However i measure 50 mA for the total current.

Do someone knows where the 50 mA come from and how to reduce it?

Nb: I didn't touch any solder bridge yet.

[SBour.9]

A solution could be to powered directly with 3.3 V with the solder bridge 2 and 12 OFF. Thus the STLink, the two regulators and the LED3 are not powered so it should decrease the consumption. (cf User manual UM1724 chapter 6.3.3). Is it still possible to program the MCU with STLink powered from USB with this config?

I am still looking for a low power solution with a 5V power supply.

LED3 (or R32) can be remove to save few mA but i cannot find an easy way to disconnect the STLink (maybe removing D3 but it doesn't look like a clean solution and might create other problems)

[SBour.9]

I tested the solution this external power supply 3V3. (programming with STLink doesn't seem possible in this configuration [SB12 OFF] ).

With the same ampermeters I get IDD = 0.6 uA (I don't know why it doubles up). And i measure 0.40 mA for the total current. It is much better than the 50 mA but there is still 400uA going somewhere.

The only current path going from 3V3 and not passing though JP6 i can find is one:

I measure 1.9 V at R23. It gives a current of 400uA. Since i don't need STLink, maybe i could remove R23 and thus delete those 400uA?

[SBour.9]

Apparently there is an other solution: power the MCU from the Arduino AREF pin (=AVDD). This configuration allows the MCU supply to be isolated from peripherals (ST-LINK).

The solution is describe in UM2243 chapter 15.2 (but nothing on this in the Nucleo 64 user manual)

However I don't understand why is it necessary to open all the ST-Link solder bridge (SB 12 => SB16) since the ST-Link is not powered in this configuration ?

[SBour.9]

UM2269: "– Remove solder bridge SB12 to disconnect reset signal from ST-Link part (ST-Link can still be used with this configuration to load and debug a program, software tool option “Connect during reset�? may be needed)."

=> Could be the solution to program with SB12 open (i haven't try yet)

[SBour.9]

UM2269 chapter 1.2 says that only SB12 have to be open (and JP6), seems more legit to me.