measure true current consumption on STM32 B-L072Z-LRWAN1 in Sleep Mode?

[Mariiian09]

I’m testing low-power modes on my STM32 B-L072Z-LRWAN1 board and measuring the current consumption.

When I measure the current using a Xiao PowerBread, I get around 20 mA on the 5 V rail, even when the MCU enters Sleep Mode.

My question is whether the on-board LEDs (LD5 and LD7) could be masking the expected drop in power consumption.

According to the board documentation:

• LD7 (Red) is the 5 V Power LED, which is always on when 5 V is present.

• LD5 (Green) is the ST-LINK COM LED, powered from the ST-LINK interface and active during communication.

Since these LEDs are powered from the 5 V rail and the ST-LINK section, they remain on regardless of the MCU power mode.

So my questions are:

1. Can these LEDs (and the ST-LINK interface) prevent me from seeing the real power drop when the MCU goes into Sleep Mode?

2. What is the best way to measure only the MCU’s current consumption, excluding the ST-LINK and LEDs?
   Should I remove some jumpers or power the MCU directly through the VIN V pin?   
   
   Thanks in advance.

[Andrew Neil]

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@Mariiian09 wrote:

1. Can these LEDs (and the ST-LINK interface) prevent me from seeing the real power drop when the MCU goes into Sleep Mode?

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Absolutely!

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@Mariiian09 wrote:

2. What is the best way to measure only the MCU’s current consumption

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That's what the 3 current measurement links are for.

But even then there are still some hidden current drains:

Excess Current Consumption Running B-L072Z-LRWAN1 From Battery??