NUCLEO-U575ZI-Q excessive current consumption

[Dadigno]

I'm using the NUCLEO-U575ZI-Q board with the PWR_ModeSelection example, and I'm measuring the current consumption with an ammeter through the JP5 (IDD) connector.

The current I measure in the different low power modes is always around 4.52 mA, which does not match the values stated in the datasheet.

I'm probably making a configuration mistake. To use the example, I followed the README included in the SDK.
As toolchain, I'm using CMake and VSCode as the IDE.

Where am I going wrong?

[Andrew Neil]

To measure really low power modes, you need to ensure that all sources of current leakage are disconnected - in particular, the ST-Link.

Unfortunately, the NUCLEO-U575ZI-Q  doesn't have the break-off ST-Link section - which is the easiest way to do that.

So you will have to thoroughly study both the User Manual and the schematics, and make all the required disconnections.

Note that just the User Manual may not be sufficient; eg, see:

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

 

The User Manual can be found on the 'Documentation' tab of the board's Product Page:

https://www.st.com/en/evaluation-tools/nucleo-u575zi-q.html#documentation

The Schematics should be available on the 'CAD Resources' tab:

https://www.st.com/en/evaluation-tools/nucleo-u575zi-q.html#cad-resources

 

#NucleoLowPower #LowPower

[Dadigno]

@Andrew Neil 

I tested the PWR_EnterStopMode firmware, but the current consumption didn’t go below 500 µA.
So I modified the example code by disabling the SysTick,

 /* Switch OFF LED1 */
 LED_Off();

 SysTick->CTRL &= ~SysTick_CTRL_ENABLE_Msk;

 /* Enter STOP 0 mode */
 EnterSTOP0Mode();

Then I changed the EnterSTOP0Mode function to call LL_PWR_SetPowerMode(LL_PWR_STOP2_MODE) since STOP2 mode is the one I’m interested in.

void EnterSTOP0Mode(void)
{
 /** Request to enter STOP 0 mode
 * Following procedure describe in STM32U5xx Reference Manual
 * See PWR part, section Low-power modes, STOP 0 mode
 */
 /* Set STOP 0 mode when CPU enters deepsleep */
 LL_PWR_SetPowerMode(LL_PWR_STOP2_MODE);

 /* Set SLEEPDEEP bit of Cortex System Control Register */
 LL_LPM_EnableDeepSleep();

 /* Request Wait For Interrupt */
 __WFI();
}

 

Now the current drops to around 10 µA, which is still too high compared to the ~3.9 µA stated in the datasheet.

Configuration:

• SRAM2 page1 & page2 and ICACHE retained
• RTC disabled
• Power supply via JP5 using STLINK-PWR 3.3 V
  
  

I think it’s the same issue I mentioned in my other post, where I’m using a custom board with an STM32U595 MCU

https://community.st.com/t5/stm32-mcus-products/unexpected-current-consumption-in-stop2-mode-on-stm32u595/m-p/847317#M287272 

[Andrew Neil]

Yes, you will need to disable SysTick - otherwise it will keep waking the CPU!

 

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@Dadigno wrote:

Now the current drops to around 10 µA, which is still too high compared to the ~3.9 µA stated in the datasheet. 

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So you're chasing ~ 6 µA.

At this level, you have to be really careful about all possible sources of leakage - capacitors can become significant!

Have you carefully checked the schematics?

Are you sure that the ST-Link is completely disconnected?