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M
minded
Associate
April 17, 2025
Solved

Too high current draw in shutdown mode

  • April 17, 2025
  • 2 replies
  • 448 views

I'm just getting started with my STM32WB15CC nucleo board, and my first goal was to put in shutdown mode to check the current draw, which I expected to be around 1 uA. I'm measuring the current on the JP3 header with a joulescope which should represent the actual current used by the MCU itself.

I'm using the PWR_LPSLEEP example in the CubeMX IDE, and exchanged the "entersleepmode" call to the "enter shutdown mode", see below:

 

/* Enter Sleep Mode, wake up is done once User push-button (SW1) is pressed */

//HAL_PWR_EnterSLEEPMode(PWR_LOWPOWERREGULATOR_ON, PWR_SLEEPENTRY_WFI);

HAL_PWREx_EnterSHUTDOWNMode();

 

After the shutdown call, the joulescope shows a current draw of 42 uA, which seems very high for shutdown mode.

Am I missing something? Any pointers?

The reason I want to start with this basic test is because the project I'm working on is for a battery driven sensor, so a low current is crucial.

Best answer by minded

By examining and copying the code used in the STM32LowPower Arduino library from the STM32duino core, I found the issue. What was missing was to enter shutdown mode on the radio core of the STM32WB15CC:

 
LL_C2_PWR_SetPowerMode(LL_PWR_MODE_SHUTDOWN);

/**
* @brief Set Low-Power mode for CPU2
* @rmtoll C2CR1 LPMS LL_C2_PWR_SetPowerMode
* @PAram LowPowerMode This parameter can be one of the following values:
* @arg @ref LL_PWR_MODE_STOP0
* @arg @ref LL_PWR_MODE_STOP1
* @arg @ref LL_PWR_MODE_STOP2 (*)
* @arg @ref LL_PWR_MODE_STANDBY
* @arg @ref LL_PWR_MODE_SHUTDOWN
*
* (*) Not available on devices STM32WB15xx, STM32WB10xx, STM32WB1Mxx
* @retval None
*/
__STATIC_INLINE void LL_C2_PWR_SetPowerMode(uint32_t LowPowerMode)
{
 MODIFY_REG(PWR->C2CR1, PWR_C2CR1_LPMS, LowPowerMode);
}

Code formatting applied - please see How to insert source code for future reference.

2 replies

Andrew Neil
Andrew Neil
Super User
April 17, 2025

Make sure you've disconnected all connections to the ST-Link - leakage there could easily account for 40uA...

Check the schematics very carefully for any other possible leakage paths.

You may need to power cycle - not just reset - after using the debugger/programmer ...

A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
M
mindedAuthor
Associate
April 17, 2025

I'm using USB-C only, can I still disconnect ST-Link in that case, or is not needed then?

I also tried to put the device in shutdown from an application built with Arduino-IDE and the "low power" library. And this seems to work - I get about 1 uA current draw in shutdown.

M
mindedAuthorAnswer
Associate
April 17, 2025

By examining and copying the code used in the STM32LowPower Arduino library from the STM32duino core, I found the issue. What was missing was to enter shutdown mode on the radio core of the STM32WB15CC:

 
LL_C2_PWR_SetPowerMode(LL_PWR_MODE_SHUTDOWN);

/**
* @brief Set Low-Power mode for CPU2
* @rmtoll C2CR1 LPMS LL_C2_PWR_SetPowerMode
* @PAram LowPowerMode This parameter can be one of the following values:
* @arg @ref LL_PWR_MODE_STOP0
* @arg @ref LL_PWR_MODE_STOP1
* @arg @ref LL_PWR_MODE_STOP2 (*)
* @arg @ref LL_PWR_MODE_STANDBY
* @arg @ref LL_PWR_MODE_SHUTDOWN
*
* (*) Not available on devices STM32WB15xx, STM32WB10xx, STM32WB1Mxx
* @retval None
*/
__STATIC_INLINE void LL_C2_PWR_SetPowerMode(uint32_t LowPowerMode)
{
 MODIFY_REG(PWR->C2CR1, PWR_C2CR1_LPMS, LowPowerMode);
}

Code formatting applied - please see How to insert source code for future reference.

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