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STM32U5 - achieving low power (micro ampere range)

_Danny_
Associate III

Hi,
We are currently utilizing a custom-designed STM32U5G7 microcontroller for our application with the MSI clock configured to 1 MHz. Despite configuring the device in Sleep and Stop modes, with all GPIO pins set to input and one pin configured as an EXTI interrupt for wake-up, we are observing a current draw of approximately 2mA. Our goal is to reduce the current consumption to the micro ampere range. Could you provide guidance on further optimizing power management and implementing lower-power modes?

I have attached the code ,pin out configuration and current drawn  measured using Otii.

_Danny__0-1743056824480.png

_Danny__1-1743056858029.png

_Danny__2-1743056957591.png

/* USER CODE BEGIN Header */ /** ****************************************************************************** * @file : main.c * @brief : Main program body ****************************************************************************** * @attention * * Copyright (c) 2025 STMicroelectronics. * All rights reserved. * * This software is licensed under terms that can be found in the LICENSE file * in the root directory of this software component. * If no LICENSE file comes with this software, it is provided AS-IS. * ****************************************************************************** */ /* USER CODE END Header */ /* Includes ------------------------------------------------------------------*/ #include "main.h" #include "memorymap.h" #include "gpio.h" /* Private includes ----------------------------------------------------------*/ /* USER CODE BEGIN Includes */ /* USER CODE END Includes */ /* Private typedef -----------------------------------------------------------*/ /* USER CODE BEGIN PTD */ /* USER CODE END PTD */ /* Private define ------------------------------------------------------------*/ /* USER CODE BEGIN PD */ /* USER CODE END PD */ /* Private macro -------------------------------------------------------------*/ /* USER CODE BEGIN PM */ /* USER CODE END PM */ /* Private variables ---------------------------------------------------------*/ /* USER CODE BEGIN PV */ volatile uint8_t wakeUpFlag = 0; /* USER CODE END PV */ /* Private function prototypes -----------------------------------------------*/ void SystemClock_Config(void); /* USER CODE BEGIN PFP */ /* USER CODE END PFP */ /* Private user code ---------------------------------------------------------*/ /* USER CODE BEGIN 0 */ void SleepMode() { HAL_SuspendTick(); HAL_PWR_EnterSLEEPMode(PWR_MAINREGULATOR_ON, PWR_SLEEPENTRY_WFI); HAL_ResumeTick(); } /* USER CODE END 0 */ /** * @brief The application entry point. * @retval int */ int main(void) { /* USER CODE BEGIN 1 */ /* USER CODE END 1 */ /* MCU Configuration--------------------------------------------------------*/ /* Reset of all peripherals, Initializes the Flash interface and the Systick. */ HAL_Init(); /* USER CODE BEGIN Init */ /* USER CODE END Init */ /* Configure the system clock */ SystemClock_Config(); /* USER CODE BEGIN SysInit */ /* USER CODE END SysInit */ /* Initialize all configured peripherals */ MX_GPIO_Init(); /* USER CODE BEGIN 2 */ SleepMode(); /* USER CODE END 2 */ /* Infinite loop */ /* USER CODE BEGIN WHILE */ while (1) { /* USER CODE END WHILE */ /* USER CODE BEGIN 3 */ } /* USER CODE END 3 */ } /** * @brief System Clock Configuration * @retval None */ void SystemClock_Config(void) { RCC_OscInitTypeDef RCC_OscInitStruct = {0}; RCC_ClkInitTypeDef RCC_ClkInitStruct = {0}; /** Configure the main internal regulator output voltage */ if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE4) != HAL_OK) { Error_Handler(); } /** Initializes the CPU, AHB and APB buses clocks */ RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI; RCC_OscInitStruct.MSIState = RCC_MSI_ON; RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT; RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_4; RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE; if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) { Error_Handler(); } /** Initializes the CPU, AHB and APB buses clocks */ RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2 |RCC_CLOCKTYPE_PCLK3; RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI; RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV4; RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1; RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1; RCC_ClkInitStruct.APB3CLKDivider = RCC_HCLK_DIV1; if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK) { Error_Handler(); } } /* USER CODE BEGIN 4 */ /* USER CODE END 4 */ /** * @brief This function is executed in case of error occurrence. * @retval None */ void Error_Handler(void) { /* USER CODE BEGIN Error_Handler_Debug */ /* User can add his own implementation to report the HAL error return state */ __disable_irq(); while (1) { } /* USER CODE END Error_Handler_Debug */ } #ifdef USE_FULL_ASSERT /** * @brief Reports the name of the source file and the source line number * where the assert_param error has occurred. * file: pointer to the source file name * line: assert_param error line source number * @retval None */ void assert_failed(uint8_t *file, uint32_t line) { /* USER CODE BEGIN 6 */ /* User can add his own implementation to report the file name and line number, ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */ /* USER CODE END 6 */ } #endif /* USE_FULL_ASSERT */
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Edit: code formatting

2 REPLIES 2
Amel NASRI
ST Employee

Hi @_Danny_ ,

To optimize power consumption, it is recommended to configure unused pins in analog mode (instead of input floating).

To do it with STM32CubeMX, please follow this article: How to minimize the power consumption in low power mode: An example using NUCLEO-F401RE board.

Please try and let me know if there is any difference.

-Amel

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.


@_Danny_ wrote:

a custom-designed STM32U5G7 microcontroller


You mean a custom-designed board ?

Please provide the schematic of the board.

 


@_Danny_ wrote:

we are observing a current draw of approximately 2mA.


How, exactly, are you observing that?

 

You will need to physically disconnect any debugger to see true low-power operation.

You may also need a power-cycle (not just a reset) after disconnecting a debugger.

 

Presentation on STM32U5 Power management:

https://www.st.com/content/ccc/resource/training/technical/product_training/group1/95/38/81/9b/cb/0d/43/89/STM32U5-System-Power-management_PWRMNGMNT/files/STM32U5-System-Power-management_PWRMNGMNT.pdf/_jcr_content/translations/en.STM32U5-System-Power-management_PWRMNGMNT.pdf

 

Other resources:

https://wiki.stmicroelectronics.cn/stm32mcu/wiki/Getting_started_with_LPBAM

https://www.youtube.com/watch?v=fm-IcVh5WI0

https://wiki.stmicroelectronics.cn/stm32mcu/wiki/Introduction_to_Low_power_with_STM32

https://www.st.com/en/microcontrollers-microprocessors/stm32u5f7-5g7/documentation.html - search for "power"

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.