STM32 standby mode power consumption is too high

Question

I'm experimenting with standby mode on STM32F407VGT6. I know how to put MCU into standby mode(or I think to know that). I'm doing that with this init function:

void MX_RTC_Init(void) {

   RTC_TimeTypeDef sTime = {0};  
   RTC_DateTypeDef sDate = {0};

   /** Initialize RTC Only  */   hrtc.Instance = RTC;  
   hrtc.Init.HourFormat = RTC_HOURFORMAT_24;  
   hrtc.Init.AsynchPrediv =127; 
   hrtc.Init.SynchPrediv = 255; 
   hrtc.Init.OutPut = RTC_OUTPUT_WAKEUP; 
   hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH; 
   hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN; 
   if (HAL_RTC_Init(&hrtc) != HAL_OK)   {
      Error_Handler();
   }

   /** Initialize RTC and set the Time and Date */
   sTime.Hours = 0x13;
   sTime.Minutes = 0x20;
   sTime.Seconds = 0x0;
   sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
   sTime.StoreOperation = RTC_STOREOPERATION_RESET;
   if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BCD) != HAL_OK)
   {
      Error_Handler();
   }
   sDate.WeekDay = RTC_WEEKDAY_THURSDAY;
   sDate.Month = RTC_MONTH_JANUARY;
   sDate.Date = 0x30;
   sDate.Year = 0x20;

   if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BCD) != HAL_OK)
   {
      Error_Handler();
   }
   HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1);

}

This init function allows to wake up MCU from standby mode with wakeup pin(PA0) and with timer(currently period is ~20sec). Next function is called when I want to put MCU into standby mode:

void Enter_StandbyMode(void)
{   
    __HAL_RTC_WAKEUPTIMER_CLEAR_FLAG(&hrtc, RTC_FLAG_WUTF);

    HAL_PWR_DisableWakeUpPin(PWR_WAKEUP_PIN1);
    __HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);
    HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1);

    HAL_RTCEx_SetWakeUpTimer_IT(&hrtc, 40960,RTC_WAKEUPCLOCK_RTCCLK_DIV16);

    HAL_PWR_EnterSTANDBYMode();

}

Again this works as I expect(I used diode to indicate when MCU wake-up from standby) but my question is next one:

Why I still have voltage on pins when MCU is in standby mode? And when I use multimeter to measure current I got ~30mA power consumption in normal mode(when MCU isn't in standby mode) and ~0.58mA(which is ~580uA) when MCU is in standby mode. I read in datasheet that MCU in standby mode can have power consumption less then 5uA. Every hint and idea are welcome

Answer 1

Have you enabled the Clock for the Power Module? It is kind of confusing that you have to enable something to reduce the power consumption.

Deactivating all clocks of unused Peripherals will also lead to a major power reduction. We also measure higher current consumption while the controller is still connected to a debugger.

Answer 2

Hopefully it isn't too late to answer this. You should configure all unused GPIO pins to GPIO_MODE_ANALOG and GPIO_NOPULL. If you need GPIO output pins configured on the STM32, you should use the lowest GPIO frequency speed, preferably GPIO_SPEED_FREQ_LOW.

Reducing SYSCLK clock speeds, along with other bus clock speeds such as HCLK (AHB bus clock), PCLK1 (APB1 bus clock), PCLK2 (APB2 bus clock) by increasing their prescalers should also reduce power consumption.

I do not know if you are using other peripherals such as SPI, DAC/ADC, I2C, but if you do have them, they contribute to the microcontroller's power consumption too.

Check this link here, the tricks listed above can be found on page 10 of that link. Although the link provides tricks for the STM32F3, some of the tricks listed there are still applicable for the STM32F4.