Standby mode on stmL433 drawing too much current

[SSmit.13]

Hi

   I have a a stm32L433 48 pin processor and trying to get it into low power. I am using the STLink-V3PWR module with stm32Cube Monitor Power module.   First of all I placed a known value resistor across the STLink-V3PWR to make sure it is reading the correct value, then tried the following:

1. I am using a MIC5219-3.3YM5-TR from the input with the STLink-V3PWR set to 3.6v.  And on its own it draws 85uA.

2. I then added all the resistors and capacitors needed and it measured 96uA.

3. I added the STM32L433 and programmed it to first run for approx 5 seconds in normal mode (16MHz), then drop into standby mode. On the output you can see it drop quite a bit, but the lowest current is approx 650uA (far too much current) as you can see on the graph below.

My code is below after 5 seconds of normal operation. I tried HAL_PWREx_EnterSHUTDOWNMode(); without Putting the Ram in Retention, but still the same,

void EnterLowPower()
{
	RCC->APB1RSTR1 |= RCC_APB1RSTR1_USBFSRST;
	RCC->APB1RSTR1 &= ~RCC_APB1RSTR1_USBFSRST;
	RCC->APB1ENR1 &= ~RCC_APB1ENR1_USBFSEN;

   __HAL_RCC_GPIOA_CLK_DISABLE();
    __HAL_RCC_GPIOB_CLK_DISABLE();
    __HAL_RCC_GPIOC_CLK_DISABLE();
    __HAL_RCC_GPIOD_CLK_DISABLE();


   HAL_PWREx_EnableSRAM2ContentRetention();
   HAL_PWR_EnterSTANDBYMode();
}

Any suggestions what I am doing wrong?

Many thanks in advance

Scott

[Andrew Neil]

Please show your schematic.

Remember that you must physically disconnect any debug probe to get true low-power readings.

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

[SSmit.13]

Hi

   Its a very min circuit to test it out. I replaced the TPS7A with the MIC5219-3.3YM5-TR.  I am using the STLink-V3PWR with the stm32Cube Monitor Power application. I dont use this for debugging and programming, I removed that, and repowered the board , so the above test was with only the STLink-V3PWR along with monitor app , no debugging was involved. Before doing this I placed a resistor across the STLink-V3PWR and the current is what was expected.

Best Regards

Scott

[SSmit.13 · Accepted solution]

I found out what the issue was. The STLink-V3PWR  was set for 3.3v , and MIC5219-3.3YM5-TR output is 3.3v. So when the voltage dropped the current went up. I set the STLink-V3PWR  to 3.5v and got down to 60uA in STandby and Ram2 retention.

Scott