high power consumption of mcu rather than mentioned values in datasheet

[Srinath_03]

hi,

I am using Nucleog474ret6 board , and I am  measuring current across JP6(header) which is vdd section of MCU.

And measuring current using digital multi meter. As  measured current value is around 1.98mA(milli Amps)  while reset the MCU.

But the current value mentioned  in datasheet is around micro amps. 

code also erased from flash , just normally checking the current consumption of the MCU.

what can be the problem , or is this correct.

thanks,

srinath

[Andrew Neil]

Have you isolated the on-board ST-Link?

[Srinath_03]

Hi Andrew Thanks for the reply,

i have just removed the JP5 jumper which is the power section of 5V_STLK(st-link). and directly giving 3.3V at jumper JP6 for MCU, still we are getting same 1.98mA(milli Amps) while RESET. Is this correct way of isolation of ST-LINK.

is there any other way is there to isolate the onboard ST-LINK of NUCLEOG474RET6.

[Andrew Neil]

You also need to break the SWD and NRST connections.

There may also be a target voltage sensing connection ...

[Srinath_03]

Hi sir , i have removed the solder bridges of SWD and NRST jumpers and I am reading 9mA current in the VDD section of MCU. And I am giving same 3.3V .

[Danish1]

If the code is erased from the FLASH, then the stm32 processor is probably running ST's own bootloader program.

I would expect the current consumption running the bootloader to be much higher than it would be in a low-power mode, as it is actively waiting for you to download some code into the FLASH. But I have never measured an stm32 in this state.

[Srinath_03]

Hi sir,

i have attached the images of measured current at low power modes and normal run mode.

before i have erased code from the flash , that time the measured current is around 1.9mA. after that st community member suggested to remove the SWD and NRST of st_link at that time the measured current is around 9mA, which is very much large than usual current.

now i have attached the current measured during low power mode is 9mA, and without low power mode is around 29mA.

can some one suggest whether the measured current is correct or not. but as per the datasheet the current value is given as micro amps.

[BarryWhit]

Hi Srinath,

Power consumption depends on clock frequency, whether in low-power mode or not. So no one can tell you what you should be measuring without that information. The CubeMX GUI under the tools tab has a "Power Consumption Calculator" (PCC) you can use to more easily find expected power consumption, based on active peripherals, clock rate, voltage.

In particular, note that the G474 has several "low-power" modes, and you have to be careful about naming them exactly. For example, Your code calls HAL_PWR_EnterSLEEPMode(PWR_MAINREGULATOR_ON,...).

This is indeed a "low-power" mode, but it is only "regular" "SLEEP" mode, and not what's called "LOWPOWER_SLEEP" or "LP Sleep" in the documentation.

Without any peripherals on, clock at 150Mhz, and 3.0V the PCC tool estimates that power consumption in normal SLEEP mode is 6.1mA, which seems closer to what you're measuring. 

Update: and the 3 LEDS In your photo may account for the extra 3mA.