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BlueNRG-M2 idle power consumption too high

Lukasz Nowak
Associate III

I am building a non-connectable beacon using a BlueNRG-M2SP board, and an STM32L412 MCU as a host, and the power consumption of the M2SP board between advertisment phases is around 24 uA, which is over 10 times higher than what the datasheet says (2.1uA).

I am using ADV_NONCONN_IND and ADV_INTERV_MIN = ADV_INTERV_MAX = 16000 (10 seconds).

Is the 24uA current in idle expected in this configuration?

Are there any additional commands which can be sent over SPI to reduce the power consumption?

I flashed DTM SPI firmware on the M2SP board, version 2.1c

When the M2SP is put in reset, the measured power consumption drops to 0, as expected (5nA, according to the datasheet).

After initializing the hci, the MCU is put into Stop2 mode, and the measured power consumption is around 0.85uA, as predicted by the STM32L412 datasheet.

Lukasz Nowak
Associate III

There appears to be a strong dependency of the idle current on the Vin voltage. Here are the measurements, I am getting:

  • 1.8V - 3.5uA
  • 2.2V - 7uA
  • 2.3V - 9uA
  • 2.4V - 17uA
  • 2.5V - 26uA
  • 2.6V - 39uA
  • 2.8V - 52uA

The M2SP module is LDO-based. I wonder if the LDO has a ground current proportional to the dropout voltage.

Something like that should be documented in the datasheet.

The datasheet, however, specifies the 2.1uA current consumption in sleep, with LDO and at 3.0V. That level is roughly matched by measurements at 1.7 - 1.8V but definitely not at 3.0V

Could somebody from ST confirm or deny that my measurements are correct, please?