BlueNRG-LP Current Consumption

[TLans.1]

Hi, I am evaluating the current consumption of BlueNRG-LP using STEVAL-IDB10V1 and i am a bit confused with the expected and actual device's currents.

According to the datasheet, peak TX current during connection at 0dB is 4.3mA, according to Current Consumption Estimation tool it is 5.43mA and in my measurements i get 5.6mA.

For peak RX current, datasheet specifies 3.4mA, in Current Consumption Estimation tool its 3.73mA and in my measurements i get 5.6mA (same as TX).

Any idea why the difference especially between the datasheet and the estimation tool? Which value should i expect?

[Laurent LOUAZON]

Hello,

Please keep in mind Rx and Tx consumption given in datasheet are RF block only so that CPU power consumption must be added (this is the way all BLE manufacturers are handling this point).

Power consumption tool is the right tool for having a global power consumption view. From our test this is quite accurate versus practical measurement.

So, on top of 4.3mA for Tx 0dBm given in datasheet you must add CPU power consumption. Considering CPU running in direct_hse (around 1.1mA) as per power consumption example, you will get a total around 5.4mA in Tx 0dm.

In Rx, for having global power consumption you should as well add Rx datasheet power consumption with CPU power consumption. Please also keep in mind, datasheet Rx power consumption is given at sensitivity level (so full AGC gain). So Rx current will depend on RF condition at some point.

Then regarding your practical testing, I guess you are measuring at JP1.

Please be careful about various possible leakage that could impact hundreds of uA here.

Few HW test recommendations:

• Please measure exactly Vbrd on your evaluation kit and apply exactly the same voltage level as external Vblue (if you set externally a 3.3V while Vbrd is 3.29V for example, this will create leakage with external components supplied at 3.29V)
• Avoid UART leakage with STM32F1 on eval kit. To do so, you can put STM32F1 (USB/UART & CMSIS DAP) in DFU mode to avoid leakage
  • plug USB cable on CN6 prior setting Vblue1 voltage externally or press reset button before plugging USB cable on CN6
  • STEVAL kit appears as “maintenance�? when in DFU mode 2
  • Power on board on Vblue1

Also possible to have some SW parameters impacting current consumption such as LSE low drive configuration (system_BlueNRG_LP.c file). This is the gain of LSE that can have up to few hundred uA impact. It can be set depending 32kHz xtal selected from low to high drive.

Setting LL_RCC_LSE_SetDriveCapability(LL_RCC_LSEDRIVE_LOW) will ensure min drive and best power consumption for example.

Regards

Laurent

For example

[TLans.1]

Thanks Laurent. This really helped.