STM32WL55: High consumption by RF section

Zedder · ‎2025-03-25

Hello.

I'm using the Nucleo-WL55JC board with LoRaWAN End-Device firmware (US915 region).

To measure the current consumption of the RF section, I removed the JP2 (I_RF) jumper (as per the manual) and connected an ammeter.

The issue is that the RF section consumes around 80mA during reception, and the power consumption during transmission is also significantly higher than the datasheet values.

I checked the FE_CTRL_1 to FE_CTRL_3 signals, and they look correct. The SMPS output is about 1.5V, which seems fine.

However, as I understand it, the RF section's current consumption should not exceed 5mA during reception.

What can be wrong?

Measurements are attached.

AScha.3 · ‎2025-03-25

Hi,

>and connected an ammeter.

How this is connected ? no ground loop ?

Did you check, your "ammeter" is showing real value, i.e. take an 1k resistor 3v3 to gnd, giving 3mA and check reading ?

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Zedder · ‎2025-03-25

How this is connected ? no ground loop ?
Did you check, your "ammeter" is showing real value, i.e. take an 1k resistor 3v3 to gnd, giving 3mA and check reading ?

I'm using NRF-PPK2 for mesurement. Checked it with different resistors with current from 15µA to 150mA, everything seems correct - current corresponds to the resistance.

I tried different measurement methods: ammeter, ammeter with a USB isolator, ammeter as a power source connected to pins 16(3.3V) and 19(GND) with JP7(5V line) removed. The results were similar in all cases.