STM32WL5MOC Custom Board Power Consumption Too High

[JHCarter]

I have tested the LoRaWAN_End_Node example on a B-WL5M-SUBG1 board and I measure power consumption of 1.7uA when the processor is in STOP mode between transmissions.  This is exactly what I expected to see.

I designed a very simple custom board based on the B-WL5M-SUBG1 design, downloaded the same .elf file to it, and it communicates with my LoRaWAN gateway as I expect.  However I measure ~300uA current draw while it is in STOP mode.  I have compared my custom board schematic to that of the B-WL5M-SUBG1 several times looking for a difference that would account for that much extra power consumption and I just have not found it.

I am using STM32CubeMX v6.16.0, STM32Cube FW_WL V1.4.0, and the part is STM32WL5MOCH6TR.  I have attached the schematic of my custom board.

I am hopeful that someone can see what I have missed.

[JHCarter]

After reviewing DS13293 and AN4899 with regards to unconnected pins I tried defining all unused pins to analog input with a pulldown in STM32CubeMX.  It made no difference in my current draw.

I am still searching for answers on this.  Any suggestions will be appreciated.

[clintonkoepp]

300 µA in STOP screams “something is still drawing 1 mW somewhere.”
90 % of the time it’s a pin that isn’t hard-defined.

1. CubeMX → GPIO → every un-used pin → Analog, no pull.
2. PB0 (TCXO_EN) → GPIO_output_low before HAL_PWREx_EnterSTOPMode().
3. RF-CTRL1/2 → low; SUBGHZ → RadioSleep() then LL_RCC_RF_DISABLE().
4. SWD pins (PA13/14) → analog; remove debugger completely for the test.
5. If you fitted an external TCXO, make sure its VDD is off in STOP (PB0 low kills it).
6. Any I²C/SPI pull-ups? Measure voltage across them – 3 V ÷ 10 kΩ = 300 µA per resistor.
7. Still high? Probe VDDSMPS: if you see ripple the SMPS is awake; call HAL_PWREx_SMPS_DisableBypass() or force bypass and shut it down.

Do those seven and you’ll be back to the DK’s 1-2 µA.