STM32WB15CCY6 excess current draw

[rhorner_tamu]

Hello,

I am having an issue with programming a custom made board utilizing the STM32WB15CCY6, utilizing the WLCSP49 package. The boards were designed by me, see relevant section attached, and I had the boards manufactured and assembled by a professional third party company. 

We used the Nucleo-WB15CC to develop a program before I ordered the custom PCB. We attempted to upload a sample program using STMCubeProgrammer with the STLINK-V3SET over the programming header, as well as supplying an external 3.3V.

We were able to connect to the MCU, however, when trying to upload the binary, we always received the error "Unable to Get CoreID" despite being able to connect to the device. Eventually, we were able to successfully upload a sample program using the Arduino IDE

Before uploading the code, there is minimal current draw from the external power supply. After uploading any program, the current maxes out at 0.5A, and drops the voltage down to 2.7V, current limited by the power supply, and the MCU begins to heat up. 

In trying to figure out the issue, I have eventually removed every other component on the PCB until only the MCU and the cap/ resistor for NRST remain. The problem persists.

I have tried across several PCBs, and the same problem is happening, no power draw until a program is loaded, then it shorts out.

[STTwo-32]

Hello @rhorner_tamu and welcome to the ST community.

I think it may be a HW issue on your design. So, first, I suggest you have a look at our HW design getting started guide AN5290. Also, the power supply schematic on the figure 13 of the DS13258 Rev 10 may help you. I've personally done a quick check, and I suspect an issue on the Power SMPS Pins (I'm not a HW expert to confirm).

Best Regards.

STTwo-32

[rhorner_tamu]

After doing a bit of reading on SMPS, I think it is correct for what I want to do. I am trying to minimize space and do not want the extra components. On the next version of the board, I was planning on running it at 1.8V. Is there something specifically I must do to turn it off?