Can we power STM32WB0 from two external voltage sources?

[maxter]

We would like to power the VDD33 domain of an STM32WB0 device (STM32WB05KZ) from an external 3.3V source and the other domains from an external 1.8V source. In theory, it should be possible - by supplying 1.8V to VDDSD in SMPS BYPASS mode, or directly to VFBSD in SMPS OFF mode. However, it is not clear if the SMPS' input (VDDSD) is isolated from VDDIO (the power diagram in the datasheet shows there is a connection). Please clarify if it is possible to use the described configuration.

[STTwo-32 · Accepted solution]

Hello @maxter 

VDDSD has a dedicated ESD protection (no diode connected between VDDSD and VDD).

Yes, it is possible to supply VDDSD with 1.8V and VDD with 3.3V. When the SMPS is OFF (no inductor between VLXSD and VFBSD) VFBSD pin needs to be supplied with 1.8V and the rest of VDD at 3.3V (it's better to connect VDDSD to 3.3V as well).

I suggest supplying the whole device with 1.8V without SMPS, since there are not significant benefits in using different supplies for our device.

Best Regards.

STTwo-32