We have designed, build and assemble a board with a STM32U575OGY6QTR. The first tests went well with the ST-LINK/V2 programmer connected to the board (driving the NRST). Now we have removed the programmer, and under some circumstances the MCU does not start. Adding an external pullup on NRST starts the MCU. DS13737 (page 227/321, Rev 4) recommands an external 0,1 µF capacitor that we unfortunately do not have.
"Under some circumstances" means that it depends on the power supplies. Externally our board is powered under 25 V, then we have a SMPS producing 3.0 V, then a LDO producing 2,5 V that powers the MCU. The MCU starts only when the external power is less than 24 V, however all voltages are always good.
Previously we have designed, build and assemble a (mock-up) board with a STM32U575VIT6Q, everything went well (even without 0,1 µF capacitor).
Is the value of R_PU package dependant? (internal pullup)
Thank you
