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Associate III
April 23, 2026
Solved

Pull up resistor in STM32WBA5MMG RESET circuit

  • April 23, 2026
  • 1 reply
  • 81 views

Dear Team,

I have a board contain STM32WBA5MMG and  AD5941. We have provided a single RESET for both the chips.

The circuit is given below.

Hariom_0-1776960825992.png

May Iknow will this cause any issues.

 

Regards

Hiyo

Best answer by Peter BENSCH

No STM32 requires a pull-up resistor at the reset pin (in your case R36 = DNP), because there is already an internal pull-up present (see RM0493, 12.3.2).

The reset pin also acts as an output if an internal reset is triggered in the STM32, so any devices externally connected to NRST also receive this reset signal. According to the data sheet, the AD5941 needs at least 1µs to detect a reset; the internal pulse generator in the STM32 typically produces a pulse that is at least 20µs long (unfortunately, the specification for tO(NRST) is mentioned in RM0493 but still missing from the data sheet of the STM32WBA55UG, however, the pulse generator should be identical to that of other STM32 devices).

Summary: In my humble opinion, there should be no problem connecting /RESET and NRST.

Regards
/Peter

1 reply

Peter BENSCH
Peter BENSCHBest answer
Technical Moderator
April 24, 2026

No STM32 requires a pull-up resistor at the reset pin (in your case R36 = DNP), because there is already an internal pull-up present (see RM0493, 12.3.2).

The reset pin also acts as an output if an internal reset is triggered in the STM32, so any devices externally connected to NRST also receive this reset signal. According to the data sheet, the AD5941 needs at least 1µs to detect a reset; the internal pulse generator in the STM32 typically produces a pulse that is at least 20µs long (unfortunately, the specification for tO(NRST) is mentioned in RM0493 but still missing from the data sheet of the STM32WBA55UG, however, the pulse generator should be identical to that of other STM32 devices).

Summary: In my humble opinion, there should be no problem connecting /RESET and NRST.

Regards
/Peter

HariomAuthor
Associate III
April 24, 2026

Hi Peter,

Thank you very much.