We are using STM32L452 for our project.
We have problem with pin NRST.
We set a 30K pull-up resistor (with pull-down capacitor of 0.1uF).
Sometime voltage on the NRST pin is 3.3V and sometimes it is 1.4V.
In cases it is 1.4V the MCU is stuck.
We think that in case of 1.4V happens because a pin leakage current.
Do you have any solution for us ?
Probably when you see "1.4V" it's really a combination of 0V and 3.3V as the MCU continuously resets. Are you measuring on a multimeter or an oscilloscope?
The solution would be to find out why it's resetting and address the issue. Look at the RCC->CSR flags on startup to determine the cause of the reset. Perhaps a watchdog reset? Debug, step through, to determine where the problematic code is. Probably not a power supply issue, but it could be.
Please also note that in contrast to MCUs of the last millennium, a pull-up is no longer necessary (is also stated in the RM mentioned before). Examples like on the Blue Pills or Black Pills should be seen as a bad example here.
Could be a power issue. The portion of your schematic that you showed wouldn't be causing this issue. Measure VDD when NRST is at 1.4V.
Can you connect to the chip? Can you upload a program and step into it and debug?
Try looking at the NRST pin with an oscilloscope (or measure the AC Voltage part with a multimeter). If there are pulses, they are generated by the MCU internal reset. Maybe engaging the debugger somehow helped overcome the place in the code that caused the reset (adding a delay or something else...). I would also look at the config registry (CubeProg) to see if WDT and other sources of reset are disabled in it.