STM32L562QEI6 doesn't boot on board power up

[RandomGaurav]

Hello all,

I have got a custom designed board using STM32L562QEI6, in which the MCU doesn't boot up upon powering up the board. However, upon pulling the NRST pin low manually and then releasing it, the MCU does power up. I have checked the voltages before and after asserting NRST and everything is stable and as per expectation. This observation was noted every time and followed the same behaviour.

On other boards using the same design, this issue doesn't exist.

Hoping to find some help in this regard.

[Andrew Neil]

Welcome to the forum.

As it's a custom board, you will need to show your schematic - see: 

How to write your question to maximize your chances to find a solution 

Did you follow AN5211, Getting started with STM32L5 Series hardware development, and the datasheet recommendations in your design?

Have you compared your design to ST boards ?

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@RandomGaurav wrote:

On other boards using the same design, this issue doesn't exist.

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How many other boards? Are they from the same or different manufacturing batch?

It could be that the design is marginal.

It could be that this board has a manufacturing fault or error(s)

Have you used an oscilloscope to see what's going on?

[AScha.3]

Hi,

so its just this board with a problem, other boards running fine ?

Maybe cap on nrst too small or not soldered, so cpu starting too early, while vdd too low.

Check cap, or solder/add bigger cap to test.