AnsweredAssumed Answered

PLLRDY Not Going Active For External Crystal

Question asked by ryan.robert on Mar 1, 2013
Latest reply on Apr 7, 2014 by Clive One
I have three prototypes assembled that use the STM32F407 processor. Two of the boards work fine but the third board is having a problem with the clock setup.

I am using an external 25MHz crystal and setting the main PLL to output 144MHz. As I said, two of the boards work fine. On the third board HSERDY goes true but after configuring the PLL and turning it on, the PLLRDY flag never goes true. It will go true if I use HSI instead of HSE.

I am using a lightly modified version of the ST Micro code from the demo board (with 144MHz instead of 168MHz though I tried changing that as well). Works with the two other boards so I don't think it is a code issue.

It is the exact same circuit design as the demo board. I tried replacing the crystal and its caps resistor.

Any suggestions?

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