Wich is the STM32F429 PLLN maximum frequency?

[TCabr.1]

User' manual says that the maximum PLLN or VCO output frequency should be between 100 and 432 MHz (pg. 227). However, I was trying to set the PLL clock and the SysClock to 180 MHz and also respect the 48 MHz clocks.

One possible solution is to set the PLLM to 4, PLLN to 360, PLLP to 4, and PLLQ to 15. Although, it leads to a VCO output frequency of 720 MHz.

The curiosity was that it worked. USB frequency is at 48 MHz, PLL and SysClock are at 180 MHz. So, my questions are:

1 - What are the problems with the VCO output frequency at 720MHz?

2 - I'm using USB HS, not the FS one. So, should I keep the USB FS clock at 48MHz?

3 - How should I configure PLL to operate at 180 MHz and use the USB HS?

Ps. My PLL clock source is HSE at 8MHz.

[Alexander Czajor]

Hello @TCabr.1​ 

The obvious standpoint is the one of @TDK and @Community member​. Using the chip outside the specification is risky and will sometimes work, sometimes not. There might even arise quality issues, as using the VCO outside the spec can cause additional stress to the device with respect to ST's testing conditions.

If you need further assistance with this point I would recommend to use the online support channel in the support channel.

Many thanks

Alexander