AnsweredAssumed Answered

STM32F746VGT6 with LAN8742A. RMII clock from MCO or shared oscillator

Question asked by Zoran Najdovski on Jan 30, 2017
Latest reply on Jan 31, 2017 by T J

Hi all,

I've read several forums regarding the potential ethernet instability by supplying the clock for an RMII Ethernet PHY chip from MCO of an STM32F4. This is one in particular stood out I have also seen this topic discussed in this ST community forum.
My next project is to develop a custom board for the STM32F746VGT6 with an ethernet PHY chip (LAN8742A). The STM32F746G-DISCO PHY chip (LAN8742A) shares the same clock as the F7 (NZ2520SB-25.00M) at 25 MHz. So i thought this might be the best approach for the F7. However, i have seen the F7 used with a similar PHY chip (LAN8720A) in RMII with the clock supplied by MCO.
What is the go-to design approach for ethernet data stability/reliability/low jitter? I am also looking to add USB to the board and will need to meet the clock requirements to run both USB and Ethernet simultaneously.
Thanks in advance.