What is the most reliable way for clocking multiple devices

[mazielvc]

Posted on May 05, 2017 at 20:15

I have a SMT32F7 for control one STM32F4 for comms (ETH MII) and the ETH PHY and I was thinking either one of these (Inclining for number 3):

But I'm not an expert and would like to know what is the most reliable of these:

Or should I use 3 different clocks?

Thank for your help.

[Tomas DRESLER]

Posted on May 05, 2017 at 20:24

What nature is the CLK 25MHz? Crystal or oscillator?

If oscillator, a solution no. 6 when all devices are supplied from the oscillator - most stable and least jitter.

If crystal, I'd prefer no. 2 - the F4 can stop or restart the PHY. Anyway, if precise clock fails, ETH won't work too reliably.

[Tesla DeLorean]

Posted on May 05, 2017 at 20:27

If CLK 25MHZ is a TCXO, option 6, buffer the same clock into all three.

Do you want to control the clocks going into the STM32F4 and ETHPHY? ie turn on/off, low power

[mazielvc]

Posted on May 05, 2017 at 20:32

That's great! Both agree on number 6 independently.

That's the way I'll go.

Thanks so much for your help.

[Tesla DeLorean]

Posted on May 05, 2017 at 20:28

snap

[mazielvc]

Posted on May 05, 2017 at 20:29

Hi Edison, Is an oscillator (MEMS probably, still working on the design)

Thanks for your reply. Do you think I need 2 or 3 buffers for splitting the clock for your solution?

[mazielvc]

Posted on May 05, 2017 at 20:30

Hi Clive, No I don't need to.

Thanks