TMS320F28388D: TMS320F28388D clock

Sammi Shang

Part Number: TMS320F28388D

Dear team,

Customer see a multi-channel clock buffer used for provide clock for DSP and 2 PHY interface in a application note. They want to know any special requirement for the clock of DSP and PHY? Can customer use separate clock for DSP and 2 PHY? Or how about using the clock of DSP for PHY?

Thanks.

Best regards,

Sammi

over 5 years ago

0 Sudharsanan over 5 years ago

TI__Expert 5391 points

Hi Sammi,

Can you please elaborate a bit more..which Application note is being referred to?

Which module/model of PHY and over which interface of F28388D?

Regards,

Sudharsanan

0 Sammi Shang over 5 years ago in reply to Sudharsanan

TI__Expert 4450 points

Hi Sudharsanan,

Thanks for your reply. Customer want to know if it is right to connect clock of 28388 directly to 2 PHY ICs, as below picture shows?

Thanks.

Best regards,

Sammi

0 Vivek Singh over 5 years ago in reply to Sammi Shang

TI__Guru** 115881 points

Saami,

Our recommendation is to connect same clock source to device and both the PHYs which means connect 25MHz clock to device input and both the PHYs.

Regards,

Vivek Singh

0 Cody Watkins over 5 years ago in reply to Sammi Shang

TI__Mastermind 42195 points

Sammi,

as Vivek stated our recommendation is to use a single 25MHz clock to the c2000 and both EtherCAT PHYs. This is a requirement from Beckhoff.

The clock buffer is only required depending on the drive strength of the oscillator or crystal used. If your oscillator has enough drive strength for all 3 devices there is no need for a clock buffer.

Regards,
Cody

0 Sammi Shang over 5 years ago in reply to Cody Watkins

TI__Expert 4450 points

Hi Cody,

Thanks for your reply. If external clock to both C2000 and PHY, what's the purpose of GPIO154?

Thanks.

Best regards,

Sammi

0 Sammi Shang over 5 years ago in reply to Sammi Shang

TI__Expert 4450 points

Hi Cody,

Another question, customer was not clear how to know if the oscillator has enough driver strength for 3 devices. Any specific description of this?

Thanks.

Best regards,

Sammi

0 Vivek Singh over 5 years ago in reply to Sammi Shang

TI__Guru** 115881 points

HI Sammi,

GPIO154 is provided to use for external PHY but there is some PPM requirement for PHY CLK which may not be fulfilled when using it. In that case user will have to adjust some FIFO level and test the end application to make sure it works. We are working on developing a app report for this which should be available by end of the year.

Regards,

Vivek Singh

0 Cody Watkins over 5 years ago in reply to Sammi Shang

TI__Mastermind 42195 points

Clock have a specific drive strength. If you exceed that i'm not entirely sure what would happen, it may fail to start or lose signal integrity. You should be able to look up more information with your crystal or oscillator manufacturer.

Regards,
Cody

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TMS320F28388D: TMS320F28388D clock