[FAQ] AM6442: Clock Specifications for SERDES0_REFCLK0N SERDES0_REFCLK0P and USB3

Hello TK,

Thank you for the query.

Please refer SK-AM64B for USB3 implementation

For the clock accuracy requirement when USB and ethernet is used, refer below section of the SOC data sheet

Table 7-19. MCU_OSC0 Crystal Circuit Requirements

 Regards,

Sreenivasa

Hello TK,

Refer below input based on my discussion with the device expert

SERDES0 configured for PCIe interface 

25MHz clock - ±100 ppm when ethernet interface is not used 

25MHz clock - ±50 ppm when ethernet interface is not used 

Follow the PCIe specification for all requirements including the clock accuracy related to this peripheral.

SERDES0 configured for USB3.1 SuperSpeed

25MHz clock - ±100 ppm when ethernet interface is not used 

25MHz clock - ±50 ppm when ethernet interface is not used 

Regards,

Sreenivasa

Hello Sreenivasa,

Thank you for the detailed explanation.

After reviewing the SK-AM64B schematics, it appears that there is no clock connected to the SERDES0_REFCLK0.
Could it be that my initial question was based on a misunderstanding and that the REFCLK is not required?

If I understand correctly, connecting an appropriate crystal oscillator to MCU_OSC0 (in this case, 25MHz ±50ppm for Ethernet) should suffice.
This is very helpful information as it means I can avoid implementing an unnecessary REFCLK circuit.

Thank you very much for your assistance.

Best regards,
TK

Hello TK, 

Here are a few E2E references that could help.

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/854754/tda4vm-serdes_refclk

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/854183/tda4vm-treatment-for-serdes_refclk

Regards,

Sreenivasa