HiMXRT1060-EVK Ethernet speed

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HiMXRT1060-EVK Ethernet speed

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patriciocohen
Contributor IV

Hi guys,

I'm looking at the schematic of the MIMXRT1060-EVK and I see that the KSZ8081RNB is configured in 10Mbps mode (1k pull-down). Is that ok? Have anyone of you tested the board in 100Mbps mode? I don't have the EVK available, so I can't test it.

I'm asking these because in the schematic there are 49.9R external termination resistors for the TX and RX diff pairs, but the PHY datasheet says these resistors are not necessary, since they are integrated inside the PHY. With this in mind, these external resistors are modifying the characteristic impedance of the diff pairs and can be detrimental for 100Mbps mode.

Can anyone confirm that 100Mbps speed is possible with these EVK? We are designing a custom PCB based on this EVK.

Thank you!

Patricio

 

 

 

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mjbcswitzerland
Specialist V

Hi

The strap resistor causes the PHY to start in 10Mbps mode of operation but typically the Ethernet/PHY driver will then set it to the mode that is required during operation - often auto-negotiation so that it will (almost always) today work at 100Mbps.

I use all EVKs (1020, 1050, 1060, 1064) at 100Mbps without any issues.

I am not aware of the integrated resistors in the PHY and didn't find any reference to them in the data sheet that I have. However, if the recommendation is not not use external ones, it would be better to not have them. In any case this concerns component mounting so I would copy the circuit and just don't stuff the Rs if you can confirm that this is the optimal solution for your final HW.

Regards

Mark
[uTasker project developer for Kinetis and i.MX RT]
Contact me by personal message or on the uTasker web site to discuss professional training, solutions to problems or product development requirements

For professionals searching for faster, problem free Kinetis and i.MX RT 10xx developments the uTasker project holds the key: https://www.utasker.com/iMX/RT1060.html

 

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4 Replies
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carstengroen
Senior Contributor II

Patricio,

you are correct, the termination resistors should not be there. They are however, mounted on all the NXP EVK's, for what reason I dont know.

carstengroen_0-1606467300227.png

 

I have (own) boards running with this design, works perfectly (with auto negotiation on 10/100)

carstengroen_1-1606467365469.png

 

1,575 Views
patriciocohen
Contributor IV

Hi carstengroen,

Thank you very much for the info. With Mark's reply and yours now I'm 100% confident about the design.

Best regards,

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1,594 Views
mjbcswitzerland
Specialist V

Hi

The strap resistor causes the PHY to start in 10Mbps mode of operation but typically the Ethernet/PHY driver will then set it to the mode that is required during operation - often auto-negotiation so that it will (almost always) today work at 100Mbps.

I use all EVKs (1020, 1050, 1060, 1064) at 100Mbps without any issues.

I am not aware of the integrated resistors in the PHY and didn't find any reference to them in the data sheet that I have. However, if the recommendation is not not use external ones, it would be better to not have them. In any case this concerns component mounting so I would copy the circuit and just don't stuff the Rs if you can confirm that this is the optimal solution for your final HW.

Regards

Mark
[uTasker project developer for Kinetis and i.MX RT]
Contact me by personal message or on the uTasker web site to discuss professional training, solutions to problems or product development requirements

For professionals searching for faster, problem free Kinetis and i.MX RT 10xx developments the uTasker project holds the key: https://www.utasker.com/iMX/RT1060.html

 

1,586 Views
patriciocohen
Contributor IV

Thank you Mark!

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