DP83869HM: RGMII Series Termination Details and Voltage Domain

Thomas Koerkenmeier

Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

On page 14 of the datasheet the following information can be found regarding series termination of the RGMII port:

This would imply that the series termination resistors are only on the RX pins of the port. Are they also included in the TX pins or will I need to add them external to the chip?

Also, what is the voltage domain of the RGMII signals? More specifically if I change the supply voltage on VDDIO from 2.5V to 3.3V will it impact the signaling levels of the RGMII interface? I plan to interface the RGMII of the DP83869HM to the RGMI port on another device where the voltage domain is 2.5V. Thanks

over 4 years ago

0 Hung Nguyen92 over 4 years ago

TI__Expert 5670 points

Hi Thomas,

The series termination resistors are normally at the transmit side of the transmission line. Thus, only RX pins have them (signal is travelling from RX pins of the DP83869 to the MAC).

The TX pins are at the end of the transmission line, so there is no series termination. On the TX side (signal is from the MAC to the PHY), the termination should be placed closed to the MAC, or can be internal of the MAC.

DP83869 device supports 3 different VDDIO levels (1.8V, 2.5V and 3.3V). Please refer to the datasheet for more information.

Regards,

Hung Nguyen

0 Thomas Koerkenmeier over 4 years ago in reply to Hung Nguyen92

Prodigy 30 points

I am aware that the device supports three different VDDIO levels. Does the VDDIO level have any impact on the voltage level of the RGMII interface or is the RGMII interface determined by one of the other voltage domains on the chip such as the VDDA2P5?

0 Hung Nguyen92 over 4 years ago in reply to Thomas Koerkenmeier

TI__Expert 5670 points

RGMII interface is operating off VDDIO supply. VDDIO level determines the voltage level of RGMII signals.

Regards,

Hung Nguyen

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DP83869HM: RGMII Series Termination Details and Voltage Domain