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SN74AXC8T245-Q1: channel-to-channel skew

Part Number: SN74AXC8T245-Q1
Other Parts Discussed in Thread: SN74AXC8T245

Hi, Clemens

I have two questions about SN74AXC8T245-Q1.

1. In datasheet, I didn't find the channel-to-channel skew specification, so what's the skew value?

2. In document SCEA065A ,SN74AXC8T245 is recommended in RGMII voltage translation application, so whether this case has been validated in communication products or other products, whether it is a fully validated application?
Thank you.



  • Hi Gavin,

    We don't spec channel to channel skew. However, we can guarantee it to be less than 1ns for this device.

    We recommend the part for RGMII voltage translation applications because it meets the generic protocol definition of RGMII (voltages, frequencies, setup/hold times).

    You should always make sure by looking through the datasheet whether the part supports your requirements.



  • Hi, Karan

    Thanks for your help, another question need you confirmation.

    As what you said, the maxim channel-to-channel skew will less than 1ns, so what‘s the accurate defination of this 1ns, which of the following figures (figure A or figure B) accord with your test result?


    Thank you.

    Best Regards.


  • The skew between any two channels is less than 1 ns, as shown in figure B for Bx and Bz.

    However, the edge of channel By can be anywhere between the left and the right line, so the Bx-By skew or the By-Bz skew can still be as large as 1 ns. (If one is larger than 500 ps, the other one must be smaller than 500 ps.)

  • Hi Gavin,

    What is your application with the skew requirements? and what is the desired skew for your application?

    We only consider channel to channel skew within a single device and cannot guarantee between device to device. We have typically measured channel to channel skew of between150-200ps on the SN74AXC8T245 for 1.8 <>3.3V translation. This should be good for most of the high speed applications, for eg RGMII which requires 500ps max skew.

    Channel to channel skew can be defined as the max difference in the prop delay between any 2 channels of the device driving into equal loads and receiving input with no skew( inputs arriving at the same time on the channels). According to your figure, the max skew is 2ns in FigA and 1ns in FigB.

  • Hi Gavin,

    Please refer to the application note:

    This talks of typical applications of AXC devices for standard interfaces and has an example of skew measurement at the end.

  • Hi ,Shreyas

    Thank you very much for your answer. My application is RGMII volatge translation. According to your answer, I think the channel to channel skew of SN74AXC8T245 can meet the RGMII TX skew requirement(±500ps).