SN74AXC4T245-Q1: suitable for RGMII case

Hi Lijia,

It is perfectly acceptable to use SN74AXC4T245-Q1 in RGMII case. Across the board for all TXP devices channel-to-channel skew is typically <1 ns.

Please refer to this FAQ for channel-to-channel skew. Please refer to this app note per section 2.5 for further details regarding Voltage Translation for RGMII.

Best Regards,

Swathi Deivamani

Hi Swathi,

how about the skew between different devices? thanks!

Lijia

Hi Lijia,

I have 2 clarification questions:

1. Are you referring to the delay from Input to Output? If so, Tpd (propagation delay) is spec'ed in the datasheet.

Or

2. Are you asking about skew between SN74AXC8T245-Q1 Vs. SN74AXC4T245-Q1? If so, skew is measured from one channel to another within the same device and it isn't measured between different devices. Across the board for all TXP devices channel-to-channel skew is typically <1 ns.

Hope this helps. Thanks!

Best,

Swathi

Hi Lijia,

Just to double confirm, could you clarify your specific use case with a block diagram or schematic? 

I'm asking because RGMII application is typically for a 6/8ch use case. Hence, the 8ch is a better recommendation as it seems you intend to use multiple 4ch devices for the 6/8ch application, per your skew between different devices question. If so, we cannot guarantee such; as skew is within a single device similar to the referenced FAQ.

Hence, even though the 4ch device can meet the <2.6ns skew requirement for a single device (not different devices), the 8ch AXC works best for the 6/8ch application. Hope this helps. Thanks!

Best,
Swathi

Hi Swathi,

Thanks for the reply. Yes, RGMII requires more than 4 channel. I will suggest customer use 8T245. 

B&R

Lijia

Hi Lijia,

You are welcome. If there aren't any further concerns, please help mark this thread as "Resolved" in order to close the thread.

Please let me know if you have any questions.

Best,

Swathi