DS26C31MQML: What is the difference between a DS26C31 and an AM26C31?

Hi Jeff,

There are a few differences - they are similar in architecture - a general overview is shown below:

So the big ones are:

1. Speed

2. Fault Protection

3. Common Mode Ratings

4. Temperature Range.

Can you explain the fault that you are seeing between the two devices?  I understand if you can't, but if you can show a snippet of the bus circuit that would be very helpful as well in determining potential issues. I am also open to discussing the issue through email ( I can message you my email address if you wish to go that direction) if you don't feel comfortable sharing information on our public forum.

Please let me know!

Best,

Parker Dodson

Hello Parker, 

Thank you for responding.  I am asking the team under what conditions they observed the failure. 

Meanwhile, I do not understand the large difference in the signaling rates.  How do you get max signaling rate from the datasheets? 

From the AC parameters, the DS26C31 is rather loosely defined at 14ns maximum rise and fall times.  I do not see any parameter describing data rate, but loosely 14ns x 2 comes out to 35MHz.   The AM26C31 is a faster part, with rise and fall times showing a maximum of 10ns x 2 is obviously much faster.  Yet the general comparison is showing the DS part is 3x faster than the AM part. 

What am I missing?

Hi Jeff,

Thanks for getting more information I appreciate it!

So it seems there is an issue with the comparison table data. A lot of datasheets don't include the data rate explicitly (some of them do but its hit or miss if its actually included). In general it is suggested the max data-rate a transceiver (RS-422/485)  can have is limited by its differential rise/fall time - this value should be no more than 1/3 of the bit time - so for a 30Mbps the max should be apprx. 11.11ns which depending on the variation of AM26C31 (2 variants are max of 10ns and 2 variants are a max of 12ns) so the data rate should be showing around 30Mbps for the AM26C31 - I apologize for the oversight generally the information in our tables is accurate but every once in a while a hiccup shows up . So both parts should be able to run at similar speeds (based on DS device potentially a bit faster but typically probably very similar). In most cases you can probably squeeze more data through the device - but if the environment is closer to boundaries of acceptable use the more strong that higher level data cap is going to become. 

Please let me know if you hear anything back from your customer and I will see what I can do from there to offer support. 

Best,

Parker Dodson

Hello Parker,

Thank you, that makes perfect sense.  I have not heard back from anyone on the team working this issue, likely due to the holiday.  I will follow up soon as I can.  Meanwhile, I wish you and your team a wonderful Thanksgiving.

Jeff