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AM26LS31CDR

Harish Gudimetla
Prodigy 30 points


Hello Team,

Few days back I had a query regarding the FFF compatibility of AM26LS31CDR with DS26LS31CMX/NOPB and it was confirmed by your team that AM26LS31CDR can be used as a replacement for DS26LS31CMX/NOPB and also the PDN document says that they both are electrically compatible. But now if I see the datasheet, I find there are some differences in the switching characteristics of both IC's. Can you suggest me are these timing differences will affect any design as per the EMI point of view?

  • 0
    TI__Guru 53172 points

    Hi Harish,

    They basically are still going to act the same - and the changes are marginal at most.

    1. The devices are rated for 10Mbps max - so minimum bit time is 100ns; so that means propagation delay needs to be < 100ns - both devices meet this without issue. The AM device has about ~5 additional ns for the prop delay but worst case scenario you aren't looking anywhere above 20ns - so realistically this change shouldn't impact overall system. 

    2. The AM device does enable and disable slightly more slowly - but both devices worst case will still enable/disable in under 50ns - so the only potential impact is that if in the application the timing from enable to data transmission is very tight and requires the enable to data-transmission speed to be no more than what the DS device does there could be an issue - but this most likely is an edge case; both devices are quick w.r.t. enable and disabling and the vast majority of RS-422 applications do not have that strict timing requirements. 

    3. The last difference really is between skew - but only the typical value - the AM device typically has 1ns of skew added where the DS device typically adds 2ns - but they are both maxed at 6ns - so the worst case is the same. So the change really is marginal - and shouldn't impact the system too much - but technically the AM device will typically perform slightly better - but overall the both devices are low skew.

    These really are the changes - the reason we say they are direct replacements is because while there are slight changes in specification the changes will not impact a systems function in the vast majority of applications. You should be able to directly drop in and the application should work without issue. 

    Please let me know if you have any other questions!

    Best,

    Parker Dodson