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Part Number: TPS23880
I'm testing this new EVM with several different PDs on it's 2-pair and 4-pair outputs.
Single signature on 4-pair works and turns on signal and spare pairs. However dual-signature on 4-pair only spare pair turns on, and signal pair does not turn on. Seems like it's not checking signatures properly. I also verified this with a split cable too, and only spare pair comes up. Is anyone else having the same issue?
Any help is appreciated. Thanks,
Can you please provide more information about your test condition.
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In reply to Penny Xu:
PoE Applications & Marketing Manager
In reply to Thomas Lewis:
I figured out the problem, and it had to do with the polarity of signal pair on this TI EVM being backwards from the standard ethernet cable wiring (which is allowed, of course, just unexpected), so I added a bridge rectifier to the PD I'm working with, and it seems to come up fine now on signal pair, spare pair. and both together in 60W tests.
Thanks for your help and checking in,
In reply to Paul Kottas:
Our EVM port polarity followed IEEE802.3bt standard. For Type 4 ports(right two 90W ports), you have to follow this rule: pair 3&6 is positive, pair 1&2 is negative; pair 4&5 is positive and pair 7&8 is negative. Please read this white paper to understand more details about IEEE802.3bt standard before the standard is published.
Hi Paul, The IEEE802.3at standard only allows 2 pair power delivery and it allows both polarity for 2 pair Alt A . But 4 pair power delivering is only allowed in IEEE802.3bt standard. If the PSE is Type 4, you have to follow the polarity defined for Type 4 which I described above. If you only use 2 pair (<=30W), it is considered as Type 3, Type 2 or Type 1, you can use both polarity as the picture shows. Thanks. Best regards, Penny
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