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RE: power delivery question from Liaison report

Title: RE: power delivery question from Liaison report


1)  I was just using the same tolerance that Arlan Anderson used in the power number that he presented.

The 8% variation is at least a ballpark number and a starting point, but +/- 1% is probably way too tight for this application.

There is obviously some tolerance to which power supplies can be designed and manufactured.
Tight tolerances call for tight regulation, which is something that costs more.
Also, for the case of the negative resistance load, which we certainly will have, tight load regulation at the PSE is not good.

Our power experts should give us feedback on these numbers.

2)  I was suggesting that having a current and a power limit, in the PD, set at the long cable lengths
can also take care of current imbalance at the short cable lengths.

For long cables: the 350 ma current dominates, but current per pin is balanced
For short cables: the max power dominates, and the total load current is reduced due to more voltage at the load.

Otherwise, some one could design a PD that always grabs 350 ma, then at short cable lengths, we go over the current
per pin limit of 175 ma due to line resistance mismatch.

- Rick