When an output of the TPS2054B is disabled (ENx=L) what are the limitations on how that output pin may be driven by other devices? I want to provide power to a circuit in two ways: through the TPS2054B when a USB connection is present, otherwise, through a 7805 voltage regulator driving the same +5V rail when external DC power is available.
Is it safe to tie multiple outputs together, say two, in a situation where either one or both of them will be enabled?
The TPS2064 datasheet specifically lists reverse current blocking as a feature in the summary. This is not listed for the TPS2054B. Does it not have this feature?
Are there any brief descriptions of what is different between the TPS2054, TPS2054A, and TPS2054B parts?
The TPS2054 prevents reverse current flow when the output is disabled. It didn't make it on the front page of the datasheet but it is stated on page 27 of the datasheet. The difference between the blank, A and B in the part number are revision numbers. The part was revised due to improved manufacturing processes. The biggest difference between the three devices is the on resistance of the fet. The on resistance gets lower with each revision so the B version will have a lower voltage drop across it when on and dissipate less power in the package.
It is okay to tie the outputs together as long as only one output is enabled at a time.