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TPS2047B max output current

Allen Wachter
Expert 6530 points
Other Parts Discussed in Thread: TPS2047B, TPS2553

Customer is using the TPS2047B CURRENT-LIMITED, POWER-DISTRIBUTION SWITCH to limit the power drawn by any of 3 USB ports.

He is finding that he can draw well over 1.1A continuous thru any port and the OC pin doesn’t go low.

Was expecting the max current on any single port to be around 700mA per spec. 

Any thoughts on what is happening here? 

Thanks

  • 0
    TI__Prodigy 270 points

    Hi Allen,

    The TPS2047B uses a sense-sense scheme with a smaller sense-FET and current-sense element in parallel with the main MOSFET.  The result of this is that the current-limit is a function of the VDS across the device, and the system-level impact is that the current limit at a smaller VDS is higher than at a higher VDS, i.e. the short-circuit current-limit will be lower (0.3A/0.5A/0.7A per the datasheet) than what you can pull as you slowly overload the port up to 1.1A.  Try increasing the load and you will notice the current folds-back to the datasheet limit for short-circuit current.

    If a "flat" IDS vs. VDS curve is desired, I would recommend the TPS2553.  It uses a series sense element so the current limit is independent of VDS, which means the short-circuit circuit will be the same as the overload current.

    http://focus.ti.com/lit/ds/symlink/tps2553.pdf -- Figure 4 has a good curve for reference.

    Hope this helps,

    Steve Tom