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TPS2540: TPS2540 overcurrent Fault exit

Part Number: TPS2540
Other Parts Discussed in Thread: TPS2546

Im using a TPS2540 in a basic usb charger circuit, set to Dedicated charging port, auto-detect mode(CTL1, CTL2=0, CTL3=1). Current limit is set to aprox. 1.2A. It works fine, but once I try to overload (add an extra load of 5R6 parallelly, while it charge a device) it assert the fault condition and reduce the charge current. Removing the extra load the fault LED turns off, but the charge current still remain at lower level aprox. 400mA. It rise back the charging current to normal level of +1A, just if I disconnect and reconnect the charged device. Is this normal ? It would be better if the IC do it by itself.

  • TPS2540 current limit works by reducing the OUT voltage in order to keep the current at Ios (1.2A for your case). The phone probably went into a "brown out" state and lost memory of what type of charging port it was connected to and as such had to default to a low charging current level. In order to charge again, the phone would have to be reconnected in order to read what type of charging port before charging at higher levels.

    Some of our newer parts (TPS2546 for example) have more advanced DCP auto schemes which monitor current and can auto switch with OUT discharge (automatically) in order to reset the phone. TPS2540 is a pretty old part.

  • Thank you so much Eric !

    All the best !