I am using USB2517 - USB 2.0 Hi-Speed 7-Port Hub Controller IC to make a USB 2.0 hub.

What I do not understand (or its missing from the IC's datasheet), is Pins OCS[7:1]_N, which are "Input from external current monitor indicating an over-current condition".

overcurrent active low or high

I do not understand if that pin is Active Low or active high. Do I need to send a 0V signal to indicate there is no overcurrent, or a 3.3V signal to indicate there is no overcurrent?

As a note, the datasheet says this pin has a internal pull up resistor, but this does not help me understand what level signal I need to send to activate the overcurrent condition.

I guess since there is a internal pull-up, then 0V are used to indicate overcurrent?

This information from the datasheet is either missing or its plain obvious.

Otherwise, I will have to contact microchip to ask for support.

  • \$\begingroup\$ Even if _N suffixes are not given, the {Note} gives a clue: Since those terminals are inputs with internal pull-ups, they see logic-hi when left floating. So it's obvious that the inputs should be active-low. \$\endgroup\$ Sep 24, 2021 at 9:46
  • \$\begingroup\$ I know, I was thinking about that, but I then said "wait, what if the IC wants to keep the overcurrent protection passively active by pulling the pin high?" \$\endgroup\$ Sep 24, 2021 at 9:49

1 Answer 1


The _N typically indicates 'negated' and thereby it is active LOW.

  • \$\begingroup\$ Okay, it was plain obvious. Thanks! \$\endgroup\$ Sep 24, 2021 at 9:42

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