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SN74LVC1G17: SN74LVC1G17DCKR Input current specification

Kevin Raman
Prodigy 60 points
Part Number: SN74LVC1G17

Tool/software:

Hi,

I want to ask about the input current for SN74LVC1G17DCKR.

It is written in the datasheet that the input current, A, needs to be a maximum of 5µ A. However, I have trouble finding any reference design that actually mention that we need to control the input current and explaining why.

I am supplying 3.3 V through an optocoupler into the Schmitt Trigger and to get 5µ A, I will need a series resistance of 660k Ohms and this will be slow down our IO response time a lot. I would like to know if it is okay to use about 68k Ohms (~50m A) instead of 660k Ohms?

Appreciate any help I can get. Thank you.

  • 0
    Guru 295240 points

    The input leakage current is specified in the electrical characteristics table. This means that under the specified test conditions, the input current will never be exceed 5 µA, regardless of what your circuit is doing. You do not need to do anything.

  • 0
    TI__Mastermind 21410 points

    Hi Kevin,

    Like Clemens said, the leakage current spec is not something you need to supply but rather a characteristic of how much current "leaks" through the gate of the CMOS input fet to our device. This is to let you know how much current our device's input might source from your microcontroller or whatever you are using to drive it under normal operating conditions.

    Best,

    Malcolm

  • 0
    Prodigy 60 points

    Based on the datasheet, so the Il is actually "Leakage Current" ? 
    If so, does that mean the input of the Schmitt does not need a series resistor to control the current supplied to its input?

  • +1 in reply to Kevin Raman
    Guru 295240 points

    Yes; you can connect the input directly to GND or VCC.