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SN74AHC14 input current

Lopa Patel
Prodigy 50 points
Other Parts Discussed in Thread: SN74AHC14

We are doing some failure analysis and testing of diodes external to this part and want to make sure we do not damage this part. 

If we have a 26 mA current source at the '1A' input pin of the SN74AHC14  will it stress the device?  What about -26mA current source? What should the current at the input pins be limited to?

If we have a 26mA current source at the '1Y' output pin of the SN74AHC14  will it stress the device?  What about -26mA current source? What should the current at the output pins be limited to?

  • 0
    TI__Mastermind 46480 points

    Hi Lopa

    The absolute max limits are specified in the datasheet

    . -20ma for inputs and +/-20ma for outputs.

    Anything beyond these limits will void the warrantee and could damage the part.

  • 0 in reply to Chris Cockrill
    Prodigy 50 points

    Hi Chris/TI engineers,

    So does that mean that I can put NO positive current source at inputs or does it mean that the part can handle a significant amount of positive input current?

    I don't know why only a negative 20mA is spec'd for inputs.  What is the positive limit?

    Thanks!

     

    - Lopa

  • 0 in reply to Lopa Patel
    TI__Mastermind 46480 points

    The Diodes on the inputs that are connected to Vcc are back to back so they cannot be tested. This is done to allow voltages on the input above Vcc. You should not go above the max input voltage on thes pins.

  • 0 in reply to Chris Cockrill
    Prodigy 50 points

    Hi Chris or TI engineers,

    Please help answer my question regarding positive current, not voltage at the inputs of this part.  The replies above do not help me understand what is the max input positive going current that this device can be subjected to.

    My question is whether the inputs can handle any amount of positive current source 3mA? 1mA?  30 mA? 0 uA?

    I will not exceed the voltage. 

    I do not care to test the diodes internal to your parts.  We are trying to test diodes outside your part and do not want to damage your parts in the process.  

    If it is easier to talk about this over the phone, then please give me a number I can contact you at.  Thanks for your help.

  • 0 in reply to Lopa Patel
    Prodigy 50 points

    Hi Chris,

    Any updates on this, if I don't exceed the voltage, could I have some uA of current source out there?  We have a zener diode at the input that we are trying to test.  We don't think the SN74 part will see much current.

    Thanks for your help. 

    - Lopa

  • 0 in reply to Lopa Patel
    TI__Mastermind 46480 points

    I don't think there will be no problems.  If they dont exceed the voltrage then there should be almost not current into the part.