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Schmitt Trigger SN74AC14N basic question about output

CurtissHawk
Prodigy 20 points
Other Parts Discussed in Thread: CD74AC14, SN74ACT14, SN74AC14

Hello,

I have one of these and I am only using one of the six circuits.  The other 5 circuit input pins are shorted to ground.

http://www.digikey.com/product-detail/en/SN74AC14N/296-4301-5-ND/375819

The input is from a voltage divider with a resistor and a light dependent resistor.  I measured the output by putting the positive probe of the voltmeter to the output and the negative probe to the negative rail.  I get about 125ma.  The datasheet shows 24ma per pin.  

Since I'm only using one of the 6 circuits does it mean that the output can be 6 x 24ma on one pin?  Or am I overdrawing current from it and will damage it long term?

Thanks,

Matt

  • 0
    TI__Genius 9860 points

    Hi Matt, the datasheet recommends the current through the output to be no greater than 24 mA. The device will still be functional at higher currents but the datasheet electrical characteristics will no longer be guaranteed.

    You can draw up to 50 mA on each pin, up to a total of 200 mA for the entire device. See the Absolute Maximum Ratings section. Any more current risks permanant damage of the device.

     

    -Ryan

  • 0 in reply to C. Ryan Land
    Prodigy 20 points
    Thanks Ryan! That's what I needed.
    Matt
  • 0 in reply to CurtissHawk
    Prodigy 40 points
    Dear Matt and Ryan
    I want use the same SN74AC14 or similar CD74AC14 or SN74ACT14: all AC series, change only temp.range, TTL in or not...
    My question is the following.
    The inputs have internal clamping diodes or not?
    I want use one of them to convert sine input signal to square output signal.
    Clear, if they have clamping diodes I must use an esternal resistor in series before the input to limit the current (i.e. 10k).
    So I can fed a input signal with amplitude more than the +5V (suppose it is my power supply) and obtain the conversion.

    I'm sure the 74HC14D have internal clamping diodes but I'm nor sure for these ICs.
    Best regards
    Gigi