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SN74LVC04A: SN74LVC04A SN74AHC14 and SN74LVC14A about the VOH value

Part Number: SN74LVC04A
Other Parts Discussed in Thread: SN74LVC14A, SN74AHC14

Hi Team,

The customer needs to get the max  VOH value and the min VOH value for SN74LVC04A SN74AHC14 and SN74LVC14A.

The customer's requirements are when VCC is 3.3V and IOH is 1.5mA, what  are the max  VOH value and the min VOH value for SN74LVC04A SN74AHC14 and

SN74LVC14A?  I cannot see the value that the customer needs in the datasheet. Can you tell me these values?

Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments

  • The datasheets show values for 3 V because the power supply is assumed to be inaccurate. Does the customer really have 3.3 V ± 0.001%?

    Anyway, the output impedance is practically constant in the range of allowed currents. So without actual characterization information, you can derive the voltage drop at 1.5 mA from the voltage drop at the maximum current (and add a little safety factor, depending on how paranoid you are).
  • Hi Clemens,

    Thank you for your reply.
    Yes, VCC is 3.3V for the customer.

    Is there our engineers to see my issues?
  • Hi Mickey,

    Logic datasheets typically spec the worst case scenario for these values.  As Clemens implied, it's rare to see a supply rail that is _exactly_ 3.3V.  The LVC family of devices show the standard 3.3V rail minus ~10%, which is where the specs are the worst.

    V_OH is determined by drawing current from the device until it reaches a certain output voltage, then recording those values.  For example, on the SN74LVC04A, slowly increasing values of current were drawn out of the device operating at 3V while measuring the V_OH until it decreased by 20% (2.4V @ 25C), then the amount of current was recorded (14mA).  This is a 20% decrease in output voltage, which was apparently the threshold determined by the systems engineer for that test. 

    In reality, a logic gate rated to 14mA on the V_OH spec that is only driving 1.5mA will be outputting ~0.99*Vcc, however I can't guarantee that since it isn't in our datasheet.

    In summary, with a 3.3V rail, we can guarantee that the device will output a value higher than or equal to that given as the 3V V_OH value on the datasheet.