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SN74LV4T125: Supply Current

Part Number: SN74LV4T125
Other Parts Discussed in Thread: SN74LVCH16T245-EP

Do I_CCA and I_CCB (pg. 5 of the datasheet) specify the input currents at the two voltage inputs or would that be a different value?

  • Hey Zachary,
    The datasheet for SN74LV4T125 doesn't mention ICCA or ICCB anywhere -- unless I'm missing something. Are you talking about a different part perhaps?

    Typically these values refer to static supply current -- ie the current into the A or B supply (respectively) when the device is holding a static value on the outputs.
  • Apologies, I was looking at the SN74LVCH16T245-EP datasheet. 

    I think what I'm really trying to get at is what are the input/output power limits on the device? Do I use the type of supply current you mentioned to calculate input power or something else?

  • Hey Zachary,

    When you say "input power" I'm not entirely sure what you mean.  You could be referring to supply power (ie how much power must be put into to the device to make it work) or you could be referring to the input signal power (ie the amount of power that the input requires to operate).

    For a logic device, the input signal power is practically irrelevant. The inputs are high impedance (typically >10 MΩ) and what matters is the voltage level at the input. If you wanted to know the power being consumed there, you could take the worst case leakage value (1 μA) and multiply by the maximum input voltage, 5.5V. That would give a peak "input power" of 5.5 μW.

    For supply power, you need to know a few more things (ie operating frequency, number of active channels, load impedance).  There's an application report that discusses how to calculate this in detail located here: CMOS Power Consumption and Cpd Calculation