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SN74ACT374: Allowable power dissipation

K.Hamamoto
Guru 12155 points
Part Number: SN74ACT374

Hi

Could you provide us the allowable power dissipation and max Cout?

In my understanding , the total power consumption is calculated by static power consumption and transient power consumption and capacities-load power consumption.

And under a specific condition, that max power will be calculated until max junction temperature. Is my understanding correct?

If it so, I can refer the following application note.
On the other hand, how can calculate the max Cout?

Best Regards,

Koji Hamamoto

  • 0
    TI__Guru* 96641 points
    Hello Hamamoto-san,
    The maximum power dissipation of the device can be easily found with the package thermal impedance and the maximum junction temperature --- for example, for the PW package, 83°C/W, assuming operation at the maximum ambient temperature (85°C). The max junction temperature is 150°C, so we can calculate maximum power dissipation (at 85°C operation for the PW package) here:

    (150 - 85) / 83 = 783 mW


    As for Cout -- are you referring to the output pin capacitance measurement or the maximum load capacitance?
  • 0 in reply to Emrys Maier
    Guru 12155 points
    Hi Emrys-san,

    Thank you for your reply.
    I understood about power dissipation.

    Regarding to Cout, I would like to know how can we calculate the maximum load capacitor.

    Best Regards,
    Koji Hamamoto
  • 0 in reply to K.Hamamoto
    TI__Guru* 96641 points

    Hamamoto-san,

    Thank you for the clarification.

    We typically recommend keeping the load to less than 70pF, however this is not a hard requirement.

    The maximum load capacitor is a tricky subject -- there is technically no limit, however you will see diminishing output edge rates with larger capacitors and increased power consumption. Additionally, at some point (as C approaches infinity) you will essentially be driving constant current out of the device that exceeds the device's maximum rating.

  • 0 in reply to Emrys Maier
    Guru 12155 points
    Hi Emrys-san,

    Thank you. I understood.

    Best Regards,
    Koji Hamamoto