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Part Number: SN74AHCT244
I have a question for SN74AHCT244 output current for capacitive load.
The datasheet(SCLS228M) defines absolute max of “Continuous output current, Vo<0 or Vo>Vcc)” as +-25mA.But in my customer’s system, the peak output current is around +-78mA due to 0.01uF capacitance of RC filter while it is very short time.The below is the circuit and waveform.Does the customer have to keep this continuous output current, +-25mA, even if the time over 25mA is less than a few us like this figure? Does they need to adjust RC filter parameter to keep the peak current less than +-25mA?
We recommend keeping the output load capacitance at or below 70pF. If larger capacitances are to be used, a limiting series resistor should be added to keep the maximum current below 25mA.
In this case, the 51 ohm resistor should be swapped for a 220 ohm resistor to keep the maximum current (assuming a 5V supply) below 25mA.
If this is a filter circuit, the capacitor value can be adjusted to keep the same cutoff frequency.
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In reply to Emrys Maier:
Thanks for your answer.Where does "70pF" come from? I can't find any description about it in the datasheet.Regards,Oba
In reply to Oba:
This is a recommendation from the standard logic applications team, not a set value in the datasheet.
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