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CD74HC165&CD74AC14

Expert 2750 points

Replies: 3

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1)Dear Sir, please answer. I'd like to use CD74HC165 register with 3.3V supply and I need to connect Q7 output of  the CD74HC165 to the  input of  CD74AC14 (3.3V supply too). I will not have problems with this? 

2) If I use 74AC series at 5V supply, then I can load output pin at 20 mA source current.   If I use 74AC series at 3.3V supply, then can I load output pin at 20 mA source current (output pin in HIGH level and current flows from IC to GND via resistor) ?

TIA

Sincerely

Vladimir Naumenkov

www.agat.by

  • CMOS outputs and inputs are compatible.

    The Schmitt trigger is not needed here, but I guess you want it for some other inverter.

    Instead of the inverter, you could simply use the inverted output of the '165.
  • In reply to Clemens Ladisch:

    Dear Clemens, Thank you

    Please see my question #2, a added it later.

    Please, answer.  I need to transmit logic signals from outputs of register 74AC164 via wire 40-50 centimeters ( I use flat cable), then will I need to install after  74AC164  bus transceiver  as 74AC623 or another?

  • In reply to Vladimir Naumenkov:

    As shown in the "electrical characteristics" table, the output drive at 3.3 V is 12 mA/−4 mA with the specified voltage drop. You can get more current if you can live with a larger voltage drop.

    Whether this is enough for the ribbon cable depends on how noisy it is.

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