• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 19 subscribers
  • Views 101 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74AHCT14: SN74AHCT14N, SN74LS14N

RAMKUMAR R
Prodigy 50 points
Part Number: SN74AHCT14

Tool/software:

Hi TI,

We are looking the drop in replacement for DM74ALS14N(Fairchild semiconductor), During the checking we found the SN74AHCT14N and SN74LS14N parts(TI) as alternates.

During the datasheet verification i found the difference in the logical symbol between the actual and alternate parts.

 DM74ALS14N symbol and function table below

 

SN74AHCT14N,symbol and function table below

SN74LS14N symbol and function table below

Questions:

1. There is a difference in the symbol, and the symbol indicates whether the IC is an inverting or non-inverting Schmitt trigger, correct?


2. As per my understanding, the DM74ALS14N is an inverting Schmitt trigger, while the Texas part is a non-inverting Schmitt trigger, right?


3. According to the datasheet table, both perform inverting functions, but the symbols are different(DM74ALS14N is having inverting Schmitt trigger and Texas part are having non-inverting Schmitt trigger symbol). Can we consider the Texas part as a replacement?

Thanks,

Ramkumar R

  • 0
    Guru 316780 points

    1. The Fairchild symbol shows falling edges, which indicate an inverting buffer. But the bubble at the output also indicates inversion, so it is not clear whether there are one or two inversions.

    2. All parts are inverting buffers with Schmitt-trigger inputs.

    3. The TI parts can replace the DM74ALS14N. Some electrical characteristics might be different.

  • 0 in reply to Clemens Ladisch
    Prodigy 50 points

    Hi Clemens,

    Thanks for the clarification. There is no difference in the bubbles usage between Fairchild and TI parts. my doubt is the TI part show the non inverting symbol right, Then it needs to do only Schmitt-trigger function and no need to happens inversion right?. below is the reference. 

  • 0 in reply to RAMKUMAR R
    Guru 316780 points

    TI shows the bubble for inversion, and the part does inversion. The function table is correct.