74HC112 ltSpice problems.

Thread Starter

Domophone

Joined Sep 10, 2013
65
I cannot figure out why my 74HC112 model is not working. The subckt is part of the yahoo group 74HC library (Revision 0.59 03/29/2005 ).

is this an issue with my 74HC library or am i missing some key insight?
Here is my output of the simple test circuit: 74hc112_no-output.JPG
and the relevant part of the 74HC.lib file: 74hc112_no-output2.JPG
 

Alec_t

Joined Sep 17, 2013
15,117
Try connecting the preset and clear inputs to +5V. Unused inputs of CMOS devices should never be left floating, or strange things can happen. Also, give the clock rise and fall times a finite value.
 

MisterBill2

Joined Jan 23, 2018
27,507
Try connecting the preset and clear inputs to +5V. Unused inputs of CMOS devices should never be left floating, or strange things can happen. Also, give the clock rise and fall times a finite value.
Exactly so!! It might work with TTL but it will never work well for CMOS. Also, ground all of the unused inputs on the other half of the IC.
 
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