Need 74HCT640 model in LTspice

Thread Starter

zeros

Joined Nov 27, 2023
26
You can make a behavioral model and put it in a subcircuit. Would that work for you?
Thank you for your response, Papabravo! I am familiar with the concept of subcircuits in LTspice, and I would appreciate if you could elaborate more on creating behavioral models.
 

Papabravo

Joined Feb 24, 2006
21,225
Thank you for your response, Papabravo! I am familiar with the concept of subcircuits in LTspice, and I would appreciate if you could elaborate more on creating behavioral models.
Well, from the datasheet of Texas Instruments we have the following diagram on page 1:
1704468789022.png
The logic libraries for the 74HC series have basic gates and tri-state inverters. From these existing parts you could create a subcircuit with the pinouts in the diagram and the functionality specified in the picture.
 

ericgibbs

Joined Jan 29, 2010
18,849
Hi papa'
With the intention of helping the TS with a hierarchical model of the hct640, I downloaded the Spice model for the CD74HC240, a supposed Tristate inverter.
Created a working model, but on testing it works as expected with the exception it does not go to a HiZ out state when not enabled. ??? ie: the output sinks current.

Do you have a fully working model of the 74HC240 that you could post?
E
 

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Papabravo

Joined Feb 24, 2006
21,225
Hi papa'
With the intention of helping the TS with a hierarchical model of the hct640, I downloaded the Spice model for the CD74HC240, a supposed Tristate inverter.
Created a working model, but on testing it works as expected with the exception it does not go to a HiZ out state when not enabled. ??? ie: the output sinks current.

Do you have a fully working model of the 74HC240 that you could post?
E
I do have the74LVC1G125 and 74LVC1G126 which are tristate buffers. I think you might need to take the entire 74LVC1G.lib since the parts are put together from quite a few pieces.

ETA: Here is what I got from the LTspice users group along with some custom symbols. These symbols do not have explicit power and ground connections. They rely on net names VCC and VSS to pick up power from the schematic.
 

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Last edited:

Alec_t

Joined Sep 17, 2013
14,314
A tristate bidirectional buffer could also be modelled using the standard 'A' devices in the LTS Digital folder :
1704637851213.png
 

Thread Starter

zeros

Joined Nov 27, 2023
26
Thank you so much for your help! I've managed to solve the problem perfectly with your guidance. It's really appreciated.
 
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