Hello:

Could someone tell me where I can find 74HCT640 model for LTspice?

Thanks!

 

Hello:

Could someone tell me where I can find 74HCT640 model for LTspice?

Thanks!

You can make a behavioral model and put it in a subcircuit. Would that work for you?

 

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.

 

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:

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.

 

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

 

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.

 

Hi papa,
Many thanks, these are my 74LVC sims, looking OK.
E

@zeros

 

Hi papa,
Many thanks, these are my 74LVC sims, looking OK.
E

@zeros

Props Eric. You got the hang of that library pretty quickly.

 

A tristate bidirectional buffer could also be modelled using the standard 'A' devices in the LTS Digital folder :

 

Hi Alec,
I have done a similar circuit, but the HC640 is an Inverting bidirectional, so you need to modify the Ax outputs to inverting.
E

 

Hi

74HCT640_Test.zip contains Model, Test circuit and symbols.

 

you need to modify the Ax outputs to inverting.

I was modelling a general-purpose non-inverting type rather than the HCT640 specifically, but yes, just use the inverting outputs of A2 and A3 if modelling the '640.

 

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