I need help setting up the 74LVC1g74 Flipflop parameters for 5V operation.

From the 74LVC1G.lib file I get the following information:

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* Delays have been adjusted for Vcc = 1V8/2V7/3V3/5V (LVC) using the test conditions stated in the
* Nexperia data sheets, and generally achieve Tpd errors less than 10%. The actual VCC voltage needs
* to be passed to each device as a parameter, either a fixed value, or a variable by placing:
*
* - VCC={VCC} Speed=1 Tripdt=100p
*
* in the Value field of the symbol, where {VCC} denotes that it is defined somewhere in the schematic.
*
* Temperature effects are currently not modelled.
*
* https://www.nexperia.com/products/analog-logic-ics/family/LVC/#/p=1,s=0,f=,c=,rpp=,fs=0,sc=,so=,es=

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Do I use Speed=1 for 5V operation?  What do I use for Tripdt value?  What does Tripdt=100p mean?

 

Your help will be much appreciated.  

Thanks, 

Jim

Oops, I meant to say "74LVC1G74.

 

Jim

 

On Mon, Dec 30, 2024 at 07:03 PM, Jim McLucas wrote:

* - VCC={VCC} Speed=1 Tripdt=100p
,,,

Do I use Speed=1 for 5V operation?  What do I use for Tripdt value?  What does Tripdt=100p mean?

• Speed allows you to choose a relative speed variation.  Speed=1 is for a nominal (typical) part.  It is independent of VCC.  You might try values such as Speed=0.7 or Speed=1.5, for slow or fast parts.
• VCC is the power supply voltage.  With luck, the model already changes its speed depending on the value of VCC, independently of the Speed parameter.
• The Tripdt parameter is a helpful convergence aid for some of the internal devices inside the model.  It suggests to LTspice that it should throttle the internal timestep to 100 ps or less when the signal is changing.  This helps prevent LTspice from advancing right through a change of state (low to high or high to low).  It's unlikely that you would need to change that parameter.