Re: CD4000 test
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Gentlemen, those CD4x and 74HC libraries have two required values that appear on a symbol's SpiceModel line.
ctrl-right-click a logic symbol to alter its SpiceModel line.
By default the two values are the nodes "VDD" and "0".
Creating a 12V power supply for CD4x logic and naming its output node VDD works out-of-the-box.
But assume for example, you already have a V-24 node and a V-12 node that could power the logic.
Change the logic symbol's default SpiceModel value from "VDD 0" to "V-12 V-24".
This sets logic outputs to be V(V-12)=logic-high and V(V-24)=logic-low, instead of VDD/0.
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In either case the difference across the power pins is 12 volts, -12 to -24 volts or 12 to 0 volts has the same 12 volt difference.
To power the internal logic from 12 volts, change the symbol's default SpiceLine (not SpiceModel) value from VDD=5 to VDD=12.
The SpiceLine VDD=x value sets the model's power-pin voltage and can be anything like VDD=2.3 or 3.5, 6, 12 etc...
The three SpiceLine values control functions within the logic like, prop-delay, output drive, slew rate, etc...
The SpiceLine SPEED=1.0 and TRIPDT=5e-9 are defaulted for the logic family.
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Changing the VDD=x value affects the speed of a given device. (i.e. CD4x is much faster at 15V than it is at 5V)
The SpiceLine SPEED=1.0 value is relative.
To model CD4x-like logic at 12 volts that is 10 times faster than normal CD4x logic, change the SpiceLine SPEED=1.0 value to SPEED=10.
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All for now
? Sent:?Wednesday, April 02, 2025 at 12:52 PM
From:?"Andy I via groups.io" <AI.egrps+io@...> To:[email protected] Subject:?Re: [LTspice] CD4000 test On Wed, Apr 2, 2025 at 12:38 PM, DerekK wrote:
Your voltage source V2 drives node VDD1.? ?That? should be node VDD.? ?These CD4000 models require a power node named "VDD". ?
Andy
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eewiz