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LTSpice woes: oscillation and logic controls

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ACharnley

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As much as I love this software I equally hate it.

Working with FETs and voltages I find myself more and more using GPIO's to make decisions, which requires emulating the hysteresis logic they'd contain otherwise LTspice goes into loops. Unless I'm missing a trick I end up doing multiple B source's which reference one another. The approach works but after a while the multiple IF's become a pain (I sometimes have 4!).

Surely there's a better way?!?

Q) Is it possible to set params dynamically?
Q) Is it possible to condense these IF's using standard operators: && ||


Screenshot_2018-09-04_09-05-41.png
 

rjenkinsgb

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Most Helpful Member
Does it have emulations of single schmitt triggers such as 74HC14, CD40106 etc?

Depending what you are doing, they may work.
 

alec_t

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Have you tried using the 'A' devices? You can set their parameters (e.g. you can set the Schmitt buffer threshold and hysteresis, so that it behaves like a comparator), but AFAIK you can't set any parameters dynamically.
 

alec_t

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They're in the LTS 'Digital' folder and are primitive ideal gates with 1V logic by default.
 

alec_t

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alec_t

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Don't think that's possible. Try using a pair of gates or switches.
 

eTech

Active Member
alec_t, bingo - that's exactly what I needed.

Now, how to get the schmitt inverse pin to include a deadzone?
The A devices don’t support that functionality. You’ll have to use a combination of A devices.

Maybe use a clock source with a leading and trailing edge detectors. The pulse width of the clock source could then set the “dead” time.

eT
 

alec_t

Well-Known Member
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Here's one way :
Deadzone.PNG

Param 'on' sets the dead zone between b and d.
 
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