Behavioral Current Source as an Analog Timer

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Joined Feb 24, 2006
The use of timers in digital and microprocessor circuits is common. Precise timing in analog circuits is less common, usually relying on RC circuits and such. In simulations we can use the behavioral current source or the behavioral voltage source along with mathematical functions to simulate precise delays with a simple component. In LTspice there is a function called "idt" which can integrate a constant current or constant voltage to produce a linear ramp effectively converting time to voltage. This ramp can then be used to create logic level signals where the edges have fixed time relationships to one another, The following LTspice simulation shows the implementation of both an On-Delay Timer and an Off-Delay Timer.




Joined Nov 13, 2020
It seems that everything old is new again.
Back in the early-1960's I was building instrumentation for the high-energy physics community. One popular product was the Time-to-Height converter. It's voltage output was then fed to an analog-to-digital converter and converted to time. The equipment was built completely out of discrete devices, and had sub nano-second (actually 10's of ps) time resolution. Pretty much pushing state of the art back then.