This question is software related. I just wanted to know if it was possible to get the time at which my circuit reaches a certain value without just running the cursor and getting a approximate value. For example if I have a RC circuit , plot the time at which the voltage across resistor reaches 1/2 * Vdd. Is there someway to do code it and get the exact answer? if yes can you please explain how it can be done?

  • \$\begingroup\$ Yes, it's called circuit analysis. For simple circuits- you can derive an equation representing the time domain response; then simply solve that equation for your conditions, e.g. time at Vout = Vdd/2. \$\endgroup\$
    – user16324
    Commented Jun 30, 2021 at 16:37
  • 2
    \$\begingroup\$ For sure you can do it try to read here ltwiki.org/LTspiceHelp/LTspiceHelp/… and here youtube.com/watch?v=GtRaEHhMeCE \$\endgroup\$
    – G36
    Commented Jun 30, 2021 at 16:44
  • \$\begingroup\$ Aagh? I want to get it solved with LTSPICE not pen and paper. From my simulation results I want to find the time taken to reach a certain point @user_1818839 \$\endgroup\$ Commented Jun 30, 2021 at 16:45
  • \$\begingroup\$ @HariKrishna What do you mean by "plot the time at which the voltage across resistor reaches 1/2 * Vdd"? A .TRAN simulation is done in a range of time, anything plotted will be a function of that whole timespan. Did you mean that you wanted your simulation to stop when it reaches that value? Otherwise, this might help. \$\endgroup\$ Commented Jun 30, 2021 at 16:54
  • \$\begingroup\$ You want to use the .measure statement to automate such measurements. You should be able to search for examples using that keyword. \$\endgroup\$ Commented Jun 30, 2021 at 17:26

1 Answer 1


Use a .meas statement.

.MEAS TRAN res4 FIND V(out) WHEN V(x)=3*V(y) rise=last

Print the value of V(out) the last time the condition V(x)=3V(y) is met when approached as V(x) increasing wrt 3V(y). This will be labeled res4. Source: LT wiki

If I wanted to find the time when a node was at 0.5V, I would use a statement like this:

.meas TRAN newsignal2 FIND time WHEN 0.5=V(vout)

The results will show up in the spice error log, also if it says "Measurement [nameofsignal] FAIL'ed" that means the statement didn't find anything OR the syntax is wrong so this can make it difficult to debug.


Not the answer you're looking for? Browse other questions tagged or ask your own question.