After struggling with SPICE models on and off for awhile (over a year ) here's something that might be useful for some folks that are attempting a frequency to voltage conversion; a tachometer for instance.

You can use the attached with the free LTSpice, a product of Linear Technology. Google is your friend here. I'm not going to be much help porting this to other Spice versions, so don't bother asking - you're on your own.

It's a macromodel, not a component model. However, it covers the following IC's:
LM2907-8
LM2907-14
LM2917-8
LM2917-14

It's based off Russ Kincaid's macromodel for the LM2907-14, which disappeared from the Internet not long after I downloaded it.

Your mileage may vary; however the model/simulations may prove useful as a starting place.

The .sub file belongs in:
\Program Files\LTC\LTSpiceIV\lib\sub
The .asc files go in:
\Program Files\LTC\LTSpiceIV
The .asy files go in:
\Program Files\LTC\LTSpiceIV\lib\sym\misc

The basic macromodel that Russ published is:

I rotated, re-sized and converted his original work to .PNG format.

 

I know it's kind of obvious, but anyway, where you said .sym I think you meant .asy, also with LTSpiceIV (downloaded today), it's C:\Program Files\LTC\LTSpiceIV.

Just in case anybody can't figure it out.

Thanks very much for the models!

 

Thanks for the update; my LTSpice installation has been updated numerous times, but I've had it installed for a couple of years (since SwitcherCadIII) - it doesn't update the directory name when getting the latest upgrades.

Good catch on the .sym vs .asy filename extension - can you tell that I was tired?

 

Thanks for the update; my LTSpice installation has been updated numerous times, but I've had it installed for a couple of years (since SwitcherCadIII) - it doesn't update the directory name when getting the latest upgrades.

Good catch on the .sym vs .asy filename extension - can you tell that I was tired?

LOL Thanks again

 

Is it reasonable for me to use LTSpice (and these models) for component (R1,C1,C2) selection when using a 2917 ?
I am trying to use the part (lm2917) in a circuit which is to work in the range of 5Hz to 45Hz, and I am seeing that the output (in LMSpice) is very "ripply". I am using your resistor/capacitor output filter thingy to help with this, and that is helping smooth out the output somewhat, but it's still a ripple.

I have ended up with values of:
C1 = 20nF
C2 = 0.1uF
R1 = 470k
R2 = 10K

but no matter what, it looks as though low frequencies like 5Hz are not very friendly with this circuit ? Any ideas?

Also I am seeing that C2 has a huge effect on the peaks of the output voltage (e.g. with the above, the voltage at "Out" seems to peak at 820mv, whereas if C2 is changed to 0.01uF (1/10th previous value), then the voltage at Out peaks at 7v.., even though C2 is barely if ever mentioned in the specification of the part).

 

Carl0s,
My original thought with creating these models is that people would want to use them for tachometer accessories. A normal auto engine might idle at 550 to 800 RPM. Even a 4-cylinder engine would likely have an idle tachometer output at around 20Hz or so.

The filter example between Out and Out2 - try making two filters in series by adding another resistor and capacitor. You will see the ripple decrease quite a bit more.

The model is not completely accurate. There is a note in the model Russ had added to it; the real part saturates at roughly Vcc/2 but this model does not.

 

Carl0s,
My original thought with creating these models is that people would want to use them for tachometer accessories. A normal auto engine might idle at 550 to 800 RPM. Even a 4-cylinder engine would likely have an idle tachometer output at around 20Hz or so.

The filter example between Out and Out2 - try making two filters in series by adding another resistor and capacitor. You will see the ripple decrease quite a bit more.

The model is not completely accurate. There is a note in the model Russ had added to it; the real part saturates at roughly Vcc/2 but this model does not.

Thanks very much for your advice again. It seems I had mis-understood the tach output frequency and you are right, it's 2Hz for 60rpm, so as you said 20Hz = 600rpm, so my circuit actually needs to deal with 20Hz to 160Hz, and everything looks fine now!

cheers,
Carl