LM7171: Simulation with LTspice

Joseph Magniez

Prodigy 30 points

Part Number: LM7171

Hi,

I downloaded the spice model provided of the LM7171 and would like to make a simulation using this part in LTspice.

The model provided do not work with LTspice.

At first I had to modify a little bit the format of the file so that LTspice recognize the PIN names.

It allow me to run a simulation but the results are not possible. It show a huge current consumption from the positive voltage supply and the non inverting input (a hundred amp).

My circuit is a very simple follower one, any Opamp would work like a charm for that.

Hereafter an overview of the test simulation and the simulation file and library that I use.

LM7171 test simulation.7z

Thank you in advance for your help.

over 5 years ago

0 Jacob Freet over 5 years ago

TI__Expert 8130 points

Hi Joesph,

Unfortunately I cant comment on the specifics of using one of our models in LTSPICE. However, in general if you are having pin assignment issues, it is a good idea to check the pin assignments in the LM7171 spice file as listed below.

3 2 4 5 6
+IN -IN V+ V- OUT

Regards,

0 Joseph Magniez over 5 years ago in reply to Jacob Freet

Prodigy 30 points

Dear Jacob,

I understand that you are not supposed to provide support for a competitor's simulator.

Nevertheless, this spice model is the code version of an equivalent circuit.

Can you provide me a screenshot of this circuit so that I can make one by myself?

For the pin assignment I actually took care of that but it seems my symbol and the spice model have a coherent pin assignment because I tried to rename the pins (2, 3, 4, 5, 6) with mode easy to read names (Inp, Inn, Vp, Vn, Out) and the simulation results were exactly the same.

Thank you in advance for your kind support.

Best regards,

Joseph

0 Michael Steffes over 5 years ago in reply to Joseph Magniez

Guru 48395 points

Of course Joseph there is a lot of info on importing models into LTSpice, like this

http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_4.htm

Quite a few youtube videos as well,

There is also a very large LTSpice users group on Yahoo that might help,

https://groups.yahoo.com/neo/groups/LTspice/info?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAF5qzmtQR1_eExHHqpXOTKRSn_cWitVVu3yeOi1EYWHjaJ0VLEcJxvqGyD6wPHtkwZcmhIrJs5w5aorYsfrZCgvKTqggNJ2ZpJ2c7dQFLmY9VEpJ6kRcgabqwmaIwZ_zd1iCp-Zxev3w-q50UBGOKqoWc_QRHmSAWiPjSuzEZNab

But really,TINA is easier.

0 Paul Grohe over 5 years ago in reply to Joseph Magniez

TI__Guru 53826 points

Hello Jacob,

I know this model works with LTSpice.

Remember, it is the *order* of the model .SUBCKT header nodes, not the names when importing to the simulator. Just renaming the nodes does NOT change their function.

Randomly renaming the header names within the .MOD file actually breaks the node links within the model. So DON'T do that. Replace the .MOD file with a fresh one if you edited it.

Make sure the Pin Order is correct in the symbol Pin Table.

In order from 1 to 5, it should be: IN+, IN-, V+, V-, OUT. Make sure the "Name" (the symbol pin name) matches the "SpiceOrder" (node position in the model .SUBCKT header).

0 Joseph Magniez over 5 years ago in reply to Paul Grohe

Prodigy 30 points

Hi Paul,

Thank you very much for your help. It seems my problem was really only due to the pin order as you mentioned.

Now I am able to simulate TI's ICs :)

Sincerely,

Joseph

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LM7171: Simulation with LTspice