LM317A: Iadj Adjust Pin Current Not Modeled in Spice Model

Stephen Savulak

Part Number: LM317A
Other Parts Discussed in Thread: LM317,

I noticed that the ~50uA Iadj current out of the ADJ pin is not modeled in the LM317A (or LM317) PSpice model. This noticeably affects the regulated voltage in my design. Has anyone edited the model to include this, or perhaps know of an LMx17 equivalent SPICE model that does model the ADJ pin current?

8 months ago

0 Stephen Ziel 8 months ago

TI__Mastermind 35505 points

Hi Stephen,

The Iadj pin current is not modeled in the TI LDO model. If I remember correctly, the PSpice model editor does include this in its generic LDO model, and you can try using that tool if you need the Iadj pin current modeled. I think the PSpice model editor tool uses a JFET or BJT to emulate the Iadj pin current, which would be the correct option in my mind for convergence and accuracy.

Thanks,

Stephen

0 Stephen Savulak 8 months ago in reply to Stephen Ziel

Prodigy 50 points

Thanks. Unfortunately I don't have access to PSpice.

+1 Stephen Ziel 8 months ago in reply to Stephen Savulak

TI__Mastermind 35505 points

Hi Stephen,

You can download a free copy of PSpice on TI.com website:

https://www.ti.com/tool/PSPICE-FOR-TI?utm_source=google&utm_medium=cpc&utm_campaign=asc-lamps-null-58700007787299765_PSpice_rsa-cpc-evm-google-wwe_int&utm_content=PSpice&ds_k=PSpice&gad_source=1&gclid=EAIaIQobChMIq_27jtG4hQMVJTbUAR14cQXWEAAYASAAEgJz9fD_BwE&gclsrc=aw.ds

Thanks,

Stephen

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LM317A: Iadj Adjust Pin Current Not Modeled in Spice Model