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Re: Simulation runs very slowly: test.asc

 

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I fixed all the anomalies in the TI LM317A model, so there are no errors or warnings. I also implemented the small changes in PSRR.

The reason your 2 circuits deliver different results is that 2nd one isn't functioning properly due to the current source I1. This causes the ADJ pin to go below ground and the O/P pin to reach 353mV. I added the LOAD parameter to spec of I1 - this prevents non-physical behaviour.

The analysis runs instantaneously in XVII, 24.0.12 and 24.1.5. Check that you have reset you SPICE parameters to default.

Try my upload: ProgCurrSource_corr_ATC.zip

Note:
  1. Symbol modified to remove hard-coded ModelFile attribute.
  2. Modified TI model to remove errors and adjust PSRR to match datasheet.
  3. Also, it is now possible to plot the dissipation of the LM317A. Previously, this was not possible because the ADJ pin had no internal termination.
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Regards,
Tony

On 06/04/2025 15:57, Christopher Paul via groups.io wrote:

Thank you, Tony.

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Here¡¯s the problem I encountered with the unmodified LM317A_TRANS while hoping to use the DC current source I1 to create a programmable current source. See ProgCurrSource.asc.

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The drop across Rc leaves only 12.5mV across Rs, leading to a 10mA current through RL. There are no AC currents flowing through either ADJ or through Rc, and there is no DC current through ADJ.

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The PSRR at the OUT2 terminal below 100Hz is a measly 25dB. At OUT1, the same PSRR is 55dB.

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With LTspice 17.1.14, simulating with .ac dec 100 10 10000 yields the following errors, although it also obviously produces the above results:

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Questionable use of curly braces in "b¡ìe_abmgate yint 0 v={if(v(a)>{{vthresh}},{{vdd}},{{vss}})}"

??? Error: undefined symbol in: "if([v](a)>((vthresh)),((vdd)),((vss)))"

Questionable use of curly braces in "b¡ìe_abmgate yint 0 v={if(v(a)>{{vthresh}},{{vdd}},{{vss}})}"

??? Error: undefined symbol in: "if([v](a)>((vthresh)),((vdd)),((vss)))"

u2:_u1_u12:dd1: Emission coefficient, N=2.6437e-312, too small, limited to 0.1

u2:_u1_u11:dd1: Emission coefficient, N=2.6437e-312, too small, limited to 0.1

u1:_u1_u12:dd1: Emission coefficient, N=2.6437e-312, too small, limited to 0.1

u1:_u1_u11:dd1: Emission coefficient, N=2.6437e-312, too small, limited to 0.1

Direct Newton iteration for .op point succeeded.

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