TL331B-Q1: Circuit Review and Simulation Inquiry

Siddh Patel

Part Number: TL331B-Q1
Other Parts Discussed in Thread: TL331, TL331LV, LM339

Tool/software:

Hello,

I am trying to simulate a simple comparator circuit in Altium designer. I have attached the design and simulation output. The voltage source v11 does a dc sweep from 1.6 to 3.2V. The threshold voltage is 2.84.

I am not sure why that peak if happening after it switches from high to low then settles at 2.5V.

2 months ago

0 Paul Grohe 2 months ago

TI__Guru 60526 points

Hello Sidith,

You are violating the input range. The TL331 has an input range limit of VCC-2V, or 3V max on a 5V supply.

The model has a feature that forces the output to Vcc/2 when there is an input violation.

Note the "error" occurs right at 3V.

You must re-adjust your input range to stay below 3V, or, use a TL331LV that has a rail-to-rail input.

For more info, please see section 6.4 of the LM339 family appnote:

Application Design Guidelines for LM339, LM393, TL331 Family Comparators

0 Siddh Patel 2 months ago in reply to Paul Grohe

Prodigy 30 points

Is this violation for just the simulation or will it happen in real life too?

0 Paul Grohe 2 months ago in reply to Siddh Patel

TI__Guru 60526 points

See section 6.7 of the appnote - the "Feature"..

The real device may work at room but will fail at cold.

It is up to you if you wish to rely on an un-guaranteed "feature".

0 Siddh Patel 2 months ago in reply to Paul Grohe

Prodigy 30 points

Sounds good, Thank you very much for your help.

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TL331B-Q1: Circuit Review and Simulation Inquiry