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TINA/Spice/TL331-EP: TL331 PSpice model issue

Part Number: TL331-EP
Other Parts Discussed in Thread: TINA-TI, , TL331, TLV3401, TLV1701, TLV3011-EP, LM193, LM139, LM293-EP

Tool/software: TINA-TI or Spice Models


I am using TL331-EP for my design. I have downloaded Pspice model from TI Web.I am using TL331-EP for Comparator design with hysteresis.

My Comparator design is explained as below

  • For an input of 0V-4.5V it should provide high output.
  • For an input of 10.5V-49V it should provide low output.
  • Range between 4.5V-10.5V is covered by hysteresis.

My application requires supply Voltage of 3.3V to the TL331-EP.The simulation results are not correct with 3.3V power supply to TL331.

But if i change supply voltage to TL331 to 5V then it works satisfactorily.

As per the TL331 supply voltage range (2V-36V)it should work with 3.3V as well, so why i am facing the issue.

I am attaching my deisgn as well.

Thanks ,

Rahul Wagh

  • Rahul,
    The model was designed to work at a +5V power supply and it supports a specified list of specs at this voltage.
    You can see this in the Notes section of the model's netlist header, which is included below for reference.
    *1. The following parameters are being modeled at +5V operation:
    2. Response Time does not vary with input level, and is equal to
    approximately 700ns at +5V operation.
    3. This model is intended to work with single supplies, e.g. {+VCC,GND}
    4. This model is based on data sheet parameters for +5V operation.
    It is unknown if this model will match device behavior at
    other power supplies.
    Also, I don't see the project attached to this thread.
    Please let me know if you have any more questions.

  • Hi John,

    Thanks for the reply.

    As TL331 is rated for 2V-36V even though the model does not support for 3.3V supply voltage but the actual device should function at 3.3V.

    Could you please confirm that.

    I am attaching my design .

    Thanks & Regards


  • Rahul,
    According to the data sheet, the part works down to 2V, but many of the quoted specs are at 5V, 15V and 30V.
    If you have some concerns about the details of device behavior, I can move this thread to the E2E forum supported by the product experts.
    They will be able to address any questions you have.
    Would you like me to do that?
  • Hi John,

    Thank you.

    Ok, can you please move the query to product expert team.


    Rahul Wagh

  • Thanks, John!

    Hello Rahul,

    While the TL331 will function down to 2V, the valid input range restricts the usefulness at low voltages.

    You are violating the input voltage range (Vicr), and most likely the model is acting "strange" because is is supposed to.

    The TL331 is not a rail to rail input device. The legal input voltage range is 0V to 1.5V below V+, or 1.8V max on a 3.3V supply. At a 5V supply, the max input voltage would be 3.5V.

    The maximum voltage in the inputs is ~2.4V. The inverting input (pin 1) is greater than 1.8V when the input voltage is above 19V. At 3.3V, it is above the 1.8V limit, but at 5V supply, it is below the 3.5V limit - so it works correctly.

    You need to either:

    1. Use a higher supply voltage
    2. Use a R-R input device with input range to V+ (TLV1701, TLV3401, LMC7235, etc)
    3. Increase the division ratios to bring the input voltages below 1.8V

    I think option #3 is the easiest since the other mentioned devices have a different pin-out and would require a re-layout. Changing a few resistors is easier!
  • Hi Paul,

    Thanks for the solution provided by you!

    I am able to twik the design by changing the resistor values, which resolves my problem.

    As you said TL331 is not an rail to rail comparator hence i made my resistor values modified such that the input voltage to

    inverting or non-inverting terminal should be <1.8V at 3.3V Supply voltage.

    I have selected TL331MDBVTEP for my design as temperature grade requirement is -55DegC to +100DegC.

    As the other devices suggested by you which are rail to rail does not support the above required temperature range.

    even though i have got the solution to the problem by changing the resistor value, still if you can suggest a rail to rail comparator for the above temprature grade and 3.3V supply will be a back-up option for me.

    Thanks & Regards

    Rahul Wagh

  • Hello Rauhl,

    Glad you resolved the main problem.

    The main limiting factor is the -55°C temp as this puts it into the Military and/or "Enhanced Product" temp range. Military devices are usually not in plastic packages, and there are only a few 'Enhanced Product" devices in SOT-23. So they will not be cheap.

    The only other comparator in SOT-23 with a -55°C spec is the TLV3011-EP, but the pinout is different and 10x slower.

    Your greatest options will be to use the Dual or Quad in plastic SOIC-8 devices (LM139, LM193, LM293-EP and TLV3492-EP). Duals and quads have pretty standard pinouts and are easier to replace.