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Original question:

TLV1872: Maximum input signal frequency

TLV1872: Long and varied propagation delay with 50Hz sine wave

Henry Chen43
Prodigy 20 points
Part Number: TLV1872
Other Parts Discussed in Thread: TLV1805

Tool/software:

Hello,

       We are trying to convert a 50Hz, -5V to 5V sine wave to the corresponded  0V to 3.3V square wave with TLV1872. After simulation, we found something interesting and would like to consult with you experts.

       First, the propagation delay is as long as about 500us which is thousand times longer than the spec.

       Second, the propagation delay varies over the waveform cycles; the deviation is as much as 1ms.

Is there any slew rate or frequency limit to its input? The threshold (reference voltage) is set to 0V.

It's kind of you to help.

Best Regards

Henry

  • +1
    TI__Genius 11315 points

    Hi Henry,

    Any way you can share with me your simulation file? Usually, discrepancies in the propagation delay can be attributed to the timestep of the transient sim.

    Please try going to "Analysis" -> "Set Analysis Parameters" and change the max timestep to 1ns:

  • 0 in reply to HO SIU
    Prodigy 20 points

    Hello Ho,

          Thanks for your prompt response. After changing the analysis parameters accordingly, the discrepancy in the propagation delay did disappear! Although the simulation time increases a lot from several seconds to ten's of minutes. We tried to simulate with another comparator TLV1805 under the same default parameters but found little deviation of propagation delay. These results are interesting and it's kind of you to let us know the difference if possible.

    Thank you for your help again.

    Best Regards,

    TLV1872.TSMHenry

  • 0 in reply to Henry Chen43
    TI__Genius 11315 points

    Hi Henry,

    Yes, the simulation time increased due to the lower maximum time step. This is because if you lower the time step, the waveform will have more points: number of points = data saved simulation time / time step.

    I'm not too sure what's causing the discrepancy between the TLV1872 and TLV1805 simulations, and it's hard for me to tell with just the waveform screenshot. Could you please share with me the .TSC file schematic instead of the TLV1872.TSM macro?

  • 0 in reply to HO SIU
    Prodigy 20 points

    Hi Ho, 

        My bad! Please refer to the attached .TSC file. I downloaded it from TI's product website and modified he input waveform to sine wave at 50Hz. There's nothing else in the simulation schematic. I thought the problem is solved and thank you for your help again!TLV1872.TSC

    BRs

    Henry

  • 0 in reply to Henry Chen43
    TI__Genius 11315 points

    Hi Henry,

    I thought there was a further issue that you were experiencing with the TLV1805. It seems like the issues have been resolved. I'll be closing this post.

    Regards,

    Ho