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LM311: capture 13V signal

Allen Lu
Intellectual 2130 points
Part Number: LM311
Other Parts Discussed in Thread: LM2903

Hi Team:

 My customer want to use LM311 to capture 13V pulsed quadrature signal for MCU to detect high / low .

 If the ref voltage for LM311 is 6.5V,  does it work with single power supply 15V?  The reason why customer choose LM311 is their Propagation delay time is low as 0.115us,or do we have another recommendation? 

tks !

Here attached the customer waveform when we use LM2903:

 blue one is 13V pulsed quadrature signal(<10Khz) ,yellow one is the square wave signal that MCU need. But too much spurs currently.

 

  • +1
    TI__Genius 11701 points

    Hi Allen,

    Thanks for reaching out. The input signal is a bit noisy so I would add some hysteresis to reduce the chatter that you are seeing on the output. Yes, LM311 would work with a 15V VCC single supply but just keep in mind that the input voltage range is limited to +0.5 to 13.5V. Are you using the balance and strobe pins? Do you need the ground shifted output?  It would be helpful if you could show your schematic.

  • 0
    Guru 140200 points

    Hi Allen,

    what shall be detected? Only the triangle wave? As Chi already suggested hysteresis has to be added. But the superimposed noise which can be seen on the left of scope plot is so high compared to the triangle wave's amplitude that the hysteresis must be set very high.

    To suppress the superimposed noise and to ease the triggering of comparator some low pass filtering in front of the comparator may help.

    Kai

  • 0 in reply to kai klaas69
    TI__Genius 11701 points

    thanks kai that is also a good idea. 

  • 0 in reply to Chi Nguyen1
    TI__Intellectual 2130 points

    Tks all for these recommendation.