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TLV3201: TLV3201 output

Lei wang
Expert 1620 points
Part Number: TLV3201
Other Parts Discussed in Thread: TLV7011, TLV1805

HI Sir: this is my test circuit. When I  connect the PIN3 to GND . The output should be Low. But I find that When I power on.   there is  short high pulse. pls ref the picture. I want to know why?

     

  • 0
    Guru 140200 points
    Hi Lei,

    the minimum supply voltage of TLV3201 is 2.7V. But during power-on the supply voltage starts from 0V. So, therer's a brief period when the TLV3201 might not work as expected. This is absolutely normal. No OPAmp or comparator can properly work at a too low supply voltage.

    Kai
  • 0
    TI__Mastermind 49896 points

    Hello Lei,

    Assuming the scope vertical is 1V/Div, it looks like the supply voltage is between 1V and 1.2V with a fairly slow ramp.

    As Kai said, the minimum supply voltage is 2.7V, so the device is just becoming awake at 1V, but is not fully biased yet. 1.2V is about where the internal circuitry starts to wake-up but not fully biased. So the output "flops" as the supply votlage ramps up to the minimum supply voltage.

    What Kai said is <mostly> true, is that most comparators will glitch as the supply is ramped-up.

    HOWEVER, we have now been introducing comparatos with an internal POR circuit that minimizes this power-on "glitch" by requiring both a time and minimum supply voltage limit be met before the output starts responding to the inputs.

    Please see the TLV7011 or TLV1805 family of comparators. The fastest is 250ns, hopefully that is fast enough for you. The supply votlage must cross 1.6V and/or  power must be applied for 20us. The output will be low during this time.