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  1. #1
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    uvlo circuit

    If there is no Zener diode devices,How to design undervoltage lockout circuits?


    Best regards,

    •   Alt8th November 2004, 13:54

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    undervoltage lockout

    most times uvlo simply uses a comparator with a little hysteresis. VDD is divided down (say in half), and compared to the bandgap voltage. (Say 1.25v) Now your uvlo trips when VDD = 2Vbg or 2.5v. There ya go.

    Do you have a bandgap? If not it's a little trickier..



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    undervoltage lockout circuit

    I also suggest you use a simple comparator .use devided Vdd compared with a stable reference.it must need a reference voltage.



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    under voltage lockout circuit

    qutang - please don't repeat answers, or post junk. it really bothers me.



    •   Alt9th November 2004, 17:26

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    under voltage lockout

    Quote Originally Posted by electronrancher
    most times uvlo simply uses a comparator with a little hysteresis. VDD is divided down (say in half), and compared to the bandgap voltage. (Say 1.25v) Now your uvlo trips when VDD = 2Vbg or 2.5v. There ya go.

    Do you have a bandgap? If not it's a little trickier..
    Hi, what if the supply voltage drops to a level that both bandgap and comparator are not able to work, at this moment, the output signal is uncertain, it will be 0.6v or something like that, so how to make sure when VDD drops (under 2Vbg in your case), the UVLO circuit can give a reliable 0V output? Thanks.



    •   Alt7th December 2004, 01:26

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    undervoltage lockout ic

    hi,cmosbjt

    you can use pull up Res to fit your request



  7. #7
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    circuit under voltage lockout

    you need a "UNDERVOLTAGE SENSING CIRCUIT". you could use an IC like MC34064. i advise you to check spec sheet of MC34064.

    -Erkan



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    under voltage lock out

    how can i do if for high voltage?if i dont' want to waste so much current the voltage divided, another method?as long as i don't want to draw a big resistor in my IC also
    thanks



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    under voltage circuit

    up to about 12v, i usually see resistor dividers of a few hundred k. other alternative is if you have an internal regulated supply voltage, do uvlo on that rather than on the input.

    what is your uvlo voltage you want?



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    12v undervoltage ic

    I don't see how you can do away with some form of potential divider. it can be resistor/mos. use natural mos for higher thresholds.



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    supply undervoltage design

    How can i include hysteresis?
    Is it sufficient to introduce hysteresis in comparator? or i have to introduce it externally?

    If externally, how to include it?



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    Re: Looking for undervoltage lockout circuits!




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