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Thread: Logic control exists in LDO

  1. #1
    alphacat Okay
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    Default Logic control exists in LDO

    Hello,

    Up until now I treated LDOs as black boxes which receive a certain voltage and produce constant (lower) voltage.

    I started reading a bit about its construction and I saw it uses a Logic control.

    What is this logic control for?
    And what is the device that the logic control feeds?

    Thank you.

    Last edited by alphacat; 26th October 2009 at 01:13 PM.


  2. #2
    speakerguy79 Excellent speakerguy79 Excellent speakerguy79 Excellent speakerguy79 Excellent speakerguy79 Excellent speakerguy79 Excellent speakerguy79 Excellent
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    Logic control is probably things like over-current and over-temperature limiting. Even very old regulators like the 7805 or 317 feature things like this.

    The rest of the circuit is just the analog feedback path that the logic control can disable. PMOS pass transistor, voltage comparator, internal voltage reference being compared to the voltage at the feedback/adjust pin.
    Last edited by speakerguy79; 26th October 2009 at 01:12 PM.

  3. #3
    ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent ericgibbs Excellent
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    Quote Originally Posted by alphacat View Post
    Hello,

    Up until now I treated LDOs as black boxes which receive higher voltage and produce constant (lower) voltage.

    I started reading a bit about its construction and I saw it uses a Logic control.

    What is this logic control for?
    And what is the device that the logic control feeds?

    Thank you.
    The logic is part of the ENABLE circuit, controlled from the Enb pin, to on/off the device.
    Eric " Good enough is Perfect "
    I will NOT answer PM's requesting technical help, please use the Forum
    PIC tutorials: Nigel's www.winpicprog.co.uk/ Bill's: www.blueroomelectronics.com/

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