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LM317 Help

Discussion in 'Power Electronics' started by Dave Benemerito, May 30, 2018.

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  1. Dave Benemerito

    Dave Benemerito

    24
    0
    Sep 26, 2015
    Hi,
    I have a SIM800L module with no voltage regulator on it. I have power it between 3.7V to 4.4V. I was using LM317 to regulate the power from the supply (4.6 to 5V) using two resistors 220Ω and 470Ω
    Screenshot_20180530-220055.png
    When building the circuit, the output voltage was 3.1V which lower than recommended and might damage the module in my opinion
    20180530_215319.jpg
    20180530_214205.jpg
    I have never powered the module. I would like to ask help what to do before i could damage the board. Thanks! :)
     
  2. Chemelec

    Chemelec

    291
    47
    Jul 12, 2016
    You need to get an "LDR" Type of Regulator.
    LDR = LOW DROP OUT.

    The LM317 has too High of a Voltage Loss between Input and Output.
     
    Dave Benemerito likes this.
  3. dave9

    dave9

    837
    203
    Mar 5, 2017
    If the power supply is low enough ripple, just throw a silicon diode in series with it to drop ~ 0.7V
     
    Dave Benemerito likes this.
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