Selecting parts for the MC34063 buck regulator

Discussion in 'General Electronics Chat' started by spinnaker, Oct 28, 2012.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
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    I am looking to build a 12-5V step down buck regulator based on the MC34063.

    The regulator will power a 5V pic and lcd.

    I have seen a couple of datasheets and they say nothing (at least directly) about part selection while a datasheet for a current regulator PT4115 spells out part selection very clearly.

    First a question on resistors. What tolerance for the sensing resistor? Would 5% be OK?

    And for the caps? The pt4115 I mentioned spells out the use of low ESR caps but the MC34063 datasheet says nothing. Would any cap of proper value do?
     
  2. JohnInTX

    Moderator

    Jun 26, 2012
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    ON ti.com download it and punch in your parameters and it will give you the circuit. I didn't log in and its been awhile since I used it (it was National Semiconductor's Smart Switcher, now also owned by TI) but it used to give you a complete design with BOM, manufacturer and part numbers of the passives. Too easy.
     
  3. takao21203

    Distinguished Member

    Apr 28, 2012
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    1. You don't need a current sensing resistor. If you use one, 5%.
    2. You can use any capacitor.
    3. You may need additional filter coil if you supply a LCD.
     
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