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Low dropout 5v regulator (up to 800 mA)

Discussion in 'Electronic Design' started by John Popelish, Apr 9, 2007.

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  1. You'll also have to define "low". Normal follower output
    regulators drop about 1.5 volts, so anything lower than that
    is somebody's low drop out.
     
  2. Here is one that might suit you:
    http://focus.ti.com/lit/ds/symlink/tps79650.pdf
     
  3. Would anyone suggest a IC that is a 5V, low dropout voltage regulator
    (regulating output from a rechargeable battery pack), up to 800 mA
    current.

    thanks

    i
     
  4. LT1117
    LT1118
     
  5. On first sight, looks like just what I need!

    thanks!

    i
     
  6. Winfield

    Winfield Guest

    An attractive feature of the tps79650 family is the noise-filter
    pin in the fixed-voltage versions, which I've put to good use.

    I just wish they were also available in TO-220 style packages.
    It's rather hard to get much heat out of the surface-mounting
    packages, even with many square inches of copper. One craves
    the good old heat-sink fins.
     
  7. Winfield, something makes me confused, they say that maximum Vin is 6
    volts? (input voltage). If so, then they would not work for my 6.7v
    (actual) battery pack.
    I agree, I like TO-220 myself too.

    i
     
  8. Tam/WB2TT

    Tam/WB2TT Guest

    LM2940 (5V version)
     
  9. Yep, those are strickly low-voltage parts - I've used them
    for making 3.3V from 5V, or 1.8V from 3.3V, etc. For higher
    voltages, and for +5, etc., we use parts from the Linear
    Technology LT1084 and LT1085 family.
    That's another reason why we use the LT1084 and LT1085 parts.
     
  10. Win, right now in my DigiKey basket I have digikey item
    LM2940CT-5.0-ND. It seems to be all I want and has very low dropout at
    lower currents.

    It is described here

    http://www.national.com/pf/LM/LM2940.html

    I think that that's what I will buy, though it only goes to 1A, but
    that would be a good start for me.

    i
     
  11. I do use those, but I prefer the LT1084 and LT1085 because of
    their higher maximum current (for a better safety margin), and
    the much lower 0.75 and 0.9 C/W vs 4.0 C/W thermal resistance.
    'Course at $6.50 vs $1.35, the NSC LM2940 is somewhat cheaper.

    NSC does win the dropout-voltage contest, at 500mV vs 900mV at
    1A load. That's because they have a high-current PNP vs LTC's
    Darlington NPN pass transistor. However, LTC wins the 2.5A
    dropout-voltage contest, at 1.1 to 1.2V vs awwwkk! And, LTC
    wins the high-current saturated-output ground-current draw, at
    an attractive 0.05mA vs an ugly 130mA. Gag me with a spoon!
     
  12. A little progress report, I soldered solid copper wires to the little
    tab terminals of the battery pack, milled out the AC charger a little
    bit so that the copper wires do not obstruct inserting the battery
    pack, and ordered "chips". The wires are approximately 16 gauge, quite
    solid.

    i
     
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