Recommendation for 5A regulator IC - 7.4V to 6.0V

Discussion in 'The Projects Forum' started by dumpystig, Jan 2, 2014.

  1. dumpystig

    Thread Starter New Member

    Apr 10, 2013
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    I'm installing a LiPo pack in a 1/8 RC buggy receiver. The LiPo is 7.4V 2100mAH, the receiver and servos require a good regulated 6V.
    I've looked at generic SBEC units but most are of Chinese origin and are pretty crap, they do not output anywhere near 5A, have way too much ripple and do not neccessarily provide the required constant 6V.

    I have googled but not found a suitable regulator for the circuit I want to build. The aim is to make it as small as possible with the minimum of components, supplying a highly regulated constant 6V at a maximum 5A.

    Any pointers to a suitable regulator IC would be appreciated.
     
    Last edited: Jan 2, 2014
  2. #12

    Expert

    Nov 30, 2010
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    This reminds me of the sign in the print shop that says, Fast, Good, and Cheap...pick any two.

    You want Small, High Current, and Low Dropout. I think this is going to end up as, "Pick any two".
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    Are you sure the receiver and servos need 5A?
     
  4. dumpystig

    Thread Starter New Member

    Apr 10, 2013
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    OK, if I have to go for 2-out-of-3 let's make it small and low dropout...

    And after a little more research I think 3A may be just OK for the job.
     
  5. #12

    Expert

    Nov 30, 2010
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    Here's one, but be careful not to go over 7.5 volts input. Very tight limit there.
     
  6. wayneh

    Expert

    Sep 9, 2010
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    I might be missing something (like how much precision is required), but I'd consider 2 beefy diodes in series. This would drop ~1.3V or a bit more if the load is really 5A.
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Fully charged 2-cell LiPO is actually at 8.4 volts (4.2 per cell). Nominal is 3.7 volts per cell (7.4 volts per pack) and do not go below 3 volts per cell (6.0 volts) for durability.
     
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  8. dumpystig

    Thread Starter New Member

    Apr 10, 2013
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    Thanks for the link #12, I'm looking into that now.

    wayneh - the RX unit needs exactly 6V. The servo specs give Torque and Speed values at both 4.8V and 6V, so the closer to, but not more than 6V would be the ideal.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    There are a lot of pre-built DC-DC converters on e-bay that might meet your needs. If you could use 5V, you'd find more choices.
     
  10. #12

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    I think Gopher just shot this chip in the head.
     
  11. dumpystig

    Thread Starter New Member

    Apr 10, 2013
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    Yeah #12 unfortunately that's your suggestion ruled out.

    Thanks for pointing that out GopherT - I already knew that but in my eagerness completely failed to give it any thought :(

    I already have several Buck Converters from ebay but I want to have the output as close to 6V as possible, and they are also a bit large for the space I have available.
     
  12. wayneh

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    Sep 9, 2010
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    Uh oh. So now we need 6.0±0.1(?) V at 5A, and a small but unstated package size? Getting tougher.
     
  13. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Regulate only what needs regulation, like the RX. The servos likely dont care...
     
  14. crutschow

    Expert

    Mar 14, 2008
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    How about an LT3083? It's a 3A, low-dropout (310mV), 23V maximum input regulator. An added feature (not needed here) is that the output can be adjusted down to 0V.
     
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  15. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Which means at battery low end, the linear regulator has zero dropout voltage.

    He could build a good, ultra low dropout 6V regulator to put out as much current as desired using the LP2975 controller and external FET. I know of know IC reg that cn approach the same.

    http://www.ti.com/product/lp2975
     
  16. crutschow

    Expert

    Mar 14, 2008
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    The LT3083 has a 310mV dropout voltage so the end of life voltage for the battery would be 6.31V which, I think, would extract most of the available battery energy.
     
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