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Thread: `NEW' Small DC-DC ATX Power Supply

  1. #91
    FLAC
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    Apr 2001
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    Originally posted by tsingsu

    If you compare e. g. the LT 1083 CP-5 with the PT6625 you see that:

    - the LT is working from 6,5 - 20 V input
    - the LT gives up to 7,5A
    - the LT has an efficiency up to 90%
    - the LT cost about 7-10$ each

    So where is the advantage of the TI PT6625 ?
    What you don't understand is that the TI part is a SWITCHING regulator and the LT 1083 is a LINEAR regulator. You can get a LM1084 5 amp regulator from national for 2 bucks. So why would you go with LT at 5 bucks? But that isn't even the point. Where did you get the notion that the LT1083 - 5 is 90% efficient with a 12 volt input? Because I am under the impression that it is more like 5/12 = 41% efficient.

    Jeff
    MPEGBOX - Plexiglass Computer
    www.mpegbox.com

  2. #92
    Maximum Bitrate eugenen's Avatar
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    Maybe were getting mixed up on part numbers here. Linear Tech has linear and switching regulators. Their linear regulators are pretty much the same as the LM1084 series. Linear regulators are not very efficient, basically divide input and output voltage to come up with the efficiency. The Linear technologies switching regulators are just the chip, yo ustill have to add the coil, and other parts. I saw these TI and they are as simple to connect as a linear regualtor, but are switching. When I started soldering up my linear regulator power supply, it grew in size and I would have to add anothe pcb to the side of my system to fit all the parts while maintaining enought space for mounting them to the heatsinks. If I use the TI ones, I get space savings because I don't need heatsinks, I will probabally get the tabbed ones and put some heatsink grease and mount them to my chassis just to be safe, but I can really simplify my design.

  3. #93
    Newbie
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    May 2002
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    Germany
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    Okay, now I got it.

    I read so many datasheets the last days that I really mixed up things between the linear and switching regulators, especially between the LT1074 and the LT1083; sorry for that.

    Anyway, space and heat are not a problem for me, but getting parts is. I can't see a chance to get these TI parts over here, so I will use some of the linear regulators - simple and cheap.

    cu
    tsingsu

  4. #94
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    great way to a flat battery if you ask me....
    C@sper - Layer-3 Project

  5. #95
    Maximum Bitrate eugenen's Avatar
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    Thats when you buy a second battery and an isolator. I plan on doing mine that way. Mine started out as just an Mp3 player, but I want to keep it on all day for other tasks so I'm dropping my linear regulators for the TI ISR's. With my low power MB, I should only pull 10-15A running, less when idle anmd waiting. The deep cycle batteries usuallt have in the three digit amp/hour rating so mince should be able to run for a while. I'm tempted to get a big solar panal and set it on the roof

  6. #96
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    did kaboom post what TI reg's he was using yet?... hope i didnt miss it... anyone know what TI are like for getting samples? if theyre anything like maxim, you could DIY this project for next to nothing
    C@sper - Layer-3 Project

  7. #97
    Maximum Bitrate eugenen's Avatar
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    Hes using the TI PT662x series. I don't know about free parts, I didn't want to wait, ordered a pair from digi-key this afternoon. I should have them friday or monday.

  8. #98
    Variable Bitrate
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    Kaboom you alive man? I am waitin to buy your PS! =)

    Grand AMplifier Project 1.0:
    http://drive.to/cliffsgrandamgt/
    http://www.astallaslions.com/carmp3/
    --------------------------------
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    -128 MB RAM
    -MPBS1 DC-DC PSU
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    -Media Engine & Windows XP
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  9. #99
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    be very careful in hooking these up... measure your car voltage dips, these regulators dont work below 9v... many cars drop below this during cranking and will mean rebooting when ya start your car..... nice parts though
    C@sper - Layer-3 Project

  10. #100
    Maximum Bitrate eugenen's Avatar
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    You must have an old battery, both mine don't even go below 11v when cranking.

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