LDO with Boost Regulator. Alternatives?

Discussion in 'General Electronics Chat' started by ¡MR.AWESOME!, Sep 22, 2010.

  1. ¡MR.AWESOME!

    Thread Starter Member

    Aug 15, 2010
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    I have found this ic. I have not been able to find any other comparable devices. Are there any other ldo's with an integrated boost preregulator out there? Preferably with similar spec's. Also, is there another, simple way of incorporating a boost regulator with an ldo and having the boost regulator switch off when not needed (or an equivalent function)?

    This is for an automotive application where the circuit needs to have uninterrupted power while the vehicle is off, starting and on. The boost regulator is necessary for occasions when the vehicle is "cold cranking" and battery voltage drops down to a very low voltage.

    Thanks,
    Andrew
     
  2. tom66

    Senior Member

    May 9, 2009
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    You need to specify exactly what you need:

    • Transient input protection? For example, you mentioned when cranking you would like the regulator to operate. Spikes of voltage may be generated during this process. Spikes of voltage may also be present in normal conditions.
    • Automotive temperature range? Is it going to be in the engine compartment or another part like the passenger compartment?
    • Output voltage and current. Efficiency. Ripple voltage. And so on.
    A SEPIC converter may be able to operate during cranking, but at reduced output current.
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    Why not just use the one you found?

    It seems like a god-send. Operates from 4v lows and handles up to 72v load dump and output is seamless throughout the entire range..

    Are you having a problem getting it?
     
  4. ¡MR.AWESOME!

    Thread Starter Member

    Aug 15, 2010
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    @tom66: I am planing on handling spikes, surges reverse polarity with external components. -40C to +125C temp range is not necessary, but would be nice. It must be able to handle at least -10C to +80C. Output of 5V. Max current I will need is ~100mA. I had skipped pass SEPIC's because I heard of their terrible efficiency, but I have started to read a bit more about them and will learn a lot more so I can decide whether they are viable. Do you have any essential info about SEPIC's for me?

    @retched: I probably will use this. I was just trying to see if there were any competing products out there that may have on board reverse polarity, voltage spike and long load dump protection. Digikey is the only place I found them in stock and they are a bit expensive. Avnet has a good price, but minimum order is 50. If you found them in stock anywhere else, please let me know.

    Thanks y'all,
    Andrew
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
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  6. budo

    New Member

    Sep 23, 2010
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  7. ¡MR.AWESOME!

    Thread Starter Member

    Aug 15, 2010
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    @retched: I used the LM9076 in a previous project and it worked great for me, however, I need the regulator to supply power even when the input voltage is below the output voltage, so a normal linear regulator will not work for me.

    Both a sepic design and the aforementioned ic look like good options for me.

    I am bringing an analog signal from the vehicle onto the circuit board and am wondering about radiated emissions of the inductors in both designs. Is this something to be concerned about or not? Is one option better than the other (sepic vs maxim ic) in this regard?

    The signal may be a nice 5V rectangular waveform, a noisy -20V to +240V amplitude signal or anything in between. The signal is to be limited, filtered and run through a comparator before being used. I have a feeling the signal will give me more of a problem with the rest of the circuit than the inductors will. What do you think?
     
    Last edited: Sep 24, 2010
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Toyota didn't worry about it, why should you. ;)
     
  9. ¡MR.AWESOME!

    Thread Starter Member

    Aug 15, 2010
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    Hahaha. Oh man. Being a Chevy man, and coming from a family who buys American, I thoroughly enjoyed that. To get off topic for a bit, is that really what was causing Toyota their problems? Do you have any reading material on it for me?

    And to get back on topic, do you have any input on which one would be better? I feel that it would really all be up to inductor selection, but I may be wrong.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    No, I was just joking around... I think the jury is still out on what caused their sudden acceleration troubles.. And yesterday on NPR, I heard they initiated ANOTHER recall.

    jeesh.
     
  11. ¡MR.AWESOME!

    Thread Starter Member

    Aug 15, 2010
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    See, at least when US car makers have a problem they voluntarily issue a recall, not try to cover it up/ignore it. Because I can't resist skooling any readers of this thread, US cars don't suck and haven't for quite some time. It was for a shot time in the seventies when they sucked hardcore but they got better. Japanese carmakers saw their opportunity and pounced. They perpetuated the message that their cars were reliable and american cars weren't, and people believed cause that's all they heard Finally peeps are seeing that domestic cars are quite nice and the Toyota problems are awesome. OK im done.

    Back on topic as of ...now.
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    It didn't help that when Ford released the Focus, their advertising contained:

    "Finally Ford is AS reliable as Toyota and Honda, according to the 2006 JD Power and associates independent review!"

    That didn't help the worlds perception of American car companies.

    I drive a 1989 Olds Cutlass Ciera. Runs great. I have only put tires on it. Now it needs an O2 sensor, but that is to be expected at +140k miles.
     
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