High current voltage regulator

Thanks Brian!

Reply to
sinebar
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Does anyone know of a voltage regulator that can handle 8A or more? The closest I have found is a LM338 which is rated for 5A but that isn't enough.

Reply to
Ivan

LM396K

Brian

Reply to
Brian

An interesting part, but the LM396 10A linear regulator has been discontinued. Even though it had a rather low thermal resistance, it was doomed when competing against designs using external pass- element transistors, which have better price / performance. Most discrete power transistors are rated for up to 175C junction temp, while ICs are rarely rated to be pushed that high, 125C is a more common value. Most designers don't push to these limits, but the safety margins are more friendly when using discrete parts. The LM396 has an unusual dual rating, 125C for the control circuit and 175C for the power transistor, leaving one to wonder about the IC's cross-chip temperature gradient.

--
 Thanks,
    - Win
Reply to
Winfield Hill

"Revolutionary" and discontinued ;-) ...the backside-diffusion technique was obviously a tricky thing to keep under control.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

So is there a replacement? I found LT1038 using google which looks equivelent but no source. Tried Allied and Digikey with no luck.

Reply to
sinebar

I once did a "guaranteed-to-work" back-side diffusion of two power supply rectifier diodes... what a disaster ;-)

Still looking "angry". But we had some leftover Cipro that seems to be holding it under control (actually seems to be reducing the swelling) until we can get into the doctor tomorrow. Naomi doesn't want to contend with the long wait in the ER.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Thanks again!

Reply to
sinebar

LT1581CT7 Linear Technology IC LDO REGULATOR 10A ADJ TO220-7 Voltage Adjustable

PQ7DV10 Sharp Microelectronics IC REG LDO ADJ 10A ON/OFF TO-3P Voltage Adjustable

LT1581CT7-2.5 Linear Technology IC LDO REGULATOR 10A 2.5V TO2207

All in stock at Digi-Key

Brian

Reply to
Brian

Take a look at the datasheet for an LM317. You'll see application circuits that have an external power transistor (or several of them in parallel), controlled by the LM317. (Win alluded to this in his posting.) That's probably what you'll want.

That is, if you want to use a linear regulator at all! At 8A, with a linear regulator, you will be dissipating a LOT of heat: P = ((Vin - Vout) * I), and anything more than about 10W takes a honking big heat sink to get rid of. You may want to use a switching regulator instead. But be forewarned that designing a switching regulator is not nearly as simple as designing a linear one.

Reply to
Walter Harley

Take a look at the datasheet for an LM317. You'll see application circuits that have an external power transistor (or several of them in parallel), controlled by the LM317. (Win alluded to this in his posting.) That's

probably what you'll want.

That is, if you want to use a linear regulator at all! At 8A, with a linear regulator, you will be dissipating a LOT of heat: P = ((Vin - Vout) * I), and anything more than about 10W takes a honking big heat sink to get rid of. You may want to use a switching regulator instead. But be forewarned that designing a switching regulator is not nearly as simple as designing a linear one.

I guess I should state that the regulator will drive a 4 watt CW diode laser. I plan on using a large 12 volt battery for the power supply to assure there is no ripple.

Reply to
sinebar

Hello Jim,

That sounds just like the fate of the unijunction transistor. Over-hyped in books and press but always too expensive.

I have never used any of these 'panacea chips' in designs. Somehow it doesn't feel right to sister up control circuitry and weight lifting on the same device. I guess that's why we had the 2N3055 in the olden days.

How is Naomi's hand doing?

Regards, Joerg

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Reply to
Joerg

Hello Jim,

Then I'd really not delay that trip to the doctor. I just hope it was not a brown recluse that bit her. Happens quite a lot around here and that requires immediate attention.

Regards, Joerg

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Reply to
Joerg

MAX8550A or the like should handle upto 12 Amps. Plus you don't need large capacitors . If I remember right less then 500uF .

Cheers

Reply to
lemonjuice

It's very easy to put an external pass transistor onto a standard 3 terminal regulator, look up the application notes.

Reply to
cbarn24050

** Better take care with P diss.

I hope Vin - Vout is only a few volts.

.......... Phil

Reply to
Phil Allison

Heck, I was going to suggest an ordinary 780(what was that guy's original spec?) and a mongo PNP pass transistor.

He did say, "linear", didn't he?

Thanks, Rich

Reply to
Rich Grise

"sister up"??

That has to be some kind of idiom from some other language or something, like "zaadvragende ogen" doesn't have an exact translation from Dutch to English; so, from what language is the expression that "sister up" is translated from?

Thanks, Rich

Reply to
Rich Grise, but drunk

Hello Rich,

From the guilds of the framing carpenters and the tile setters. Sistering up is what they have to do to the wood members under a floor if it won't achieve the 1/360th deflection limit for a tile floor. Even with that kind of deflection I'd still put a membrane down before laying tile.

Regards, Joerg

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Reply to
Joerg

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