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'[EE]: 7805 pin compatible switching regulator ?'
2001\11\13@124553 by Tobie Horswill

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Hi,

Does anyone know of a high-current drop-in replacement for a 7805/06 voltage
regulator ? My 7805 simply can't give me the required current at Vin = 24
Volts. I've heard about switching regulators but have never used them. Do
they require more external components than linear regulators ?

regards,


__________________________
Tobie Horswill
spam_OUTthorswilTakeThisOuTspamexmachina.qc.ca

Le Projet Ex Machina
Quebec, QC, CANADA

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2001\11\13@125652 by Chetan Bhargava

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7805 is available in TO3 package for high current delivery...

----- Original Message -----
From: "Tobie Horswill" <.....thorswilKILLspamspam@spam@EXMACHINA.QC.CA>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Tuesday, November 13, 2001 9:42 AM
Subject: [EE]: 7805 pin compatible switching regulator ?


> Hi,
>
> Does anyone know of a high-current drop-in replacement for a 7805/06
voltage
{Quote hidden}

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2001\11\13@131008 by David VanHorn

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At 12:42 PM 11/13/01 -0500, Tobie Horswill wrote:
>Hi,
>
>Does anyone know of a high-current drop-in replacement for a 7805/06 voltage
>regulator ? My 7805 simply can't give me the required current at Vin = 24
>Volts. I've heard about switching regulators but have never used them. Do
>they require more external components than linear regulators ?

Digikey has drop-in switcher replacements, that will run cold with 24V input.
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2001\11\13@131151 by Marcelo Yamamoto

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If I remember correctly 78xx series have a thermal shutdown. They are rated
for 1.5A. At this current and 24V supplying it, you will have:
Power= 1.5x(24-5)= 28.5W
Ensure you have a BIG heatsink or proper ventilation.
Use a linear series regulator to drop the voltage to something around 8V and
put the regulator after it. It will be more reliable than a simple
transistor and a zener in a series regulator.

Marcelo Y.

{Quote hidden}

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2001\11\13@131416 by Tobie Horswill

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Won't the TO3 version have the same problems the TO-220 version has at Vin =
24V ?

Ideally I would like to have 1AMP at Vin=24V ...


TH

{Original Message removed}

2001\11\13@132026 by David VanHorn

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At 04:10 PM 11/13/01 -0200, Marcelo Yamamoto wrote:
>If I remember correctly 78xx series have a thermal shutdown. They are rated
>for 1.5A. At this current and 24V supplying it, you will have:
>Power= 1.5x(24-5)= 28.5W
>Ensure you have a BIG heatsink or proper ventilation.
>Use a linear series regulator to drop the voltage to something around 8V and
>put the regulator after it. It will be more reliable than a simple
>transistor and a zener in a series regulator.

No matter how you slice it, it's still bologna.

If the output is 1A, then he has to get rid of 19W of heat.
Using a pre-reg just moves the heat to a different place.
This is why we use switchers. The waste will be more in the range of 0.5W.

Input power will drop from 24W to something like 5.5W.
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2001\11\13@132255 by David VanHorn

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At 01:12 PM 11/13/01 -0500, Tobie Horswill wrote:
>Won't the TO3 version have the same problems the TO-220 version has at Vin =
>24V ?
>
>Ideally I would like to have 1AMP at Vin=24V ...

It will have the same amount of heat to get rid of, but it will do a little
better at getting rid of it.
Assuming of course, a large external heatsink.

The switcher may even be less expensive than the reg and heatsink.

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2001\11\13@135116 by Bob Ammerman

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Somebody mentioned a switching reg that is pin-compatible to the 7805 at
Digikey. How can this be? Where does it get its inductor, etc (or is it some
kind of 'module')?

Any reference to a part number would be appreciated.

Thanks,

Bob Ammerman
RAm Systems

{Original Message removed}

2001\11\13@140422 by David VanHorn

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At 01:50 PM 11/13/01 -0800, Bob Ammerman wrote:
>Somebody mentioned a switching reg that is pin-compatible to the 7805 at
>Digikey. How can this be? Where does it get its inductor, etc (or is it some
>kind of 'module')?
>
>Any reference to a part number would be appreciated.

The power trends parts use a couple "turns" of track on the PCB, with an
RM-4 core clamped over them. IIRC they operate at about 1MHz.

Apparently "Power Trends" has been sucked up by TI.

http://info.digikey.com/T013/V2/337.pdf
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2001\11\13@142212 by Tobie Horswill

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OK for the switcher I don't mind changing. But what are the available
packages and external components in order to use the switching regulators ?
I would like them to be drop-in replacements ...

regards,

TH

{Original Message removed}

2001\11\13@143629 by David VanHorn

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At 01:47 PM 11/13/01 -0500, Tobie Horswill wrote:
>OK for the switcher I don't mind changing. But what are the available
>packages and external components in order to use the switching regulators ?
>I would like them to be drop-in replacements ...

It's in digikey. They offer TO-220 packages, and I think TO-3, as well as
some more complicated SIM packages.
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2001\11\13@174430 by Mirko Bakocevic

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For your problem SPS are best solution. There are many IC's that could do
job for you.
Compact solutions are always more expensive. LM 2575, 2576, 2577 could be
solution for you (check for variations). Motorola MC34060 requires more
components but is cheaper. Anyway coil is necessary.

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2001\11\13@204711 by TH

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Bob,

Here is what I've found concerning the integrated switching regulator
available from Digikey and mentionned by David VanHorn.

http://www-s.ti.com/sc/psheets/slts028b/slts028b.pdf

Really cute but expen$ive ...

regards,

TH

{Original Message removed}

2001\11\13@210207 by David VanHorn

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At 08:46 PM 11/13/01 -0500, TH wrote:
>Bob,
>
>Here is what I've found concerning the integrated switching regulator
>available from Digikey and mentionned by David VanHorn.
>
>http://www-s.ti.com/sc/psheets/slts028b/slts028b.pdf
>
>Really cute but expen$ive ...

Definitely, compared with engineering one in at the start.
National has a chip that will do half an amp, and can be fully kitted out
for under $1 in quantity.

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two or five digit supplemental codes, in an 8 pin chip, with NO external parts.

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2001\11\13@211847 by Gennette, Bruce

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Does it have to fit the pin holes on an already designed board?

If not you can use a high power series pass transistor (like a TIP2955) to
pump electrons around the regulator (the regulator still sets the voltage
output, but the current goes around it, through the transistor).

The transistor collects from the regulator's input capacitor and emits to
the output capacitor.  A low value (say 3R3), 1W resistor feeds the
transistor's base as well as the input to the regulator.  A small cap right
at the base connection helps reduce ripple by keeping the supply to the
regulator steady.

Bye.

{Original Message removed}

2001\11\13@213259 by David VanHorn

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At 01:17 PM 11/14/01 +1100, Gennette, Bruce wrote:
>Does it have to fit the pin holes on an already designed board?
>
>If not you can use a high power series pass transistor (like a TIP2955) to
>pump electrons around the regulator (the regulator still sets the voltage
>output, but the current goes around it, through the transistor).

But the heat still remains to get rid of.
If you're linear, you get 19W to get rid of, in a 24V to 5V@1A application.

Go SMPS, and it's cold.
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Got a need to read Bar codes?  http://www.barcodechip.com
Bi-directional read of UPC-A, UPC-E, EAN-8, EAN-13, JAN, and Bookland, with
two or five digit supplemental codes, in an 8 pin chip, with NO external parts.

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2001\11\14@054149 by Marcelo Yamamoto

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Regarding this issue... anyone have already tried the Starplug SMPS
controller from Philips? I have just received some samples and would like to
hear some opinions.
www.semiconductors.philips.com/powermanagement/starplug/overview/inde
x.html

Thanks,

Marcelo Y.

Mirko Bakocevic wrote:
{Quote hidden}

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