7805 replacement with 35 Vin

[Wouter van Ooijen]

Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
temporary solution I now use an LM317 with two resistors, but a drop-in
replacement would be nice.

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Wouter van Ooijen schrieb:
> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
> temporary solution I now use an LM317 with two resistors, but a drop-in
> replacement would be nice.
>
>  
hi Wouter,
i guess try nationals switching power supply des.
eventually reichelt.de in sande has switching supplies with four pins
and ca 3cm³ yes ³ so it cound not be sooo large.
it will supply 500ma @5V i think thy support more than 40V.
tobias
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[Brent Brown]

On 13 Oct 2009 at 10:06, Wouter van Ooijen wrote:

> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
> temporary solution I now use an LM317 with two resistors, but a drop-in
> replacement would be nice.

The ST L7805 has absolute maximum Vin of 35V. From memory I seem to think
this is slightly higher than some other brands. Close enough?

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[Wouter van Ooijen]

mail.deamon@... wrote:

> Wouter van Ooijen schrieb:
>> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
>> temporary solution I now use an LM317 with two resistors, but a drop-in
>> replacement would be nice.
>>
>>  
> hi Wouter,
> i guess try nationals switching power supply des.
> eventually reichelt.de in sande has switching supplies with four pins
> and ca 3cm³ yes ³ so it cound not be sooo large.
> it will supply 500ma @5V i think thy support more than 40V.
> tobias

not exactly a TO220 replacement, LM317 with two R's is easier. But I was
hoping for a drop-in.

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[Wouter van Ooijen]

Brent Brown wrote:
> On 13 Oct 2009 at 10:06, Wouter van Ooijen wrote:
>
>> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
>> temporary solution I now use an LM317 with two resistors, but a drop-in
>> replacement would be nice.
>
> The ST L7805 has absolute maximum Vin of 35V. From memory I seem to think
> this is slightly higher than some other brands. Close enough?

Thanx, perfect tip.


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Wouter van Ooijen

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[WH Tan]

2009/10/13 Wouter wrote:

> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
> temporary solution I now use an LM317 with two resistors, but a drop-in
> replacement would be nice.

How about this?
http://www.recom-international.com/pdf/Innoline/R-78HBxx-0.5_L.pdf


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[Peter van Hoof-2]

----- Original Message ----
> From: Wouter van Ooijen <wouter@...>
> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
> temporary solution I now use an LM317 with two resistors, but a drop-in
> replacement would be nice.


See attachment.
While not a 3 pin replacement this is a better solution than
just a few resistors with minimal components.

Peter van Hoof


     

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[Wouter van Ooijen]

Peter van Hoof wrote:

> ----- Original Message ----
>> From: Wouter van Ooijen <wouter@...>
>> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
>> temporary solution I now use an LM317 with two resistors, but a drop-in
>> replacement would be nice.
>
>
> See attachment.
> While not a 3 pin replacement this is a better solution than
> just a few resistors with minimal components.

I think you misunderstood the LM317 solution: the 317 is an adjustable
regulator with 35V Vin. The two resistors are required to set the output
to 5V.

But I already got good suggestions.


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Wouter van Ooijen

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[Olin Lathrop]

Wouter van Ooijen wrote:
> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
> temporary solution I now use an LM317 with two resistors, but a drop-in
> replacement would be nice.

At such a high voltage drop ratio, you'd normally be looking at a switching
power supply.  At 35V in 86% of the input power is wasted as heat which then
has to be gotten rid of.


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[Dwayne Reid]

At 02:06 AM 10/13/2009, Wouter van Ooijen wrote:
>Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
>temporary solution I now use an LM317 with two resistors, but a drop-in
>replacement would be nice.

How much current?

dwayne


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[Wouter van Ooijen]

> At such a high voltage drop ratio, you'd normally be looking at a switching
> power supply.  At 35V in 86% of the input power is wasted as heat which then
> has to be gotten rid of.

When 35V was the 'normal' input I would not be looking for a 35V spec'd
regulator!

In this case power is no problem (either a 24V supply or an wheelchair
accu). The current is only 30 mA anyway, so at 24V some 0.6W is dissipated.

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Wouter van Ooijen

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[M.L.-2]

On Tue, Oct 13, 2009 at 11:46 AM, Wouter van Ooijen <wouter@...> wrote:

>> At such a high voltage drop ratio, you'd normally be looking at a switching
>> power supply.  At 35V in 86% of the input power is wasted as heat which then
>> has to be gotten rid of.
>
> When 35V was the 'normal' input I would not be looking for a 35V spec'd
> regulator!
>
> In this case power is no problem (either a 24V supply or an wheelchair
> accu). The current is only 30 mA anyway, so at 24V some 0.6W is dissipated.
>
> --
>
> Wouter van Ooijen

You can also use a zener to drop a few volts from the input supply.

Vin -> zener -> small cap to ground -> 7805



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[Wouter van Ooijen]

> You can also use a zener to drop a few volts from the input supply.

A few volts? In my case the input can be as low as maybe 16V, and as
high as maybe 29V. That makes it a bit tricky to choose the zener.

But, as said, there are 7805 variants that can handle 35V, which is
exactly what I was hoping for.

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[Dwayne Reid]

At 09:46 AM 10/13/2009, Wouter van Ooijen wrote:

>The current is only 30 mA anyway, so at 24V some 0.6W is dissipated.

Do you need the accuracy of a regulator?  If not, why not consider a
zener diode and suitable resistor instead?  You could use a 1W or 2W
metal-oxide resistor and a 1W zener for about the same cost as a 7805.

You could also use a resistor and zener in front of your regulator as
a pre-regulator.  Choose the zener voltage to be above the above the
normal input voltage so that the zener is not conducting all the time
(if possible).

dwayne

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[Forrest W Christian-2]

LM2936 - 40V or LM2936HV - 60V.   I use it in applications where I have
vins from a 24VDC battery array with good success.  +60V - 50V
survivability, so you can use it for reverse polarity protection as well.

Will have to mess with input/output caps, but should be able to find a
tantalum output cap which fits your existing holes.

-forrest

Wouter van Ooijen wrote:
> Any tips for an 7805 TO220 replacement with a Vin of 35V or higher? As a
> temporary solution I now use an LM317 with two resistors, but a drop-in
> replacement would be nice.
>
>  

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