IS Heat Sink Required?

[Winfield Hill]

Phil Allison wrote...

"Anthony Fremont" = Congenital, Pig Ignorant Scum

That datasheet is 10-years out of date, and badly written to boot.

** My National Linear Data data book CLEARLY says 125 C for the T package.
Plus ALL the electrical specs are given with Tj in the range from 0 to 125C

NSC's more recent LM7805-series datasheets clearly specify 125C
as the maximum junction operating* temp, a limit those of us who
are familiar with using high-power ICs are more used to seeing.
If I saw a cheap commodity jelly-bean power IC with a 150C limit,
I'd certainly not take that high value seriously. And of course
I wouldn't run the junction all the way to 125C either.

* "Note 1: Operating Conditions are conditions under which the
device functions but the specifications might not be guaranteed.
For guaranteed specifications and test conditions see the
Electrical Characteristics."

 

[John Larkin]

Phil Allison wrote...

That datasheet is 10-years out of date, and badly written to boot.


NSC's more recent LM7805-series datasheets clearly specify 125C
as the maximum junction operating* temp, a limit those of us who
are familiar with using high-power ICs are more used to seeing.
If I saw a cheap commodity jelly-bean power IC with a 150C limit,
I'd certainly not take that high value seriously. And of course
I wouldn't run the junction all the way to 125C either.

* "Note 1: Operating Conditions are conditions under which the
device functions but the specifications might not be guaranteed.
For guaranteed specifications and test conditions see the
Electrical Characteristics."

I tested a bunch of power fets, just for fun. Just past 300C, they
turned on pretty hard with zero gate drive, but recovered when cooled
off. They failed hard at about 350.

John

 

[Winfield Hill]

John Larkin wrote...

I tested a bunch of power fets, just for fun. Just past 300C,
they turned on pretty hard with zero gate drive, but recovered
when cooled off. They failed hard at about 350.

I wonder if they would have turned off at 300C with reverse
gate voltage.

 

[Spehro Pefhany]

I tested a bunch of power fets, just for fun. Just past 300C, they
turned on pretty hard with zero gate drive, but recovered when cooled
off. They failed hard at about 350.

John

Power ICs with thermal shutdown seem to pick 130°C to 170°C or so,
typical, with many of the new ones having thermal hysteresis so
they'll oscillate between, say, 120°C and 170°C Tj. Sounds like the
thermal fatigue might get the part before the Tj. Maybe some have
programmable shutdown temperature, but I can't think of any offhand.


Best regards,
Spehro Pefhany

 

[Pooh Bear]

I tested a bunch of power fets, just for fun. Just past 300C, they
turned on pretty hard with zero gate drive, but recovered when cooled
off. They failed hard at about 350.

I've run TO-3 devices to about 140C case temp without drama although by then the
fabricated heatsink assembly was smelling stongly of 'hot metal', so I didn't
take it further !

I note the typical difference ( for the same die even ) in max Tj of 200C in
hermetic metal can compared to a typical 150C for plastic encapsulation. I'm aware
that metal can is a 'superior' mounting method but I'm not entirely clear where
the 'plastic' encapsulation falls down most severely. Do the mismatched thermal
coefficients of expansion create most trouble for example ?

Also it's intruiging to note the lower temp limit for power ICs typically compared
to discrete semis. I'd guess this might be because of increased leakage current
problems in an IC perhaps. Unless it's actually, say, the more complex doping of
the die itself that makes it more sensitive to temp ?

Graham

 

[Phil Allison]

"Paul Burridge"


** Drop dead - fuckhead.




......... Phil

 

[Phil Allison]

"Anthony Fremont" = Congenital, Pig Ignorant, LYING Scum
----------------------------------------------------------------------

Good for you phil,

** It is the correct OPERATING temp spec for the part.

Thermal shutdown soon intervenes if that temp is exceeded.

Something I have verified with a K type thermocouple many times.

Bet a vile, autistic PUKE like you does not even own one.

Bet a vile, autistic PUKE like you does not ever designed anything.

the datasheet I provided CLEARLY says 150C for the T
and K packages. As if any of this matters anyhow.

** But it is NOT an OPERATING temp.

All I ever wanted to
know is how you "calculated" .6W.

** Which I supplied to you in some detail earlier.

I should have given you a bullet in the head instead.

We now know that you WAG'd it, so
that answers that.

** If your "WAG'd" means using long experience and common sense to
determine the safe dissipation figure to advise the OP as opposed to some
wacky theoretical one - that is just what I did.

125C

So what,

** Proves the point - FUCKHEAD !!!

Why do you continually call me autistic?

** Because that is exactly what you are - you EVIL PUKE.

Plus a criminal, a liar and a net stalker.

Another typical Septic Tank - full of shit.

**** OFF !!!!!!!!!




......... Phil

 

[Winfield Hill]

Phil Allison wrote...

Thermal shutdown soon intervenes if that temp is exceeded.
Something I have verified with a K type thermocouple many times.

What thermal shutdown temperatures did you observe, exactly?

 

[Phil Allison]

"Spehro Pefhany"
"Phil Allison"

600mW is what I use.

** Ah - great minds .........




.......... Phil

 

[Spehro Pefhany]

** If your "WAG'd" means using long experience and common sense to
determine the safe dissipation figure to advise the OP as opposed to some
wacky theoretical one - that is just what I did.

600mW is what I use.


Best regards,
Spehro Pefhany

 

[Anthony Fremont]

"Anthony Fremont" = Congenital, Pig Ignorant, LYING Scum
--------------------------------------------------------------------- -


** It is the correct OPERATING temp spec for the part.

Thermal shutdown soon intervenes if that temp is exceeded.

Something I have verified with a K type thermocouple many times.

Now why do I find that hard to believe?

Bet a vile, autistic PUKE like you does not even own one.

Bet a vile, autistic PUKE like you does not ever designed anything.

I'd be willing to bet that you are wrong on both counts. That is
assuming that I properly translated your second rambling.

** But it is NOT an OPERATING temp.




** Which I supplied to you in some detail earlier.

I should have given you a bullet in the head instead.

Actually what you did was wave your hands wildly as if you were
calculating something only to sum it up with a personal "rule of thumb".
This, only after factoring in a set of operating conditions that you
simply fabricated in order to bolster your case.

** If your "WAG'd" means using long experience and common sense to
determine the safe dissipation figure to advise the OP as opposed to some
wacky theoretical one - that is just what I did.






** Proves the point - FUCKHEAD !!!
Hardly.



** Because that is exactly what you are - you EVIL PUKE.

Plus a criminal, a liar and a net stalker.

A criminal huh? Me thinks you are about to ensure that you need a new
ISP after making slanderous statements such as that. Care to make a
public apology instead?

 

[Phil Allison]

"Winfield Hill"

Phil Allison wrote...

What thermal shutdown temperatures did you observe, exactly?

** Win - if you supplied a context and purpose for your Q you might get a
reply.

Cos to me it looks just like another of your TROLLS.




......... Phil

 

[Phil Allison]

"Anthony Fremont" = Congenital, Pig Ignorant, LYING Scum
---------------------------------------------------------------------

Why do you continually call me autistic?

A criminal huh?

** Yes - a criminal.

Your crimes are right here for all to see on usenet.

The crime of publishing malicious libel and the crime of stalking and
harassing.

Me thinks you are about to ensure that you need a new
ISP after making slanderous statements such as that.

** You are incapable of rational thought.

Having an autistic's brain precludes that.

Plus the distinction between "libel" and "slander" has escaped you.

Care to make a public apology instead?

** You must be completely out of your head.

ROTFL.



........ Phil

 

[Pooh Bear]

"Winfield Hill"

** Win - if you supplied a context and purpose for your Q you might get a
reply.

Cos to me it looks just like another of your TROLLS.

Why do you jump to such a conclusion ?

Sounded like a practical, interesting question to me.

Graham

 

[Winfield Hill]

Phil Allison wrote...

"Winfield Hill"

** Win - if you supplied a context and purpose for your Q
you might get a reply.

Cos to me it looks just like another of your TROLLS.

You don't think I have contexts and purposes? Amazing.

 

[Winfield Hill]

Pooh Bear wrote...

Why do you jump to such a conclusion ?
Sounded like a practical, interesting question to me.

I don't think Phil Allison actually reads my posts.

 

[Pooh Bear]

Pooh Bear wrote...

I don't think Phil Allison actually reads my posts.

I find his behaviour to be highly variable.

Occasionaly he makes good sense.

Graham

 

[Phil Allison]

"Winfield Hill"

Phil Allison wrote...

You don't think I have contexts and purposes? Amazing.

** Better take some basic reading lessons - Win.

You just mangled that completely.




......... Phil

 

[Phil Allison]

"Pooh Bear" >

Why do you jump to such a conclusion ?

** Why did you jump to the conclusion that I jumped to one ?

Sounded like a practical, interesting question to me.

** Always talking about himself and not the issue.

A very narcissistic little Poopie Bear.




.......... Phil

 

[Phil Allison]

"Winfield Hill" <

I don't think Phil Allison actually reads my posts.

** I don't think Win actually reads my posts.

Just plays games by snipping and posting trolls.





......... Phil