{DHMN-discussion} Datasheet question - ceramic board mount - DHMN discussion

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From: "j" <pert...@gmail.com>
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In-Reply-To: <CAObpcpemN49-6mo2wji+y6hSYG-Zg0n=cWCF8sXhnhuxRBq...@mail.gmail.com>
Subject: RE: {DHMN-discussion} Datasheet question - ceramic board mount
Date: Mon, 5 Nov 2012 20:11:04 -0600
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They're common anode.

 

I managed to fry a 5940 with just 1 led attached, driving it from the
arduino +5V supply - which is why I want to use the 5940 to drive a
transistor before moving forward. This is based on recommendations from TI
per this document: http://www.ti.com/lit/an/slva280/slva280.pdf Also, I
don't want to break up the LEDs into smaller groups, but rather drive
multiple transistors from each output. Ultimately, each par can with 25
lights will have its own power supply anyway. I estimate the finished
product will be 16 par cans (400 LEDs!). 

 

This one seems like it would do the job, with enough overkill that I
wouldn't have to worry about heat problems.
http://www.mouser.com/ProductDetail/Infineon-Technologies/IPP114N12N3-G/?qs=
sGAEpiMZZMvsEea7gdidXkQgIJODFu3sutGFAeM%252b%252btA%3d Is there something
else that might be a better fit for 75v .5A continuous? 

 

 

 

 

From: dhmn-discussion@googlegroups.com
[mailto:dhmn-discussion@googlegroups.com] On Behalf Of Alex Hunt
Sent: Saturday, November 03, 2012 10:56 AM
To: dhmn-discussion
Subject: Re: {DHMN-discussion} Datasheet question - ceramic board mount

 

Interesting datasheet - I can't even tell if the LEDs are common cathode or
common anode.

Things are easy with the TLC59xx chips - you have 16 channels to work with,
so break your color strings into 5 serial sets for each color.  That way the
supply voltage is manageable.  The chip has it's own driver FET and current
limit, so you don't have to worry about an external transistor.

Alex

 

On Fri, Nov 2, 2012 at 11:54 PM, j <pert...@gmail.com> wrote:

Datasheet for the LEDs says typical voltages are 2.0 for red, 3.2 for green,
and 3.1 for blue. http://www.dipmicro.com/?datasheet=HH-1000CRGBC810C-B.pdf

 

I'll have 3 transistors (one for each color) for 25 10mm LEDs using 3
separate outputs from the arduino (actually it'll be either a TLC5940 or a
TLC5923 depending on the final numbers)

 

Good point on parallel vs. series. My original thinking was that I could use
an adjustable regulator off the same 5V supply powering the arduino to get
the 2 - 3 volts I need for the LEDs. In series, the power supplies would be
50V - 75V, and beyond tolerance for the 1616. I'll continue the search
tomorrow.

 

(updated schematic attached)

 

From: dhmn-discussion@googlegroups.com
[mailto:dhmn-discussion@googlegroups.com] On Behalf Of Alex Hunt
Sent: Friday, November 02, 2012 11:11 PM


To: dhmn-discussion
Subject: Re: {DHMN-discussion} Datasheet question - ceramic board mount

 

As long as you're saturating the transistor, that one will work fine.

Don't parallel the LEDs as shown in this schematic.  The diodes would have
to be factory matched in order for that to work properly.

Assuming you have only one LED per transistor, I think you would be better
off grounding the emitter and putting the diode in series with the
collector.  That way it's a little easier to bias the transistor.

Usually the blue channel is 3V and the red & green are 2V.

Alex

 

On Fri, Nov 2, 2012 at 10:32 PM, j <pert...@gmail.com> wrote:

Ok I must be working too hard. Original calculations were correct. Just for
completeness, attachment is a rough draft of what I'm thinking. 

 

RGB LEDs draw 20ma according to the datasheet, so I estimate .5A & 1.6W @
3.2V for the red & green channels, .5A & 1W @ 2V for the red channel. I
can't find a link for the datasheet now, but most of it's in Chinese anyway.


 

This should do it?
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/KSD1616AGTA/?qs=
sGAEpiMZZMsTKkj12KWLXuW5oDYpP%252bzx4zCv16Y6MtU%3d

 

 

From: dhmn-discussion@googlegroups.com
[mailto:dhmn-discussion@googlegroups.com] On Behalf Of Alex Hunt
Sent: Friday, November 02, 2012 9:02 PM


To: dhmn-discussion
Subject: Re: {DHMN-discussion} Datasheet question - ceramic board mount

 

Do you realize that this is a surface mount part with a heatsink only 2x3mm?

Theoretically, yes.  Thermal grease, no.  This device is designed to be
soldered to the heatsink (i.e. a big chunk of copper on a PCB).  Thermal
grease can't match the thermal conductivity of copper.

How many watts do you need to dissipate?

Alex

 

On Fri, Nov 2, 2012 at 8:50 PM, j <pert...@gmail.com> wrote:

Ok, so in theory I could mount a heat sink directly to the transistor body
w/ thermal grease and achieve the same results?

 

From: dhmn-discussion@googlegroups.com
[mailto:dhmn-discussion@googlegroups.com] On Behalf Of Alex Hunt
Sent: Friday, November 02, 2012 6:53 PM
To: dhmn-discussion
Subject: Re: {DHMN-discussion} Datasheet question - ceramic board mount

 

They are talking about ceramic circuit board material.  Think of replacing
the fiberglass in a typical PCB with a ceramic substrate.  Ceramic boards
are typically used in high frequency or high temperature applications.  In
this situation a ceramic board has much higher thermal conductivity, so it
is able to remove heat from the transistor's heatsink pad more efficiently.

It is not the same as a mica wafer.  The wafer just provides an insulating
barrier - it does not improve the PCBs ability to conduct heat.

For instance:
http://www.bestpcbs.com/products/ceramic-pcb.htm

And yes - ceramic PCBs are more expensive than typical FR4.  :)

Alex

 

On Fri, Nov 2, 2012 at 5:13 PM, j <pert...@gmail.com> wrote:

While sifting through datasheets for transistors on mouser, I came across
one that showed 2 different lines for absolute maximum power dissipation.
One line for "Each terminal mounted on a recommended land" and one for
"Mounted on a ceramic board". The line for ceramic board mounting showed 4
times the max dissipation. 

 

My question then is, what exactly is ceramic mounting and is it comparable
to installing mica wafers between the transistor and the heat sink?

 

Datasheet:  http://www.mouser.com/ds/1/348/2sar533p-44342.pdf

 

 

 

 


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</o:shapelayout></xml><![endif]--></head><body lang=3DEN-US link=3Dblue =
vlink=3Dpurple><div class=3DWordSection1><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>They&#8217;re common anode.<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>I managed to fry a 5940 with just 1 led attached, driving it from the =
arduino +5V supply &#8211; which is why I want to use the 5940 to drive =
a transistor before moving forward. This is based on recommendations =
from TI per this document: </span><a =
href=3D"http://www.ti.com/lit/an/slva280/slva280.pdf">http://www.ti.com/l=
it/an/slva280/slva280.pdf</a> <span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>Also, I don&#8217;t want to break up the LEDs into smaller groups, =
but rather drive multiple transistors from each output. Ultimately, each =
par can with 25 lights will have its own power supply anyway. I estimate =
the finished product will be 16 par cans (400 LEDs!). =
</span><o:p></o:p></p><p class=3DMsoNormal><o:p>&nbsp;</o:p></p><p =
class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>This one seems like it would do the job, with enough overkill that I =
wouldn&#8217;t have to worry about heat problems. </span><a =
href=3D"http://www.mouser.com/ProductDetail/Infineon-Technologies/IPP114N=
12N3-G/?qs=3DsGAEpiMZZMvsEea7gdidXkQgIJODFu3sutGFAeM%252b%252btA%3d">http=
://www.mouser.com/ProductDetail/Infineon-Technologies/IPP114N12N3-G/?qs=3D=
sGAEpiMZZMvsEea7gdidXkQgIJODFu3sutGFAeM%252b%252btA%3d</a> <span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>Is there something else that might be a better fit for 75v .5A =
continuous? <o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><b><span =
style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span>=
</b><span style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'> =
dhmn-discussion@googlegroups.com =
[mailto:dhmn-discussion@googlegroups.com] <b>On Behalf Of </b>Alex =
Hunt<br><b>Sent:</b> Saturday, November 03, 2012 10:56 AM<br><b>To:</b> =
dhmn-discussion<br><b>Subject:</b> Re: {DHMN-discussion} Datasheet =
question - ceramic board mount<o:p></o:p></span></p><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><p class=3DMsoNormal =
style=3D'margin-bottom:12.0pt'>Interesting datasheet - I can't even tell =
if the LEDs are common cathode or common anode.<br><br>Things are easy =
with the TLC59xx chips - you have 16 channels to work with, so break =
your color strings into 5 serial sets for each color.&nbsp; That way the =
supply voltage is manageable.&nbsp; The chip has it's own driver FET and =
current limit, so you don't have to worry about an external =
transistor.<br><br>Alex<o:p></o:p></p><div><p class=3DMsoNormal =
style=3D'margin-bottom:12.0pt'><o:p>&nbsp;</o:p></p><div><p =
class=3DMsoNormal>On Fri, Nov 2, 2012 at 11:54 PM, j &lt;<a =
href=3D"mailto:pert...@gmail.com" =
target=3D"_blank">pert...@gmail.com</a>&gt; =
wrote:<o:p></o:p></p><div><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>Datasheet for the LEDs says typical voltages are 2.0 for red, 3.2 for =
green, and 3.1 for blue. </span><a =
href=3D"http://www.dipmicro.com/?datasheet=3DHH-1000CRGBC810C-B.pdf" =
target=3D"_blank">http://www.dipmicro.com/?datasheet=3DHH-1000CRGBC810C-B=
.pdf</a><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>I&#8217;ll have 3 transistors (one for each color) for 25 10mm LEDs =
using 3 separate outputs from the arduino (actually it&#8217;ll be =
either a TLC5940 or a TLC5923 depending on the final =
numbers)</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>Good point on parallel vs. series. My original thinking was that I =
could use an adjustable regulator off the same 5V supply powering the =
arduino to get the 2 &#8211; 3 volts I need for the LEDs. In series, the =
power supplies would be 50V &#8211; 75V, and beyond tolerance for the =
1616. I&#8217;ll continue the search tomorrow.</span><o:p></o:p></p><p =
class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>(updated schematic attached)</span><o:p></o:p></p><p =
class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span =
style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span>=
</b><span style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'> =
<a href=3D"mailto:dhmn-discussion@googlegroups.com" =
target=3D"_blank">dhmn-discussion@googlegroups.com</a> [mailto:<a =
href=3D"mailto:dhmn-discussion@googlegroups.com" =
target=3D"_blank">dhmn-discussion@googlegroups.com</a>] <b>On Behalf Of =
</b>Alex Hunt<br><b>Sent:</b> Friday, November 02, 2012 11:11 =
PM</span><o:p></o:p></p><div><div><p class=3DMsoNormal><br><b>To:</b> =
dhmn-discussion<br><b>Subject:</b> Re: {DHMN-discussion} Datasheet =
question - ceramic board mount<o:p></o:p></p></div></div><div><div><p =
class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>&nbsp;<o:p><=
/o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>As long as =
you're saturating the transistor, that one will work fine.<br><br>Don't =
parallel the LEDs as shown in this schematic.&nbsp; The diodes would =
have to be factory matched in order for that to work =
properly.<br><br>Assuming you have only one LED per transistor, I think =
you would be better off grounding the emitter and putting the diode in =
series with the collector.&nbsp; That way it's a little easier to bias =
the transistor.<br><br>Usually the blue channel is 3V and the red &amp; =
green are 2V.<br><br>Alex<o:p></o:p></p><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;margin-bottom:12.0pt'>&nbsp;<o:p></o:p><=
/p><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>On Fri, Nov =
2, 2012 at 10:32 PM, j &lt;<a href=3D"mailto:pert...@gmail.com" =
target=3D"_blank">pert...@gmail.com</a>&gt; =
wrote:<o:p></o:p></p><div><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>Ok I must be working too hard. Original calculations were correct. =
Just for completeness, attachment is a rough draft of what I&#8217;m =
thinking. </span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>RGB LEDs draw 20ma according to the datasheet, so I estimate .5A =
&amp; 1.6W @ 3.2V for the red &amp; green channels, .5A &amp; 1W @ 2V =
for the red channel. I can&#8217;t find a link for the datasheet now, =
but most of it&#8217;s in Chinese anyway. </span><o:p></o:p></p><p =
class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>This should do it? </span><a =
href=3D"http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/KSD16=
16AGTA/?qs=3DsGAEpiMZZMsTKkj12KWLXuW5oDYpP%252bzx4zCv16Y6MtU%3d" =
target=3D"_blank">http://www.mouser.com/ProductDetail/Fairchild-Semicondu=
ctor/KSD1616AGTA/?qs=3DsGAEpiMZZMsTKkj12KWLXuW5oDYpP%252bzx4zCv16Y6MtU%3d=
</a><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span =
style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span>=
</b><span style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'> =
<a href=3D"mailto:dhmn-discussion@googlegroups.com" =
target=3D"_blank">dhmn-discussion@googlegroups.com</a> [mailto:<a =
href=3D"mailto:dhmn-discussion@googlegroups.com" =
target=3D"_blank">dhmn-discussion@googlegroups.com</a>] <b>On Behalf Of =
</b>Alex Hunt<br><b>Sent:</b> Friday, November 02, 2012 9:02 =
PM</span><o:p></o:p></p><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><br><b>To:</=
b> dhmn-discussion<br><b>Subject:</b> Re: {DHMN-discussion} Datasheet =
question - ceramic board mount<o:p></o:p></p></div><div><p =
class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>&nbsp;<o:p><=
/o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;margin-bottom:12.0pt'>Do you realize =
that this is a surface mount part with a heatsink only =
2x3mm?<br><br>Theoretically, yes.&nbsp; Thermal grease, no.&nbsp; This =
device is designed to be soldered to the heatsink (i.e. a big chunk of =
copper on a PCB).&nbsp; Thermal grease can't match the thermal =
conductivity of copper.<br><br>How many watts do you need to =
dissipate?<br><br>Alex<o:p></o:p></p><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;margin-bottom:12.0pt'>&nbsp;<o:p></o:p><=
/p><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>On Fri, Nov =
2, 2012 at 8:50 PM, j &lt;<a href=3D"mailto:pert...@gmail.com" =
target=3D"_blank">pert...@gmail.com</a>&gt; =
wrote:<o:p></o:p></p><div><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>Ok, so in theory I could mount a heat sink directly to the transistor =
body w/ thermal grease and achieve the same =
results?</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span =
style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span>=
</b><span style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'> =
<a href=3D"mailto:dhmn-discussion@googlegroups.com" =
target=3D"_blank">dhmn-discussion@googlegroups.com</a> [mailto:<a =
href=3D"mailto:dhmn-discussion@googlegroups.com" =
target=3D"_blank">dhmn-discussion@googlegroups.com</a>] <b>On Behalf Of =
</b>Alex Hunt<br><b>Sent:</b> Friday, November 02, 2012 6:53 =
PM<br><b>To:</b> dhmn-discussion<br><b>Subject:</b> Re: =
{DHMN-discussion} Datasheet question - ceramic board =
mount</span><o:p></o:p></p><div><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>&nbsp;<o:p><=
/o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;margin-bottom:12.0pt'>They are talking =
about ceramic circuit board material.&nbsp; Think of replacing the =
fiberglass in a typical PCB with a ceramic substrate.&nbsp; Ceramic =
boards are typically used in high frequency or high temperature =
applications.&nbsp; In this situation a ceramic board has much higher =
thermal conductivity, so it is able to remove heat from the transistor's =
heatsink pad more efficiently.<br><br>It is not the same as a mica =
wafer.&nbsp; The wafer just provides an insulating barrier - it does not =
improve the PCBs ability to conduct heat.<br><br>For instance:<br><a =
href=3D"http://www.bestpcbs.com/products/ceramic-pcb.htm" =
target=3D"_blank">http://www.bestpcbs.com/products/ceramic-pcb.htm</a><br=
><br>And yes - ceramic PCBs are more expensive than typical FR4.&nbsp; =
:)<br><br>Alex<o:p></o:p></p><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;margin-bottom:12.0pt'>&nbsp;<o:p></o:p><=
/p><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>On Fri, Nov =
2, 2012 at 5:13 PM, j &lt;<a href=3D"mailto:pert...@gmail.com" =
target=3D"_blank">pert...@gmail.com</a>&gt; =
wrote:<o:p></o:p></p><div><div><blockquote =
style=3D'border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in =
6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0in;margin-bottom:5=
.0pt'><div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>While sifting through datasheets for transistors on mouser, I came =
across one that showed 2 different lines for absolute maximum power =
dissipation. One line for &#8220;Each terminal mounted on a recommended =
land&#8221; and one for&nbsp; &#8220;Mounted on a ceramic board&#8221;. =
The line for ceramic board mounting showed 4 times the max dissipation. =
</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>My question then is, what exactly is ceramic mounting and is it =
comparable to installing mica wafers between the transistor and the heat =
sink?</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>&nbsp;</span><o:p></o:p></p><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497=
D'>Datasheet: &nbsp;</span><a =
href=3D"http://www.mouser.com/ds/1/348/2sar533p-44342.pdf" =
target=3D"_blank">http://www.mouser.com/ds/1/348/2sar533p-44342.pdf</a><o=
:p></o:p></p></div></blockquote></div></div></div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>&nbsp;<o:p><=
/o:p></p></div></div></div></div></div></div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>&nbsp;<o:p><=
/o:p></p></div></div></div></div></div><p class=3DMsoNormal =
style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>&nbsp;<o:p><=
/o:p></p></div></div></div></div></div></div><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p></div></div></body></html>
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