CPU fan buck converter, miniature

[Winfield Hill]

https://www.dropbox.com/s/wttdn9r8np3o0t6/buck_CPU-fan.JPG?dl=0

I had finished a new PCB version of my compact
250A analog pulser, with a newly-added CPU fan.
The fan was powered with an 78L12, hey, there
wasn't room for much else. But it was obvious
its 300mA would overheat the TO-92 regulator,
plus what a waste of power! I needed to fit a
buck converter. This called for a SOT-23 part;
no room for a SO-8, and SON or LFCSP packages
not allowed, too hard to solder. There are lots
of low-voltage candidates, but RIS-796A is used
up to at least 40 volts. Only one part fits the
bill: LM2842Y. And it runs at 1.25MHz, allowing
for a small inductor. The PCB circuit is only
0.4 x 0.5 inches, fits on a corner of the PCB.
(The AOZ1282CI is a close alternate 36V 450kHz.)


--
Thanks,
- Win

 

[Winfield Hill]

Winfield Hill wrote...

https://www.dropbox.com/s/wttdn9r8np3o0t6/buck_CPU-fan.JPG?dl=0

I had finished a new PCB version of my compact
250A analog pulser, with a newly-added CPU fan.
The fan was powered with an 78L12, hey, there
wasn't room for much else. But it was obvious
its 300mA would overheat the TO-92 regulator,
plus what a waste of power! I needed to fit a
buck converter. This called for a SOT-23 part;
no room for a SO-8, and SON or LFCSP packages
not allowed, too hard to solder. There are lots
of low-voltage candidates, but RIS-796A is used
up to at least 40 volts. Only one part fits the
bill: LM2842Y. And it runs at 1.25MHz, allowing
for a small inductor. The PCB circuit is only
0.4 x 0.5 inches, fits on a corner of the PCB.
(The AOZ1282CI is a close alternate 36V 450kHz.)

Here's why this is a miniature buck converter.
It's in the little green circle at the lower
right corner, of a fairly-small 3x3-inch PCB.

https://www.dropbox.com/s/iqxegp4he8d6ast/buck_in-796A.JPG?dl=0

Save yourself a copy, you might need it oneday.
I imagine it's got about 5W of capability.


--
Thanks,
- Win

 

[Phil Hobbs]

On 2020-01-26 08:44, Winfield Hill wrote:

https://www.dropbox.com/s/wttdn9r8np3o0t6/buck_CPU-fan.JPG?dl=0

I had finished a new PCB version of my compact
250A analog pulser, with a newly-added CPU fan.
The fan was powered with an 78L12, hey, there
wasn't room for much else. But it was obvious
its 300mA would overheat the TO-92 regulator,
plus what a waste of power! I needed to fit a
buck converter. This called for a SOT-23 part;
no room for a SO-8, and SON or LFCSP packages
not allowed, too hard to solder. There are lots
of low-voltage candidates, but RIS-796A is used
up to at least 40 volts. Only one part fits the
bill: LM2842Y. And it runs at 1.25MHz, allowing
for a small inductor. The PCB circuit is only
0.4 x 0.5 inches, fits on a corner of the PCB.
(The AOZ1282CI is a close alternate 36V 450kHz.)

I use a fair number of those AOZ parts--they're cheap and they just work.

There's also the AOZ1282CI-1, which gives you half the current at twice
the frequency, but is hard to get.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

On 26 Jan 2020 05:44:44 -0800, Winfield Hill <winfieldhill@yahoo.com>
wrote:

https://www.dropbox.com/s/wttdn9r8np3o0t6/buck_CPU-fan.JPG?dl=0

I had finished a new PCB version of my compact
250A analog pulser, with a newly-added CPU fan.
The fan was powered with an 78L12, hey, there
wasn't room for much else. But it was obvious
its 300mA would overheat the TO-92 regulator,
plus what a waste of power! I needed to fit a
buck converter. This called for a SOT-23 part;
no room for a SO-8, and SON or LFCSP packages
not allowed, too hard to solder. There are lots
of low-voltage candidates, but RIS-796A is used
up to at least 40 volts. Only one part fits the
bill: LM2842Y. And it runs at 1.25MHz, allowing
for a small inductor. The PCB circuit is only
0.4 x 0.5 inches, fits on a corner of the PCB.
(The AOZ1282CI is a close alternate 36V 450kHz.)

We did one box recently that has a temperature sensor on the main PCB,
which was a good idea anyhow, so now the uP can control fan speed.
That is less noisy usually, and to some extent reduces the delay
tempcos.

The uP output is PWM, lowpass filtered into an LM317. The algorithm is
a simple slow up/down counter based on temp high/low compared to the
setpoint. That's simple and stable and has no acoustic drama.

On this one, each amplifier board has its own fan, plus one for the
box. All run full blast.

https://www.dropbox.com/s/5nwlbkep2y97baq/3d_4.jpg?raw=1


On your little board, in one place two traces make a V where they hit
a pad. One of our high-PITA customers wants us to change a board
layout to eliminate any not-90-degree pad entries, mumbling something
about "acid traps", which I think may have happened a few times around
1960.





--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"

 

[Winfield Hill]

Phil Hobbs wrote...

I use a fair number of those AOZ parts--they're cheap
and they just work.

Alpha & Omega makes lots of interesting parts. And
they seem determined to sell them at very low prices.

There's also the AOZ1282CI-1, which gives you half
the current at twice the frequency, but is hard to get.

They want you to purchase full reels?
Twice the frequency, that would have put it in good
contention with the LM2842Y part. But the extra 6V
also helped in this case. Most of the 20V parts are
synchronous, save the space of a sod-123 diode.


--
Thanks,
- Win

 

[Winfield Hill]

Winfield Hill wrote...

A few years ago I starting worrying about flaring any
narrow traces as they reached a large pad, to reduce
the possibility of trace breakage or lifting. If you
start worrying about outlier cases, is there any end?

This is an example. I manually added the flaring.

https://www.dropbox.com/s/x6a82iq0nz218w2/flared-traces.JPG?dl=0


--
Thanks,
- Win

 

[Winfield Hill]

jlarkin@highlandsniptechnology.com wrote...

On your little board, in one place two traces make a
V where they hit a pad. One of our high-PITA customers
wants us to change a board layout to eliminate any
not-90-degree pad entries, mumbling something about
"acid traps", which I think may have happened a few
times around 1960.

Do you follow the principle on your layouts? Or only
for that customer? Most of the time a 90-degree rule
isn't a problem. But there are times I prefer a mecca
approach, where all traces must meet only at the pads,
despite whatever room around the pad is available.

A few years ago I starting worrying about flaring any
narrow traces as they reached a large pad, to reduce
the possibility of trace breakage or lifting. If you
start worrying about outlier cases, is there any end?


--
Thanks,
- Win

 

[Rick C]

On Sunday, January 26, 2020 at 9:16:56 PM UTC-5, Winfield Hill wrote:

jlarkin@highlandsniptechnology.com wrote...

On your little board, in one place two traces make a
V where they hit a pad. One of our high-PITA customers
wants us to change a board layout to eliminate any
not-90-degree pad entries, mumbling something about
"acid traps", which I think may have happened a few
times around 1960.

Do you follow the principle on your layouts? Or only
for that customer? Most of the time a 90-degree rule
isn't a problem. But there are times I prefer a mecca
approach, where all traces must meet only at the pads,
despite whatever room around the pad is available.

A 90 degree entry rule is not the right solution. The right rule would be to have no internal corners less than 90 degrees. I often use traces entering at a corner which the 90 degree entry rule would exclude even though it has larger than 90 degree internal corners.

I have no idea if acid traps are a real issue or not, but this is easy enough to deal within general, so I design as if it were a real issue. It would be even easier if the software had a design rule to check for that, which mine doesn't. Manual inspection is not so easy when your boards have hundreds of pads.

A few years ago I starting worrying about flaring any
narrow traces as they reached a large pad, to reduce
the possibility of trace breakage or lifting. If you
start worrying about outlier cases, is there any end?

I don't typically worry with that, but then my traces are typically not much smaller than the pad. Sometimes I have to reduce a trace width to match the pad. Pad for digital components are often 0.5 or even 0.4 mm pitch. The pad is less than 8 mils, so a 6 mil trace matches pretty well.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

On 26 Jan 2020 18:20:23 -0800, Winfield Hill <winfieldhill@yahoo.com>
wrote:

Winfield Hill wrote...

A few years ago I starting worrying about flaring any
narrow traces as they reached a large pad, to reduce
the possibility of trace breakage or lifting. If you
start worrying about outlier cases, is there any end?

This is an example. I manually added the flaring.

https://www.dropbox.com/s/x6a82iq0nz218w2/flared-traces.JPG?dl=0

PADS will do teardrops automatically, but I think they're ugly so
don't do them on my boards.

We very rarely have a board problem. We buy from known good vendors
and specify bare-board testing.

We have had some bad cheapie-quick-proto Chinese boards.



--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"

 

[Winfield Hill]

Rick C wrote...

A 90 degree entry rule is not the right solution.
The right rule would be to have no internal corners
less than 90 degrees.

I'm confused, no 45-degree direction changes in traces?


--
Thanks,
- Win

 

[Piglet]

On 27/01/2020 09:50, Winfield Hill wrote:

Rick C wrote...

A 90 degree entry rule is not the right solution.
The right rule would be to have no internal corners
less than 90 degrees.

I'm confused, no 45-degree direction changes in traces?


Perhaps they'd permit 135 degree instead

piglet

 

[Winfield Hill]

DecadentLinuxUserNumeroUno@decadence.org wrote...

I like the old, hand routed traces with nice, smooth
transitions. No corners anywhere. Even the 45s had
rounded lead ins and lead outs.

I've read that Altium has brought those back in its
last version 20. They can be automatically invoked
in tight ball-grid-array via wiring, improving the
trace clearances. Not having installed 20, I'm not
sure if they help the user employ them elsewhere.


--
Thanks,
- Win

 

Winfield Hill <winfieldhill@yahoo.com> wrote in
news:r0mbpf02cco@drn.newsguy.com:

Rick C wrote...

A 90 degree entry rule is not the right solution.
The right rule would be to have no internal corners
less than 90 degrees.

I'm confused, no 45-degree direction changes in traces?

I like the old, hand routed traces with nice, smooth transitions. No
corners anywhere. Even the 45s had rounded lead ins and lead outs.

 

Piglet <erichpwagner@hotmail.com> wrote in news:r0mdcn$pm4$1@dont-
email.me:

On 27/01/2020 09:50, Winfield Hill wrote:
Rick C wrote...

A 90 degree entry rule is not the right solution.
The right rule would be to have no internal corners
less than 90 degrees.

I'm confused, no 45-degree direction changes in traces?


Perhaps they'd permit 135 degree instead

piglet

Squiggly wiggly PCB layout pigly

 

On 27 Jan 2020 05:25:25 -0800, Winfield Hill <winfieldhill@yahoo.com>
wrote:

DecadentLinuxUserNumeroUno@decadence.org wrote...

I like the old, hand routed traces with nice, smooth
transitions. No corners anywhere. Even the 45s had
rounded lead ins and lead outs.

I've read that Altium has brought those back in its
last version 20. They can be automatically invoked
in tight ball-grid-array via wiring, improving the
trace clearances. Not having installed 20, I'm not
sure if they help the user employ them elsewhere.

PADS can do rounded corners, but it's a nuisance.

I was told to not bend the tape on tape-and-mylar boards because the
stress on the tape would allow the corners to slowly creep, and change
clearances. That, like a lot of other things, like acid traps and
right-angle reflections and a zillion bypassing rules, may have been
folklore. Layout people seldom understood electronics (still don't) so
developed a lot of lore.

BGAs with radiused bends does sound interesting.

Funny how so many ads and articles about technology are illustrated
with pics of ancient thru-hole DIP boards with rounded traces.



--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"

 

[Lasse Langwadt Christense]

mandag den 27. januar 2020 kl. 10.50.57 UTC+1 skrev Winfield Hill:

Rick C wrote...

A 90 degree entry rule is not the right solution.
The right rule would be to have no internal corners
less than 90 degrees.

I'm confused, no 45-degree direction changes in traces?

that would not make an internal corner less than 90

 

[Rick C]

On Monday, January 27, 2020 at 4:50:57 AM UTC-5, Winfield Hill wrote:

Rick C wrote...

A 90 degree entry rule is not the right solution.
The right rule would be to have no internal corners
less than 90 degrees.

I'm confused, no 45-degree direction changes in traces?

There's nothing wrong with 45 degree traces if they join the pad at the corners. The problem is not 45 degree traces. The problem is internal corners of less than 90 degrees... if there is a problem at all.

Bad?: internal corner at <90 degrees.
\ \
\ \
\ \
+-------+
| |
| PAD |
| |

OK: Internal corners >=90 degrees.
\ \
\ \
\ \
\+-------+
| |
| PAD |
| |

Is that more clear?

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Rick C]

On Monday, January 27, 2020 at 11:58:47 AM UTC-5, DecadentLinux...@decadence.org wrote:

https://www.youtube.com/watch?v=Q-_iTC5E9nU&t=1984s

Why do YouTube videos follow me around now? When I scroll the window to read comments the video stays on the screen. I can close it, but as soon as I scroll to the top and back down it returns.

Why are they making it hard to read the comments?

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

 

[John Larkin]

On Mon, 27 Jan 2020 08:12:54 -0800, jlarkin@highlandsniptechnology.com
wrote:

On 27 Jan 2020 05:25:25 -0800, Winfield Hill <winfieldhill@yahoo.com
wrote:

DecadentLinuxUserNumeroUno@decadence.org wrote...

I like the old, hand routed traces with nice, smooth
transitions. No corners anywhere. Even the 45s had
rounded lead ins and lead outs.

I've read that Altium has brought those back in its
last version 20. They can be automatically invoked
in tight ball-grid-array via wiring, improving the
trace clearances. Not having installed 20, I'm not
sure if they help the user employ them elsewhere.

PADS can do rounded corners, but it's a nuisance.

I was told to not bend the tape on tape-and-mylar boards because the
stress on the tape would allow the corners to slowly creep, and change
clearances. That, like a lot of other things, like acid traps and
right-angle reflections and a zillion bypassing rules, may have been
folklore. Layout people seldom understood electronics (still don't) so
developed a lot of lore.

BGAs with radiused bends does sound interesting.

Funny how so many ads and articles about technology are illustrated
with pics of ancient thru-hole DIP boards with rounded traces.

Exascale processing in Europe seems to use 32-pin thru-hole CPUs.

https://www.nextplatform.com/2020/01/27/european-processor-initiative-readies-prototype/


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Winfield Hill]

Winfield Hill wrote...

Winfield Hill wrote...

https://www.dropbox.com/s/wttdn9r8np3o0t6/buck_CPU-fan.JPG?dl=0

I had finished a new PCB version of my compact
250A analog pulser, with a newly-added CPU fan.
The fan was powered with an 78L12, hey, there
wasn't room for much else. But it was obvious
its 300mA would overheat the TO-92 regulator,
plus what a waste of power! I needed to fit a
buck converter. This called for a SOT-23 part;
no room for a SO-8, and SON or LFCSP packages
not allowed, too hard to solder. There are lots
of low-voltage candidates, but RIS-796A is used
up to at least 40 volts. Only one part fits the
bill: LM2842Y. And it runs at 1.25MHz, allowing
for a small inductor. The PCB circuit is only
0.4 x 0.5 inches, fits on a corner of the PCB.
(The AOZ1282CI is a close alternate 36V 450kHz.)

Here's why this is a miniature buck converter.
It's in the little green circle at the lower
right corner, of a fairly-small 3x3-inch PCB.

https://www.dropbox.com/s/iqxegp4he8d6ast/buck_in-796A.JPG?dl=0

Save yourself a copy, you might need it oneday.
I imagine it's got about 5W of capability.

Here's my smallest 100V fan supply (on the
RIS-796 non-A "digital version"). It's quite
a bit larger - high voltage dictates a larger
inductor, and an SO-8 converter package buck
converter IC. Once again, only an NSC-TI part,
the LM5163, gets the nod. Thankfully it's a
synchronous part, saving a sod-123 diode. With
0.33-ohm lo-side MOSFET, only 30mW of I2R loss,
despite a high 100V to 8 to 12V step-down ratio.

https://www.dropbox.com/s/glk4u573rnpu959/buck_CPU-fan_100V.JPG?dl=0

The 100V capability of the RIS-796 v.3 enables
pulsing 32V, 3.5A COB LEDs, which can have an
excess drop of up to 50V at 25A or higher.


--
Thanks,
- Win