EDAboard.com | EDAboard.de | EDAboard.co.uk | WTWH Media

yikes

Ask a question - edaboard.com

elektroda.net NewsGroups Forum Index - Electronics Design - yikes

Goto page 1, 2  Next

John Larkin
Guest

Wed May 06, 2020 7:45 pm   



We have people working at home, but some wretched soul has to come in
to work and support them. Me.

I finally got the last assembled PCB for my 3-phase alternator
simulator, the control board.

https://www.dropbox.com/s/86cl4hra89j7438/P901_Panel.jpg?raw=1

https://www.dropbox.com/s/xywr3isogqnklm7/P901_E3.jpg?raw=1

I powered up the first board and the 3.3 volt supply wouldn't come up.
It was millivolts. This drove me crazy. I checked everything five
times and finally replaced the TPS54302 chip. That didn't help, as
replacing chips tends to not help.

Finally I noticed tiny pulses on the 3.3 volt rail, so the switcher
was at least trying a little.

I connected a big bench supply to 3.3 and ramped up the current limit.
Got 0.5 amps at 0.2 volts. Hard short. The little switcher was trying
occasionally, giving up for a long time, and hardly making any
voltage.

So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

The chip appears to have molded indexes in three corners. The little
one is pin 1.

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

DJ Delorie
Guest

Wed May 06, 2020 8:45 pm   



John Larkin <jlarkin_at_highland_atwork_technology.com> writes:
Quote:
So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.


Youch!

Quote:
I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.


I had a similar problem with an LM2842. The "pin 1" indicator is a
slight difference in texture along one edge. Impossible to see if you
get anything on it. Amusingly, I was replacing it because mine also
wouldn't come up right - it was floating around 1.3v and not switching.
Turns out - and this is NOT DOCUMENTED - the switcher won't start if
anything else is powering that rail, even a tiny bit. At least they had
a drop-in replacement[*] that didn't have that problem.

[*] LMR16006YQ in case this helps anyone

boB
Guest

Wed May 06, 2020 8:45 pm   



On Wed, 06 May 2020 14:54:25 -0400, DJ Delorie <dj_at_delorie.com> wrote:

Quote:
John Larkin <jlarkin_at_highland_atwork_technology.com> writes:
So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

Youch!

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.

I had a similar problem with an LM2842. The "pin 1" indicator is a
slight difference in texture along one edge. Impossible to see if you
get anything on it. Amusingly, I was replacing it because mine also
wouldn't come up right - it was floating around 1.3v and not switching.
Turns out - and this is NOT DOCUMENTED - the switcher won't start if
anything else is powering that rail, even a tiny bit. At least they had
a drop-in replacement[*] that didn't have that problem.

[*] LMR16006YQ in case this helps anyone



Nice PCB !

John Larkin
Guest

Wed May 06, 2020 9:45 pm   



On 6 May 2020 12:55:41 -0700, Winfield Hill <winfieldhill_at_yahoo.com>
wrote:

Quote:
DJ Delorie wrote...

I had a similar problem with an LM2842. The "pin 1" indicator is a
slight difference in texture along one edge. Impossible to see if you
get anything on it. Amusingly, I was replacing it because mine also
wouldn't come up right - it was floating around 1.3v and not switching.
Turns out - and this is NOT DOCUMENTED - the switcher won't start if
anything else is powering that rail, even a tiny bit. At least they had
a drop-in replacement[*] that didn't have that problem.

[*] LMR16006YQ in case this helps anyone

Hmm, I just designed the LM2842 into my RIS-796A, where
it powers a 12V fan. Seems to work fine for that job.


My main power supply is a kilowatt of 48-volt MeanWell. The first
thing on this board is to switch that down to +12, with an ancient
LM2576-HV, and then run everything else off the +12. The regulators
get three deep.

The 2576 switches at the nosebleed rate of 52 KHz.

The first switcher I designed ran at 24 KHz, because I could hear 22K
at that time.




--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

John Larkin
Guest

Wed May 06, 2020 9:45 pm   



On Wed, 06 May 2020 12:31:03 -0700, boB <boB_at_K7IQ.com> wrote:

Quote:
On Wed, 06 May 2020 14:54:25 -0400, DJ Delorie <dj_at_delorie.com> wrote:

John Larkin <jlarkin_at_highland_atwork_technology.com> writes:
So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

Youch!

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.

I had a similar problem with an LM2842. The "pin 1" indicator is a
slight difference in texture along one edge. Impossible to see if you
get anything on it. Amusingly, I was replacing it because mine also
wouldn't come up right - it was floating around 1.3v and not switching.
Turns out - and this is NOT DOCUMENTED - the switcher won't start if
anything else is powering that rail, even a tiny bit. At least they had
a drop-in replacement[*] that didn't have that problem.

[*] LMR16006YQ in case this helps anyone



Nice PCB !





It goes in the front of this box:

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

https://www.dropbox.com/s/d5o6f8d3vb78x4f/P900_Chassis_Partial.jpg?raw=1

It's always a nail biter to bring up a big board and hope that no
fatal mistakes were made. The supplies are up now and we're jtag'ing
ARM code. The next big event will be to successfully configure the
FPGA.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

Winfield Hill
Guest

Wed May 06, 2020 9:45 pm   



DJ Delorie wrote...
Quote:

I had a similar problem with an LM2842. The "pin 1" indicator is a
slight difference in texture along one edge. Impossible to see if you
get anything on it. Amusingly, I was replacing it because mine also
wouldn't come up right - it was floating around 1.3v and not switching.
Turns out - and this is NOT DOCUMENTED - the switcher won't start if
anything else is powering that rail, even a tiny bit. At least they had
a drop-in replacement[*] that didn't have that problem.

[*] LMR16006YQ in case this helps anyone


Hmm, I just designed the LM2842 into my RIS-796A, where
it powers a 12V fan. Seems to work fine for that job.


--
Thanks,
- Win

Tim Williams
Guest

Wed May 06, 2020 10:45 pm   



"DJ Delorie" <dj_at_delorie.com> wrote in message
news:xn368cgahq.fsf_at_delorie.com...
Quote:
I had a similar problem with an LM2842. The "pin 1" indicator is a
slight difference in texture along one edge. Impossible to see if you
get anything on it. Amusingly, I was replacing it because mine also
wouldn't come up right - it was floating around 1.3v and not switching.
Turns out - and this is NOT DOCUMENTED - the switcher won't start if
anything else is powering that rail, even a tiny bit. At least they had
a drop-in replacement[*] that didn't have that problem.

[*] LMR16006YQ in case this helps anyone


Wow. TI has had some real lemons...

TPS40210 is the last one I stepped on. Has a current fault function, which
happens to be within the error amp's range for some perverse reason. That
is, the current sense range is e.g. 0-100mV nominal (proportional to error
amp output), with a fixed 150mV threshold that flips a latch and discharges
the soft start cap (basically restarting from cold, so you wait a soft-start
cycle before going it again). But the error amp doesn't saturate at a
voltage corresponding to 100mV threshold, it goes over 150mV. So it
dutifully saturates, commanding full startup current as a converter is
supposed to, and faults its retarded ass, then sits there in a fit of
hiccuping...

Fix I employed, remove the SS cap so it restarts ~immediately (within 100s
of us). This gives about half (200-300mA) the startup current compared to
nominal capacity (~500mA). Fortunately the expected load is very light, so
it should behave...

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

John Larkin
Guest

Wed May 06, 2020 10:45 pm   



On Wed, 6 May 2020 17:00:19 -0400, bitrex <user_at_example.net> wrote:

Quote:
On 5/6/2020 2:27 PM, John Larkin wrote:


We have people working at home, but some wretched soul has to come in
to work and support them. Me.

I finally got the last assembled PCB for my 3-phase alternator
simulator, the control board.

https://www.dropbox.com/s/86cl4hra89j7438/P901_Panel.jpg?raw=1

https://www.dropbox.com/s/xywr3isogqnklm7/P901_E3.jpg?raw=1

I powered up the first board and the 3.3 volt supply wouldn't come up.
It was millivolts. This drove me crazy. I checked everything five
times and finally replaced the TPS54302 chip. That didn't help, as
replacing chips tends to not help.

Finally I noticed tiny pulses on the 3.3 volt rail, so the switcher
was at least trying a little.

I connected a big bench supply to 3.3 and ramped up the current limit.
Got 0.5 amps at 0.2 volts. Hard short. The little switcher was trying
occasionally, giving up for a long time, and hardly making any
voltage.

So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

The chip appears to have molded indexes in three corners. The little
one is pin 1.

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.




Maxim "solved" that problem by making this i2c isolator
rotation-symmetrical and then they just don't put a dot indicator on the
chip.

They don't tell you that explicitly though AFAIK, they like you to
puzzle over why there isn't one and then figure out how clever they are
on your own.


Easy fix: Never Buy Maxim.

Quote:


The TPS54302 data sheet shows a square pin1 index that doesn't exist
on actual chips. Different batches are marked differently too. All are
laser markings, barely visible if the light is just right.

ICs should never have been rotationally symmetric. That was a
historical blunder.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

bitrex
Guest

Wed May 06, 2020 10:45 pm   



On 5/6/2020 2:27 PM, John Larkin wrote:
Quote:


We have people working at home, but some wretched soul has to come in
to work and support them. Me.

I finally got the last assembled PCB for my 3-phase alternator
simulator, the control board.

https://www.dropbox.com/s/86cl4hra89j7438/P901_Panel.jpg?raw=1

https://www.dropbox.com/s/xywr3isogqnklm7/P901_E3.jpg?raw=1

I powered up the first board and the 3.3 volt supply wouldn't come up.
It was millivolts. This drove me crazy. I checked everything five
times and finally replaced the TPS54302 chip. That didn't help, as
replacing chips tends to not help.

Finally I noticed tiny pulses on the 3.3 volt rail, so the switcher
was at least trying a little.

I connected a big bench supply to 3.3 and ramped up the current limit.
Got 0.5 amps at 0.2 volts. Hard short. The little switcher was trying
occasionally, giving up for a long time, and hardly making any
voltage.

So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

The chip appears to have molded indexes in three corners. The little
one is pin 1.

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.




Maxim "solved" that problem by making this i2c isolator
rotation-symmetrical and then they just don't put a dot indicator on the
chip.

They don't tell you that explicitly though AFAIK, they like you to
puzzle over why there isn't one and then figure out how clever they are
on your own.

<https://www.mouser.com/datasheet/2/256/MAX14933-938169.pdf>

bitrex
Guest

Wed May 06, 2020 11:45 pm   



On 5/6/2020 5:17 PM, John Larkin wrote:
Quote:
On Wed, 6 May 2020 17:00:19 -0400, bitrex <user_at_example.net> wrote:

On 5/6/2020 2:27 PM, John Larkin wrote:


We have people working at home, but some wretched soul has to come in
to work and support them. Me.

I finally got the last assembled PCB for my 3-phase alternator
simulator, the control board.

https://www.dropbox.com/s/86cl4hra89j7438/P901_Panel.jpg?raw=1

https://www.dropbox.com/s/xywr3isogqnklm7/P901_E3.jpg?raw=1

I powered up the first board and the 3.3 volt supply wouldn't come up.
It was millivolts. This drove me crazy. I checked everything five
times and finally replaced the TPS54302 chip. That didn't help, as
replacing chips tends to not help.

Finally I noticed tiny pulses on the 3.3 volt rail, so the switcher
was at least trying a little.

I connected a big bench supply to 3.3 and ramped up the current limit.
Got 0.5 amps at 0.2 volts. Hard short. The little switcher was trying
occasionally, giving up for a long time, and hardly making any
voltage.

So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

The chip appears to have molded indexes in three corners. The little
one is pin 1.

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.




Maxim "solved" that problem by making this i2c isolator
rotation-symmetrical and then they just don't put a dot indicator on the
chip.

They don't tell you that explicitly though AFAIK, they like you to
puzzle over why there isn't one and then figure out how clever they are
on your own.

Easy fix: Never Buy Maxim.


https://www.mouser.com/datasheet/2/256/MAX14933-938169.pdf

The TPS54302 data sheet shows a square pin1 index that doesn't exist
on actual chips. Different batches are marked differently too. All are
laser markings, barely visible if the light is just right.

ICs should never have been rotationally symmetric. That was a
historical blunder.


They could come in a few variety of shapes, like Tetris pieces. You
could really get dense-packed boards that way.

<https://www.vectorstock.com/royalty-free-vector/tetris-pieces-vector-2083884>

Hmm, maybe that's worth a patent.

DJ Delorie
Guest

Thu May 07, 2020 12:45 am   



Winfield Hill <winfieldhill_at_yahoo.com> writes:
Quote:
Hmm, I just designed the LM2842 into my RIS-796A, where
it powers a 12V fan. Seems to work fine for that job.


I used the LM2842 because I had used it successfully in other projects,
so had a working reference design to paste in. But this latest project
had two other power rails, +5 and +12, and something was leaking some of
that power into the +3.3 rail.

mpm
Guest

Thu May 07, 2020 2:45 am   



On Wednesday, May 6, 2020 at 2:27:10 PM UTC-4, John Larkin wrote:

Quote:
So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.


We had one today, too.
We use an opto to power-up a mezzanine board that draws only about 5mA @ 3.3 VDC.
We wanted to turn the board off to save power budget when it runs on battery backup. (Hardly worth the effort, but every little bit helps!)

Long story short: The EagleCAD library had the transistor side of the OPTO pin assignment reversed. Looks great on the paper schematic, not on the Gerbers!

Luckily, they make suitable opto's with the alternate pinout, so we only need to adjust the BOM and back-annotate the error.

Jasen Betts
Guest

Thu May 07, 2020 8:45 am   



On 2020-05-06, bitrex <user_at_example.net> wrote:
Quote:
On 5/6/2020 2:27 PM, John Larkin wrote:


We have people working at home, but some wretched soul has to come in
to work and support them. Me.

I finally got the last assembled PCB for my 3-phase alternator
simulator, the control board.

https://www.dropbox.com/s/86cl4hra89j7438/P901_Panel.jpg?raw=1

https://www.dropbox.com/s/xywr3isogqnklm7/P901_E3.jpg?raw=1

I powered up the first board and the 3.3 volt supply wouldn't come up.
It was millivolts. This drove me crazy. I checked everything five
times and finally replaced the TPS54302 chip. That didn't help, as
replacing chips tends to not help.

Finally I noticed tiny pulses on the 3.3 volt rail, so the switcher
was at least trying a little.

I connected a big bench supply to 3.3 and ramped up the current limit.
Got 0.5 amps at 0.2 volts. Hard short. The little switcher was trying
occasionally, giving up for a long time, and hardly making any
voltage.

So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

The chip appears to have molded indexes in three corners. The little
one is pin 1.

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.




Maxim "solved" that problem by making this i2c isolator
rotation-symmetrical and then they just don't put a dot indicator on the
chip.

They don't tell you that explicitly though AFAIK, they like you to
puzzle over why there isn't one and then figure out how clever they are
on your own.


I've seen LED matices with that feature.

https://www.alibaba.com/product-detail/super-amber-square-led-dot-matrix_60135002918.html

I got a pair of (the red version of) them in a kitset and there were no markings
for pin 1 on the board, I traced out the wiring and then noticed the symmetry.


><https://www.mouser.com/datasheet/2/256/MAX14933-938169.pdf>

looking at page 10 I'm not seeing that, the VDD pins on each side aren't
rotationally symmetrical.


--
Jasen.

bitrex
Guest

Thu May 07, 2020 9:45 am   



On 5/7/2020 3:06 AM, Jasen Betts wrote:
Quote:
On 2020-05-06, bitrex <user_at_example.net> wrote:
On 5/6/2020 2:27 PM, John Larkin wrote:


We have people working at home, but some wretched soul has to come in
to work and support them. Me.

I finally got the last assembled PCB for my 3-phase alternator
simulator, the control board.

https://www.dropbox.com/s/86cl4hra89j7438/P901_Panel.jpg?raw=1

https://www.dropbox.com/s/xywr3isogqnklm7/P901_E3.jpg?raw=1

I powered up the first board and the 3.3 volt supply wouldn't come up.
It was millivolts. This drove me crazy. I checked everything five
times and finally replaced the TPS54302 chip. That didn't help, as
replacing chips tends to not help.

Finally I noticed tiny pulses on the 3.3 volt rail, so the switcher
was at least trying a little.

I connected a big bench supply to 3.3 and ramped up the current limit.
Got 0.5 amps at 0.2 volts. Hard short. The little switcher was trying
occasionally, giving up for a long time, and hardly making any
voltage.

So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

The chip appears to have molded indexes in three corners. The little
one is pin 1.

I thought the TPS switcher might have been backwards too, since it's
basically impossible to see the pin 1 indication.




Maxim "solved" that problem by making this i2c isolator
rotation-symmetrical and then they just don't put a dot indicator on the
chip.

They don't tell you that explicitly though AFAIK, they like you to
puzzle over why there isn't one and then figure out how clever they are
on your own.


I've seen LED matices with that feature.

https://www.alibaba.com/product-detail/super-amber-square-led-dot-matrix_60135002918.html

I got a pair of (the red version of) them in a kitset and there were no markings
for pin 1 on the board, I traced out the wiring and then noticed the symmetry.


https://www.mouser.com/datasheet/2/256/MAX14933-938169.pdf

looking at page 10 I'm not seeing that, the VDD pins on each side aren't
rotationally symmetrical.



Oh you're right. I guess I mentally transposed the VDD pins with the
upper grounds.

Ok well there's still no orientation marking on the chip, I guess
they're just jerks. Should have figured Maxim wouldn't be "clever"

Mikko OH2HVJ
Guest

Thu May 07, 2020 9:45 am   



John Larkin <jlarkin_at_highland_atwork_technology.com> writes:

Quote:
So I thermal imaged it and the ARM chip was hot. It's rotated 90
degrees. I'm waiting for it to be replaced.

The chip appears to have molded indexes in three corners. The little
one is pin 1.


I've been bitten by this one, too. One is the index and two other ones
are marks from ejector pins that push out the package from the mould.
They might be in the package drawing or not, it depends.

Assembly houses I've used have never asked about this - it's probably
business as usual and noticed by pick and place camera.


--
mikko

Goto page 1, 2  Next

elektroda.net NewsGroups Forum Index - Electronics Design - yikes

Ask a question - edaboard.com

Arabic version Bulgarian version Catalan version Czech version Danish version German version Greek version English version Spanish version Finnish version French version Hindi version Croatian version Indonesian version Italian version Hebrew version Japanese version Korean version Lithuanian version Latvian version Dutch version Norwegian version Polish version Portuguese version Romanian version Russian version Slovak version Slovenian version Serbian version Swedish version Tagalog version Ukrainian version Vietnamese version Chinese version Turkish version
EDAboard.com map