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 Previous  1, 2

Chris Jones
Guest

Thu May 07, 2020 2:45 pm   



On 07/05/2020 23:06, Arie de Muynck wrote:
Quote:
On 2020-05-06 23:00, bitrex 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.

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


Lots of small signal dual MOSFETs are like that, e.g.:
   https://www.diodes.com/assets/Datasheets/ds30204.pdf

I put a lot of N-channel and P-channel like that in several designs. I
had to explain more than three times to production that there was no pin
1 marking because it worked the same when reversed.


The time consumed in such conversations can make it quite costly.

Arie de Muynck
Guest

Thu May 07, 2020 2:45 pm   



On 2020-05-06 23:00, bitrex 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.

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


Lots of small signal dual MOSFETs are like that, e.g.:
https://www.diodes.com/assets/Datasheets/ds30204.pdf

I put a lot of N-channel and P-channel like that in several designs. I
had to explain more than three times to production that there was no pin
1 marking because it worked the same when reversed.


Guest

Thu May 07, 2020 4:45 pm   



On Thu, 07 May 2020 11:06:28 +0300, Mikko OH2HVJ
<mikko.syrjalahti_at_nospam.fi> 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.

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.


These chips are picked from a tray and in that case the Universal
machine assumes that they are oriented correctly. The operator put
them in wrong.

I've alerted QC to give particular attention to these ST chips in the
future, and our P+P operator is sufficiently embarassed.

The FLIR thermal imager was worth the absurd price we paid for it. It
answers the often vexing question "where is the current going?"



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

Arie de Muynck
Guest

Thu May 07, 2020 4:45 pm   



On 2020-05-07 15:31, Chris Jones wrote:
Quote:
On 07/05/2020 23:06, Arie de Muynck wrote:

Lots of small signal dual MOSFETs are like that, e.g.:
    https://www.diodes.com/assets/Datasheets/ds30204.pdf

I put a lot of N-channel and P-channel like that in several designs. I
had to explain more than three times to production that there was no
pin 1 marking because it worked the same when reversed.


The time consumed in such conversations can make it quite costly.


Not in 10K+ runs. The time (= cost) on the pick and place machine for 1
instead of 2 components already made up for that. I just got a call once
when a new design was entered into the machine.

Also, it saves enormously in set up cost to minimize in different
components, so use the same value as often as possible. Example:
resistor networks, we used 100K's of 4 single resistors in a 0804
package. The buying cost per package is way below the pick and place
cost for a package so it is a lot cheaper than using separate resistors.
I just designed with 'mostly' 10K (logic, pull-up) and 50R (DDR
terminators). Example:
<https://www.digikey.com/product-detail/en/bourns-inc/CAY10-103J4LF/CAY10-103J4LFTR-ND/3593174>

Goto page Previous  1, 2

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