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From: krw on 21 Nov 2009 13:18 On Fri, 20 Nov 2009 18:24:55 -0800 (PST), a7yvm109gf5d1(a)netzero.com wrote: >On Nov 20, 7:22 pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> OK, I just got the first board from production this morning, for this >> spectroscopy controller thing. >> >> ftp://jjlarkin.lmi.net/First.JPG >> >> It gets 12 volts in, which runs an LTM8023 switcher brick to make 3.3 >> volts. The 3.3 runs most of the logic on the board (including a >> Spartan 6 and a PLX PCIe bridge, both BGAs) and also drives four >> secondary switchers and some LDOs to make 1.2, 1.5, 1.8, 2.5, and -5 >> for various uses. >> >> So when I powered it up everything went nuts. The PLX chip was >> obviously fried. After that was pulled, the Xilinx was running hot, >> and the 3.3 volt supply was bogged down to about 2.6. The LTM >> regulator was hot. >> >> Pulled the Spartan BGA next. >> >> Now the 3.3 volt rail wants to run at 5 or so. >> >> After much head scratching, I discovered this: >> >> ftp://jjlarkin.lmi.net/Swapped.jpg >> >> The resistor that's screened "R127" is actually R129. And vice versa. >> So the switcher was programmed wrong, told to run at an absurdly low >> frequency and an absurdly high voltage. The ref designators somehow >> got misplaced during layout. We usually check for this. >> >> Apparently our production people, when semi-auto placing dense parts, >> double-check the ref designator and plop the part into the "correct" >> place, even if the machine coordinates are a little off. I'll have to >> warn them to be suspicious about cases like this, especially on first >> articles. >> >> TGIF >> >> John > >I usually produce an "assembly drawing" where another layer of text >contains the refdes inside the part outline. >This refdes text is defined at the library level and is never moved by >hand except when the component moves. >This drawing is produced separately from the silkscreen and is shipped >to the assembly house. >This is the reference, not the silkscreen. We now back-annotate the placement information into the schematic and use Crapture to generate a BOM with placement information. This is released to manufacturing via an ECO and sucked into the pick-n-place machine. The layout guy does produce an "assembly drawing" but it's only use is in inspection. When the two disagree the released BOM is "right". Only engineering can change the BOM, via another ECO) if there is a disagreement. Well, that's the process, anyway.
From: Nico Coesel on 21 Nov 2009 13:44 John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >OK, I just got the first board from production this morning, for this >spectroscopy controller thing. > >ftp://jjlarkin.lmi.net/First.JPG I assume The Brat can kiss her Christmas invitation goodbye this year :-) -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" --------------------------------------------------------------
From: Raveninghorde on 21 Nov 2009 13:59 On Fri, 20 Nov 2009 16:22:15 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >OK, I just got the first board from production this morning, for this >spectroscopy controller thing. > >ftp://jjlarkin.lmi.net/First.JPG > >It gets 12 volts in, which runs an LTM8023 switcher brick to make 3.3 >volts. The 3.3 runs most of the logic on the board (including a >Spartan 6 and a PLX PCIe bridge, both BGAs) and also drives four >secondary switchers and some LDOs to make 1.2, 1.5, 1.8, 2.5, and -5 >for various uses. > >So when I powered it up everything went nuts. The PLX chip was >obviously fried. After that was pulled, the Xilinx was running hot, >and the 3.3 volt supply was bogged down to about 2.6. The LTM >regulator was hot. > >Pulled the Spartan BGA next. > >Now the 3.3 volt rail wants to run at 5 or so. > >After much head scratching, I discovered this: > >ftp://jjlarkin.lmi.net/Swapped.jpg > >The resistor that's screened "R127" is actually R129. And vice versa. >So the switcher was programmed wrong, told to run at an absurdly low >frequency and an absurdly high voltage. The ref designators somehow >got misplaced during layout. We usually check for this. > >Apparently our production people, when semi-auto placing dense parts, >double-check the ref designator and plop the part into the "correct" >place, even if the machine coordinates are a little off. I'll have to >warn them to be suspicious about cases like this, especially on first >articles. > >TGIF > >John > > Experience has taught me to power up new boards on a bench psu by winding up the voltage from zero while monitoring the supply rails and input current.
From: Joerg on 21 Nov 2009 14:06 Raveninghorde wrote: > On Fri, 20 Nov 2009 16:22:15 -0800, John Larkin > <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >> OK, I just got the first board from production this morning, for this >> spectroscopy controller thing. >> >> ftp://jjlarkin.lmi.net/First.JPG >> >> It gets 12 volts in, which runs an LTM8023 switcher brick to make 3.3 >> volts. The 3.3 runs most of the logic on the board (including a >> Spartan 6 and a PLX PCIe bridge, both BGAs) and also drives four >> secondary switchers and some LDOs to make 1.2, 1.5, 1.8, 2.5, and -5 >> for various uses. >> >> So when I powered it up everything went nuts. The PLX chip was >> obviously fried. After that was pulled, the Xilinx was running hot, >> and the 3.3 volt supply was bogged down to about 2.6. The LTM >> regulator was hot. >> >> Pulled the Spartan BGA next. >> >> Now the 3.3 volt rail wants to run at 5 or so. >> >> After much head scratching, I discovered this: >> >> ftp://jjlarkin.lmi.net/Swapped.jpg >> >> The resistor that's screened "R127" is actually R129. And vice versa. >> So the switcher was programmed wrong, told to run at an absurdly low >> frequency and an absurdly high voltage. The ref designators somehow >> got misplaced during layout. We usually check for this. >> >> Apparently our production people, when semi-auto placing dense parts, >> double-check the ref designator and plop the part into the "correct" >> place, even if the machine coordinates are a little off. I'll have to >> warn them to be suspicious about cases like this, especially on first >> articles. >> >> TGIF >> >> John >> >> > > Experience has taught me to power up new boards on a bench psu by > winding up the voltage from zero while monitoring the supply rails and > input current. That often doesn't not help. Many switcher do nothing intil the UVLO threshold is exceeded, and then they step on it with gusto. You may not have enough time to rip out the banana plug before phssseee ... *POOF* -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: krw on 21 Nov 2009 14:35
On Sat, 21 Nov 2009 18:59:49 +0000, Raveninghorde <raveninghorde(a)invalid> wrote: >On Fri, 20 Nov 2009 16:22:15 -0800, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>OK, I just got the first board from production this morning, for this >>spectroscopy controller thing. >> >>ftp://jjlarkin.lmi.net/First.JPG >> >>It gets 12 volts in, which runs an LTM8023 switcher brick to make 3.3 >>volts. The 3.3 runs most of the logic on the board (including a >>Spartan 6 and a PLX PCIe bridge, both BGAs) and also drives four >>secondary switchers and some LDOs to make 1.2, 1.5, 1.8, 2.5, and -5 >>for various uses. >> >>So when I powered it up everything went nuts. The PLX chip was >>obviously fried. After that was pulled, the Xilinx was running hot, >>and the 3.3 volt supply was bogged down to about 2.6. The LTM >>regulator was hot. >> >>Pulled the Spartan BGA next. >> >>Now the 3.3 volt rail wants to run at 5 or so. >> >>After much head scratching, I discovered this: >> >>ftp://jjlarkin.lmi.net/Swapped.jpg >> >>The resistor that's screened "R127" is actually R129. And vice versa. >>So the switcher was programmed wrong, told to run at an absurdly low >>frequency and an absurdly high voltage. The ref designators somehow >>got misplaced during layout. We usually check for this. >> >>Apparently our production people, when semi-auto placing dense parts, >>double-check the ref designator and plop the part into the "correct" >>place, even if the machine coordinates are a little off. I'll have to >>warn them to be suspicious about cases like this, especially on first >>articles. >> >>TGIF >> >>John >> >> > >Experience has taught me to power up new boards on a bench psu by >winding up the voltage from zero while monitoring the supply rails and >input current. With switchers this rarely does anything and often makes things even worse. |