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Self induced PLL failure — Parallax Forums

Self induced PLL failure

BradCBradC Posts: 2,601
edited 2009-06-23 01:25 in Propeller 1
I appear to have induced a PLL failure on a propeller proto-board.

Due to a complete balls up on my part I ended up feeding somewhere between 12V and 16V at low impedance into P24.

The remainder of the propeller functions relatively normally, but it will only run on internal oscillator.

Boo Hiss!

Just a data point I guess.

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Missed it by ->" "<- that much!

Comments

  • Cluso99Cluso99 Posts: 18,071
    edited 2009-06-22 06:11
    Amazed it runs at all !!!

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-06-22 06:28
    Leave it to Cluso99 to see the bright side! smile.gif

    -Phil
  • BradCBradC Posts: 2,601
    edited 2009-06-22 08:42
    Phil Pilgrim (PhiPi) said...
    Leave it to Cluso99 to see the bright side! smile.gif

    -Phil

    Indeed. The only reason I even mentioned it was all the other reports I'd seen were purely speculative as to the cause, whereas I know for certain what made this one pop.

    It's a shame actually as I'd just converted the proto board from the on-board 5V regulator to an LM2576 to beef up the +5V rail for automotive use, but I need precise timing so I'll just have to build up another one. When I eventually get some SMD rework gear I guess I'll whip the propeller off and replace it.

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    Missed it by ->" "<- that much!
  • RaymanRayman Posts: 15,379
    edited 2009-06-22 09:07
    I've heard you can add a 80 or 100 MHz powered oscillator and use it that way... I.e., without the PLL, but still 80 MHz...

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  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-06-22 09:40
    My abused, backwards, prop forgave me. Bless

    If you are very careful then it is possible to nibble the old chip off the PCB without damage. With very fine nippers, cut the leads at the chip end just make sure that you do not twist them as that will pull the track off. A scalpel can work but the point that the lead finally gives has to be anticipated exactly or the dreaded twist will get you. Hot air can be a bit indisciminate and get all the other little bits around the chip as well, unless you put the masking gunk on them.

    Failing that a small thermo-nuclear charge ...



    As to the bright side.

    Pesimist "that glass is half empty!"

    Optimist "that glass is half full!"

    Engineer "That glass is too big!"

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  • DogPDogP Posts: 168
    edited 2009-06-22 14:29
    Ouch... that sucks. The PLLs on the props on both my proto boards failed, so I ordered replacements and swapped them (hot air to remove, then resoldered by hand). I'm glad I ordered 3 chips though, because one of those just died last week. I seem to get about 2 months of good work out of them [noparse]:([/noparse]. It's kinda annoying... every time mine have failed it's been during a reprogram. I thought it was my serial adapter that I had made using an MM232R module, so I ordered a Prop plug, but this last time was using the prop plug >_<. Mine are always running fine, I change the code and reprogram and it stops working... set RCFAST and it starts running again. I'll definitely have to look into 80MHz oscillators if this last chip dies.

    DogP
  • BradCBradC Posts: 2,601
    edited 2009-06-22 14:42
    Yes, next time I place an order I'll get some spare chips. I've used all mine pretty hard and this is the first one I've damaged (I won't say it failed as I blew its little socks off!).

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    Missed it by ->" "<- that much!
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-06-22 14:50
    At least it was blown up by work related faults. There is nothing so annoying as setting proc clock/lock options wrong and then finding that you have a perfectly good chip ignoring you (unless another programmer is made)

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  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2009-06-22 14:55
    BradC said...
    When I eventually get some SMD rework gear I guess I'll whip the propeller off and replace it.

    What version of the surface mount Prop chip did you use? If it is the QFP version you should be able to replace the chip without any surface mount rework tools. In the past I have used a sharp utility knife or dremel to cut the leads right next to the chip. You just need to be careful not to nick the PCB. Once that is gone use use a blob of solder to remove the leads and some solder wick to clean the pads. With some practice it isn't too bad!

    Robert
  • BradCBradC Posts: 2,601
    edited 2009-06-22 22:53
    Yeah, but I've been looking for a plausible excuse for SWMBO to allow me to buy a nice hot air rework station [noparse];)[/noparse]

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    Missed it by ->" "<- that much!
  • sevssevs Posts: 50
    edited 2009-06-23 01:25
    If you get really stuck (and impatient :P), i have a few DIP chips lying around you could borrow.

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