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TMS320F28027: tms320f28027 dies one after another

Tobias Faschingbauer
Prodigy 160 points
Part Number: TMS320F28027

hello folks,

on my custom board i use an f28027 with 48pins which dies directly after power on. it draws around an amp and gets very hot.

i have no idea why this happens because on my previous board with the 38 pin version everything is fine.

if anyone could give me tipps why this happens it would be nice. when someone needs any schematics just say it.

one confusing thing to me is that in the corresponding launchpad schematic the test pin is connected with ground and in the datasheet it says that the test pin must be left unconnected, also the pins x1 and x2 are a bit missleading. the launchpad doesnt have them connected to anything and the datasheet says that if i dont use a crystal x1 should be tight to ground.

Greetings from Germany

  • 0
    TI__Guru 62975 points
    It sounds like you might have a short somewhere. I would recommend that you post the schematics so that others can help double-check for you.
  • 0 in reply to tlee
    Guru 30330 points

    You can also depopulate the device from your board and start checking meticulously for any shorts between you power and ground on the board.

    You are also correct about the TEST pin being grounded on the LaunchPad, but the datasheet stating that it should be unconnected. I will do some research and see if there is any negative impacts to the device operation. Similarly for X1 and X2, yes, datasheet states that they should be grounded if not used. Since the External Crystal is not populated on the board, these pins are left floating, in direct conflict of the Datasheet. You should follow the datasheet recommendations in your design. I will log the bugs and if there is an update to the F28027 LaunchPad, they will be addressed.

  • 0 in reply to tlee
    Prodigy 160 points
    Sorry but i checked the board before i soldered the uc onto the pcb and everything was fine
  • 0 in reply to Mark Labbato
    Prodigy 160 points
    I found the error by myself. I was using an eagle library in which on of the VDD and VSS pins were exchanged with each other, therefore the ic was shorted inside and soon died after this torture.
  • 0 in reply to Tobias Faschingbauer
    Guru 192875 points
    Hehe... happens. Good that you spotted this out!

    Regards,
    Gautam
  • 0 in reply to Tobias Faschingbauer
    Guru 30330 points

    That's rough, but I am glad that you were able to easily find the issue. Good luck with the next revision!