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a short-circit tms320f28335 c2000 core

servoman aboul-ela
Prodigy 80 points
Other Parts Discussed in Thread: TMS320F28335

hi every one

i am using tms320f28335 , and i have made a shortcircuit between the supply "3.3,1.9V"and GND of MC . is that could damage the MC or its okay and MC have a protection circuit internally . plz i need help as soon as u can because i want to know if it damaged i will remove the MC from my PCB if it did not i will search for the short inside my circuit.

regards

  • 0
    TI__Expert 8500 points

    Skyman,

    Help me to understand your question a little better. You have a board where an LDO supplies the 3.3v rail and another (or maybe a second port of the first LDO) that supplies the 1.9v rail. Both of these were shorted on your board to the ground plane? If so, I would suggest the LDOs are the devices most likely affected. While there is nothing that will inherently cause damage to the device if both the 3.3v rails and the 1.9v rail are all shorted to VSS (this is essentially powering down the device), there could be some side issues affecting the device. If there is a lot of switching noise due to this short that creates alot of energy that is passed into the device you could conceivably damage the device. We do have ESD protection on the device that adheres to industry standards, however, even the best ESD circuit has its limits. In essence what I'm saying is that it is impossible for us to tell you for sure if the part was damaged or not without looking at it.

    Regards,
    Dave Foley

     

  • 0 in reply to David Foley
    Prodigy 80 points

    thank you dave for your help !

    I am a little confused , if you mean by LD0 the regulator that supply the microcontroller with 3.3v &1.9v , i am allready disconnected it "by cutting its track to MC"and i still have the short .the problem i face it is that i have a short-circuit between microcontroller pins these pins are " GPIO48,and 3.3vpin and 1.9vpin " . all my troubleshooting indicate that the short is inside the MC or between any of supply and GND pins inside the circuit , so i need to know ------ (1) if this short  could damage the microcontroller or the microcontroller can stand this short  ""i mean having internal protection againist short between supply and GND"".---- (2) what could make this short , becaues the circuit was working very good untill i turned off the power and went to take my lunch , when i came back i found this problem but before this moment it was working very good .

     

    Regards

  • 0 in reply to servoman aboul-ela
    TI__Expert 8500 points

    Skyman,

    Yes, LDO stand for Low Drop-Out regulator. I should have used the term regulator as it is not necessary to use an LDO to regulate the voltage to the chip. That is just a common way to do it.

    Q1: if this short  could damage the microcontroller or the microcontroller can stand this short  ""i mean having internal protection againist short between supply and GND"".----

    A1: If there is a short between power and ground inside of the device, then the device is damaged. There should not be a short between these pins inside of the device. If the short is outside of the device it is going to depend on what voltage reached these shorted pins. If the 3.3v regulator blew out and shorted to 1.9v, so that only 1.9v reached VDDIO and VDD then the device may be okay. If 3.3v reached the 1.9v rail (VDD) then the device is likely damaged. The 1.9v logic is only rated to 2.5v absolute maximum (Table 6.1 in the datasheet). However, like I said in my last post, an event that shorts two power rails is likely to generate some energy spikes that could damage the chip.

    Q2: what could make this short , becaues the circuit was working very good untill i turned off the power and went to take my lunch , when i came back i found this problem but before this moment it was working very good .

    A2: Typically something like this is due to some sort of electrical overstress (EOS) event. Something like a voltage or current overstress on one of the pins. You can return the device to TI or the distributor you bought it from and we can analyze it to see if there is any EOS damage, and on what pin it appears to have occurred on if you like. It is a destructive test, so we will not be able to return the part back though. But it may help you analyze what part of your circuit caused the damage.

    Regards,
    Dave Foley

     

  • 0 in reply to David Foley
    Prodigy 80 points

    thank you dave

    i found that u r right ,it has been damaged due to surge current  , and i am working to replace it  right now .

    thanks alot 

    REGARDS

  • 0 in reply to David Foley
    Prodigy 80 points

    HI DAVID

    The same problem appear again after i replace tms320f28335 with a new one . i found that the problem "short" happen during the disconnection of the tms350f28335 programmer "USB blackhawk c2000" . i am using tms320f28335 military ranking . so i need to know if it is okay to programe the tms320f28335 using this programmer , and what could make this short again . NOTE that my circuit is working very good until when i disconnect  the programmer the short appear again.

    Regards

  • 0 in reply to servoman aboul-ela
    TI__Expert 8500 points

    There are no known issues with programming the F28335 military (or non) device with the USB Blackhawk C2000 programmer. Just disconnecting a programmer should not cause EOS. When you say disconnect, do you mean physically disconnecting the JTAG header? Are you using proper ESD handling techniques, like using a wrist strap grounded through a 10K resistor? If so I cannot see why disconnecting the JTAG would cause an EOS event. When you disconnect the JTAG header, my guess is the device will start running the code that has been programmed into the device. Possibly there is something in the code that is creating an EOS condition on your board (like turning on an output buffer when an external circuit is already driving the pin). From the naked eye this would happen fast enough that it would appear to be the act of removing the JTAG which is causing the EOS event. Other than that I don't have any ideas.

    Regards,
    Dave Foley