Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

  • State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 45 subscribers
  • Views 654 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DAC7728, fired, help

Yuanping XU
Prodigy 40 points
Other Parts Discussed in Thread: DAC7728, OPA2277

Hello, 

I made a board with a DAC7728, used in bipolar mode (±15V).  Vref is 2,5V, gain is set to 4x.

But some of this chips is fired  in some PCB boards. I found the fired line is  ±15V. So, I am afraid the power supply line is too thin to incur this problem.  

But the line for this chip can not larger than 11 mil, how can I solve this problem or how can I improve the layout in the new design version?

Thanks!

  • 0
    TI__Genius 10615 points

    Hi Yuanping,

    This seems like a very serious issue.

    I believe that 11 mil should be enough to deliver enough current to the DAC7728 so I don't think this would be the issue.

    To start I will need some basic information:

    • Schematic (List power supplies and voltages at pins, if not clear in the schematic)
    • Layout
    • When does the fault occur? (power-on, when writing to the device, etc)
    • What is the current limit of your power supply?
    • What is the failure percentage right now?
    • Can you send me a picture of a broken board?
    • I would also like to have a picture of the device markings.

    If you would rather discuss this information in private, is it okay to contact you through your E2E registered email?

  • 0 in reply to Eugenio Mejia
    Prodigy 40 points
    Hi Eugenio Mejia,

    Thanks for your kind response and help!

    The PACKAGE is TQFP-64. The +15V pin is 41 and 8. The -15V pin is 38 and 11. pin 54, 30, 25 are DGND and pin 9, 40 are AGND.

    This accrues when the power-on. At the beginning , small sparks will be found around pins 38 to 41 or pins 8 to 11. If I do not stop the power, smoke and fire will be found.

    The current of power supply is +15V==1A; -15V==0.5A, which gives power to one DSP28335 , eight opa2277 chips and one DAC7728.

    The failure percentage is around 50%.

    My email is ypxu@nuaa.edu.cn and I'd like send the layout and pictures through email.

    Thanks again for you help.
  • 0 in reply to Yuanping XU
    TI__Genius 10615 points
    This conversation has been taken offline.