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TLC7226: DAC IC is failing

SACHIN SHET
Prodigy 40 points
Part Number: TLC7226

Hi,

Presently using TLC 7226CN DAC IC.

I want to know in DAC chip AGND & DGND must be separate in layout? What if both are shorted.

This IC is frequently failing after 4-5 days of operation,no heating found,operated under recommended electrical rating as specified in datasheet, can I know the failure cause?

Thanks,

  • 0
    TI__Mastermind 46290 points
    Sachin,

    AGND and DGND must be electrically connected in order for the absolute maximum table conditions to be met - the two are just separated to help prevent analog and digital domains to interfere with one another in mixed signal layout.

    Can you please share your schematic? Additionally, it would be helpful to understand loading conditions etc. if that is not evident in the schematic and any other details about how the unit is being used in this 4-5 day test window.
  • 0 in reply to Kevin Duke
    TI__Mastermind 46290 points
    ...it would also be helpful to know exactly what the failure condition is.
  • 0 in reply to Kevin Duke
    Prodigy 40 points

    Thanks for reply,

    When IC is failed,observed all the 4 output channel 10V is measured.(10v is reference voltage).analog output is not changeable.

    This type of failure due to Input or Output parameters?

    DAC output connected to Op amp simple voltage follower circuit. Current measured maximum 1.2mA in between each channel.

    Input voltages

    VCC-12v

    Vref - 10v

    WR/ - 0 or 12v

    A0- 0 or 12v

    A1- 0 or 12v.

    Digital inputs - 12V.

  • 0 in reply to SACHIN SHET
    Prodigy 40 points
    If Still more information required more than this I will share schema.
  • 0 in reply to SACHIN SHET
    TI__Mastermind 46290 points
    Sachin,

    I think looking at the schematic at this point would help. Apologies for the delays, I was out of office on business travel last week.

    Is there anything else special happening during this 4-5 day window you have mentioned? How is the DAC being exercised? Just trying to understand what the possible stimulus for failure is or if the DACs are just sitting at a fixed code / load for all of this time.
  • 0 in reply to Kevin Duke
    Prodigy 40 points

    In schematic DAC out one channel connected to voltage follower,same way connected other three channel.Digital inputs from DIO 5V signal from PC.

    DAC is failing when the moment Power ON,Visible burnt mark on IC after failure. working condition in between 4-5 days absolutely working OK.

  • 0 in reply to SACHIN SHET
    TI__Mastermind 46290 points
    Sachin,

    What is happening to the system in this 4-5 day period? Is power stable and the DAC is being exercised with the digital signals? Is power being toggled repeatedly?

    The lack of any capacitance on the supply and reference lines is certainly concerning from the schematic you have shared, unless these are on another page or something.
  • 0 in reply to Kevin Duke
    TI__Mastermind 46290 points
    Sachin,

    Any update?