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DAC712: DAC712U output voltage

Raymond He
Expert 1990 points

Part Number: DAC712

dear  

 1.   DAC712U has been used for more than 10 years in my customer device,recently, my customer purchase 240pcs DAC712U,   test 12pcs,   1pcs  DAC712 Fail

      iI is normal while DAC712u work ten minutes before, but afer ten minutes , output  voltage deviation more than %0.4

 2.   Shutdown power ,restart the device , but it is keeping output  voltage deviation more than %0.4

 3.    cross-over experiment, details data show as below

DAC712u test data

 num

test item

1# ok

2# NG

1#（change2#的NG DAC712u)

2#（change1#OK DAC712u)

1

Vcc

15.04V

15.05V

15.04V

15.05V

-14.98V

-14.98V

-14.98V

-14.98V

2

V ref

10.22V

10.17V

10.22V

10.17V

3

V in

-32088(-9.793V)

-32088(-9.793V)

-32088(-9.793V)

-32088(-9.793V)

4

V out

-9.793V

-9.839V

-9.844V

-9.789V

1#ok is qualified board and 2#NG is defective board

from test data，we can see that the output  voltage deviation phenomenon follow DAC712U   any advice？thanks in advance~

  • 0
    TI__Mastermind 18556 points

    Hi,

    0.4% error is not acceptable for DAC712U. Total unadjusted error for the device is approx. +/- 20mV ( includes INL, DNL and Gain error).

    I am curious to note the measurements for the Vref . Min and Max for reference  voltage is 9.975 to 10.025V, where as in your case you are measuring higher voltages. How are you measuring these voltages? Is this measurement done with precision multimeters?

    Please note that the LSB size of the device 305uV assuming a 10V reference and +/-10V output range.

    So for a code of -32088 should produce ideally -9.786V +/- 20mV ( Assuming offset error is nullified).

    Regards,

    AK

  • 0 in reply to Akhilesh K
    Expert 1960 points

    Direct test voltage on pin5, using Agilent 34401A precision meter measurement.

    What is the reason for the reference voltage of 10.17v and 10.22v?

    After testing the A-B-A Switching IC, we find that the problem follows the IC. Are the parameters of the new IC different from those of the old one?

    10.17V
  • 0 in reply to HY yang
    TI__Mastermind 18556 points

    Hi,

    This reference voltage looks interesting.

    Need to check with production team for any change in test program revision or limits change, Vref of 10.17 is clearly outside the limits of the specification.

    I am assuming you are using a calibrated meter. Also can you please check the reference voltage by disconnecting the trim pots from the Vref?

    I just want to isolate the reference voltage alone.

    Regards,

    AK

  • 0 in reply to Akhilesh K
    Expert 1960 points

    1. The results of VREF voltage measurement are as follows:

    DAC712
    part

    The peripheral circuit of ref is not disconnected


    VREF(V)

    Disconnect the peripheral ref circuit

    VREF（V)

    1(NG)

    10.0429

    10.0410

    2(NG)

    10.0637

    10.0617

    3(NG)

    10.0293

    10.0285

    4(OK)

    10.0083

    10.0074

    The peripheral circuit has not been changed, and there is no such problem in the past. However, the failure rate of the two batches purchased recently is as high as 30%. The failure occurs within a few hours or ten hours. What is the cause of this situation?

  • 0 in reply to HY yang
    TI__Mastermind 18556 points

    Hi,

    Is this thread taken offline and you requested for FA?

    Looking at the measurements the not good units are clearly out of specification. We can initiate an FA through the Sales team and I will be able to get help you to find out the root cause.

    Please get in touch with the concerned sales team in your area ASAP.

    Regards,

    AK

  • 0 in reply to Akhilesh K
    Expert 1960 points

    FA has been applied.

    Product return: CPR211049632

  • 0 in reply to HY yang
    TI__Mastermind 18556 points

    Hi,

    I will close this thread, as we will be interacting more on this through email.

    Regards,

    AK