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DAC8411: Strange output waveform

Masanori Tachibana
Genius 5350 points
Part Number: DAC8411

Hello support team,

I have some questions regarding DAC8411.

Our customer is carring out the noise testing with DAC8411, and a strange phenomenon has occurred.

Operating the DAC8411 with noise superposed on the AVDD / VREF line results in an output waveform in which only MSB data is inverted due to malfunction.
Although the input digital data is straight binary, it seems that two's complementary circuits are operating as far as we see the analog output waveform.

[Normal output waveform]

[Abnormal output waveform]

We heard that it is easy to reappear by experiment as follows.
a. Apply a sine wave of 100 kHz, center voltage of 3 V, and amplitude of 2 V to AVDD / Vref.
b. Gradually lower the center voltage and set it to about 1.5 V.
c. Set the amplitude to 0 V and the center voltage to 3.3 V.

[Questions]
1. Is there a two's complement mode in DAC8411 (as a hidden mode)?
2. If there is a two's complement mode, what is the trigger to enter this mode?
3. If this mode is entered, is there any way to escape from this mode besides turning off and on the power supply?

Sincerely,
M. Tachibana

  • 0
    TI__Genius 14220 points
    Hi Tachibana,

    Thank you for your query. I am looking into your problem. I will get back by end of this week.

    Regards,
    Uttam Sahu
    Applications Engineer, Precision DACs
  • 0 in reply to Uttam Sahu
    TI__Genius 14220 points
    Hi Tachibana,

    As per my understanding there is no hidden bipolar more in DAC8411. However, I can check with the design team and confirm. Having said that, looks like the MSB is flipping somehow. Could you please answer the following questions:

    1. Are you using the EVM or you own hardware? If it's your own hardware, could you please upload the schematics?
    2. Could you please upload the scope shots of the SPI signals under working and non-working conditions?
    3. Please also upload a scope shot of the waveform seen at the power supply pin of the DAC.

    Regards,
    Uttam Sahu
    Applications Engineer, Precision DACs
  • 0 in reply to Uttam Sahu
    Genius 5350 points

    Hello Sahu-san,

    Thank you for your reply.
    This phenomenon is occurring in our customer's hardware.
    Would you please tell me your personal e-mail address?
    I'd like to send the circuit diagram to it.

    Sincerely,
    M. Tachibana

  • 0 in reply to Masanori Tachibana
    TI__Genius 14220 points
    Hi Tachibana-san,

    I have sent a friend request to you. Once you accept it, I will send my official email ID as a private message.

    Regards,
    Uttam