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DAC53202: About the operation of DAC53202, OUT0 & OUT1

user802966
Prodigy 10 points
Part Number: DAC53202

Tool/software:

Hello.

I would like to know about the functions of the DAC53202.
I am currently experiencing a problem with a product that uses the DAC53202.
It seems that noise is being mixed into the DAC53202's I2C signal, causing it to malfunction.
The malfunction is as follows:
During DAC output, OUT0 and OUT1 sometimes unintentionally go to high impedance.
When this state occurs, both OUT0 and OUT1 remain at high impedance even if the output setting is reset.
If the DAC53202's VDD is turned off and then turned on again, it will operate normally after that.

Is there a function that performs this kind of protection in the event of unauthorized communication, etc.?
If there is such a function, how can I disable the protection after it has operated?

  • 0
    TI__Mastermind 42203 points

    Hello, 

    Can you share a schematic? Can you share a oscilloscope capture of the noisy I2C signal? 

    There is no protection from unauthorized commands. There is a high impedance power down mode for the DAC channels, but this would not be activated unless the power down command is sent. Can you write 0x1201 (if using the internal reference) or 0x0201 (if not using the internal reference) to register 0x1F to return the DACs to power up mode?

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Prodigy 10 points

    Thank you for your reply.

    I will share the circuit diagram and signal waveform.

    The I2C signal waveform was not taken when the problem occurred, but the noise condition can be confirmed.

    Also, after the problem was reproduced, 0x03F9 was written to register 0x1F, but it did not return to power-up mode. When 0x03F9 was written to register 0x1F after writing 1010 to the RESET bit of register 0x20 (COMMON-TRIGGER), it returned to power-up mode.

    Best regards.

    Circuit diagram

    Waveform1

    Waveform2

  • 0 in reply to user802966
    TI__Mastermind 42203 points

    Hello, 

    The schematic looks ok to me. Is VDD also experiencing noise? Can you measure VDD on the scope during one of the noise events that causes the outputs to go to high impedance? Perhaps the supply is dipping and causing the device to end up in an undefined state that is fixed by the power cycle or the SW reset. 

    This looks to be like a few volts of noise which causes the I2C lines to reach ~7V. This is violating the absolute maximum ratings of the part and could damage the part over time. The best solution would be to remove this noise source. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Prodigy 10 points

    Hello,

    Noise is also observed in the VDD, but not as much as in the I2C signal.
    Please refer to the waveform of CH4 (green) below.
    The symptoms improved when we adjusted the filter implemented in this part to reduce the noise.
    We tried measures such as adding a capacitor to the VDD terminal, but this had no effect.

    Therefore, we suspect that some kind of protection was activated on the IC side due to noise mixed into the I2C signal, causing it to go into POWER DOWN MODE. Therefore, I think that it is necessary to write 1010 to the RESET bit of register 0x20 (COMMON-TRIGGER) once, and then write 0x03F9 to register 0x1F in order to return to POWER UP MODE.

    Best Regards.

    CH4（GREEN）　VDD voltage

    Waveform after measures were taken

    Waveform after noise suppression

  • 0 in reply to user802966
    TI__Mastermind 42203 points

    Hello, 

    There is no noise protection in the device. The noise on VDD is violating the absolute maximum ratings of the part. It is possible that the noise on VDD is causing some latch condition in the DAC, or that the noise on I2C is registering unintended commands that are resolved with the reset command. The solution would likely be to remove the noise source.

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Prodigy 10 points

    Hello,

    The symptom was improved by adjusting the circuit constant of the noise filter on the I2C signal line.

    Thanks,