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DAC7571: Some quesitons

Shu-Cheng LIN
Guru 11785 points
Part Number: DAC7571

Hi Sirs,

Sorry to bother you.

1. VDD is 5V_STBY, and I2C signal pull up to 3V3 Run, as shown in the figure, please help to confirm whether this behavior is correct? Or I2C also pull up to 3V3_STBY is more suitable?

 

2. As shown schematics, for example U7, we get DAC address as 0x98, but when the power is turned on, but it detects three addresses as 0x3E/0x6C/0x6E. By the way, we use 100KHz standard I2C, please help to confirm.

 

3. Above three addresses 0x3E/0x6C/0x6E, when we command these three addresses, only 0x6C is successfully written, but DAC output has not response.

  • 0
    TI__Genius 14220 points

    Hi Shu-Cheng,

    Thank you for your query. The VIH for this device is 0.7*VDD minimum. At 5V VDD, the minimum VIH required is 3.5V. Hence, 3.3V IO levels won't work. You need to either change the IO voltage or the VDD voltage so that the above condition is satisfied.

    The I2C address of this device is either 0x4C or 0x4D depending on the A0 pin state. 

    If you fix the IO levels, you should get a proper response from the device.

    Hope that answers your question.

    Regards,

    Uttam Sahu

    Applications Engineer, Precision DAC

  • 0 in reply to Uttam Sahu
    Guru 11785 points

    Hi Sirs,

    Thanks for your reply

    We did two experiments and the results are as follows:
    1. When we depopate two DAC ICs (U6.U7), we go to scan this bus (I2C5), we don't see the extra address (0x3E/0x6C/0x6E/0x90)
    2. When we pop the DAC IC up, we will scan the bus and see the two DAC ICs (0x4C) 0x98, (0x4D) 0x9A, but also see the extra address (0x3E/0x6C/0x6E/0x90)

    This extra address seems to be related to the DAC IC. Is it ridiculous to help confirm this part?

    After the DAC IC, the scan bus, the resulting address map is as follows:

  • 0 in reply to Shu-Cheng LIN
    Guru 11785 points

    Hi Sirs,

    Sorry for pushed, have any update on this case?

    We have follow your suggestion that to tie the VDD to 5V. So we can scan I2C address.

    We found the (0x3E/0x6C/0x6E/0x90) that don’t belong the bus.

    Thanks!!

  • 0 in reply to Shu-Cheng LIN
    Guru 11785 points

    Hi Sirs,

    Sorry for pushed, have any update on this case?

  • 0 in reply to Shu-Cheng LIN
    TI__Genius 14220 points

    Hi Shu-Cheng,

    Apologies for the delay. last week was a bit crazy for me. I can see the validity of the address 0x48 (7-bit) or 0x90 (8-bit). This is the broadcast address for DAC7571. But I don't see a reason why it should respond to the other addresses.

    You mentioned earlier that your VDD is 5V while IO levels were 3.3V. was that fixed? You need to either make the DAC VDD as 3.3V or I2C levels as 5V.

    Regards,

    Uttam

  • 0 in reply to Uttam Sahu
    TI__Genius 14220 points

    Do you have an update on this?

    Regards,

    Uttam