• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Subscribers 47 subscribers
  • Views 205 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DAC8771: User bit

Masayoshi Takahashi
Intellectual 1530 points
Part Number: DAC8771
Other Parts Discussed in Thread: DAC8775

Hi team,

I have some question about datasheet of DAC8771.

1. In datasheet, I found the user bit IDA, IDB and IDC as below. Could you tell me what is the use case of these bits?

2. Regarding Power-Off-Condition, the customer is separating VOUT pin and IOUT pin. In this case the customer doesn't need to care about Power-Off-Condition.

Could you tell me which should the customer set?

3. Regarding Select DAC register

Could you tell me more detail of "Channel A selected" mean? I'd like to know what is the meaning.

Regards,

Yoshi

  • 0
    TI__Intellectual 1570 points

    Hello Yoshi,

    1. The user bits IDA, IDB and IDC are general bits that can be used to for any purpose. They do not execute any specific command for the DAC8771. 

    2. For separate VOUT & IOUT ports, POC bit should be 0. This reduces the power on/ off glitch of the DAC8771.

    3. CHA needs to be enabled before writing to the DAC data or configuration registers. Without this bit, all register writes to the data or configuration registers are discarded.

    Regards,

    Reza

  • 0 in reply to Reza Abdullah
    TI__Intellectual 1530 points

    Hi Reza,

    Thanks for your answer.

    1. "ID" mean assign the identification or something to other function?

    2. I understood. Thanks for your answer.

    3. I have curious why defined "A" channel even though DAC8771 has 1 channel. Could you tell me why A channel?

    Regards,

    Yoshi

  • 0 in reply to Masayoshi Takahashi
    TI__Intellectual 1530 points

    Could you give your advice?

    Regards,

    Yoshi

  • 0 in reply to Masayoshi Takahashi
    TI__Intellectual 1530 points

    I would like to add one question about PNSEL[1:0] register.

    Does this register need to be changed according to output range?

    For instance, when the customer selecting 0-24mA output.

    Is there any difference effect when setting 01 or 11?

    Regards,

    Yoshi

  • 0 in reply to Masayoshi Takahashi
    TI__Intellectual 1570 points

    Hello Yoshi,

    1. You are right. 'ID' stands for identification. Though they have no specific purpose, one example use case would be for chip identification.

    3. The DAC8771 is the single CH version of the DAC8775 and has the exact same digital implementation. The advantage of this is that the same firmware can be used between both version of the device. The quad channel version has channels A, B, C & D where as the single channel version has only channel A.

    Regards,

    Reza

  • 0 in reply to Masayoshi Takahashi
    TI__Intellectual 1570 points

    Yoshi,

    The PNSEL bits determine which arms of the buck boost are enabled and disabled. The behavior of these bits is independent of the selected DAC range, however for proper functioning of the DAC, the power must be properly established before enabling the DAC.

    For the example you provided, PNSEL = 01 will enable the VPOS (positive arm of the buck-boost) and disable the VNEG (negative arm of the buck-boost). For the 0-24mA output, this is sufficient. If PNSEL=11, both VPOS & VNEG are enabled and this will also work for the 0-24mA range. However, the power dissipation for the second case will be slightly higher than for the first case because VNEG is enabled.

    My recommendation is to set PNSEL = 01 for unipolar current ranges. For the bipolar current range or for any VOUT range, PNSEL = 11. Please note that both VPOS & VNEG are required for all VOUT ranges, including the unipolar VOUT ranges.

    Regards,

    Reza

  • 0 in reply to Reza Abdullah
    TI__Mastermind 46290 points

    Hello Yoshi,

    Do you have any follow-up on this topic or can we consider it closed?

  • 0 in reply to Kevin Duke
    TI__Intellectual 1530 points

    Hi Kevin,

    Thanks to support from Reza, no question for now. Please close this topic.

    Regards,

    Yoshi