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Does the dac7552 power down by pin allows digital communication?

Pablo Cassani
Prodigy 40 points
Other Parts Discussed in Thread: DAC7552

Hi!,

We need to have a high output voltage after power up, instead of the normal 0V on the dac7552.

One idea is to put a pull-down on the nPD pin, and pull-ups on the two outputs. The device would be in power-down mode after power-up, which would send the outputs to High-Z, and the outputs pull-ups would pull the output to the desired value.

But, after that, we need to initialize the DAC registers while the device is "powered-down", before we rise the nPD pin.

Is it going to work? Is the DAC digital section enabled and communicating while nPD is down? Is it going to keep its contents on its transition up?

Thanks

  • 0
    TI__Mastermind 46290 points

    Pablo,

    We're looking into the design database and will answer as soon as we can.

  • 0
    TI__Genius 10615 points

    Hi Pablo,

    Pablo Cassani said:

    We need to have a high output voltage after power up, instead of the normal 0V on the dac7552.

    One idea is to put a pull-down on the nPD pin, and pull-ups on the two outputs. The device would be in power-down mode after power-up, which would send the outputs to High-Z, and the outputs pull-ups would pull the output to the desired value.

    Your idea will work. I tested it in the lab and it should not cause any issues. You can power-on the part with /PD tied LOW. This will power-on the device with Hi-Z at the output.

    Pablo Cassani said:
    Is it going to work? Is the DAC digital section enabled and communicating while nPD is down? Is it going to keep its contents on its transition up?

    Yes. The power down affects only for the output stage.The digital interface will work during power down. The buffer will also keep its value when you write to it during power down.

    Let me me know if I can assist you with anything else.

  • 0 in reply to Eugenio Mejia
    Prodigy 40 points

    Thanks Eugenio!

    We will do that on our PCB and i will mark as answer as soon as we can verify it.