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DAC38J84: SLEEP MODE

Lolo
Prodigy 250 points

Part Number: DAC38J84
Other Parts Discussed in Thread: DAC38J82,

Hi,

I would like to power down the 2 channels DAC C and DAC D while the 2 other channels will still go on running in a full performance.

Could you tell me please which registers we have to modify ? And which power dissipation can I save ?

Best regards

Lolo

  • 0
    TI__Guru* 81485 points
    Lolo,

    you may use the DAC38j84 GUI and configure the part as DAC38j82. You will need to go through quick start and select the necessary parameters that you need. The GUI will power down the necessary analog block (DAC core sleep) and also configure the necessary JESD204B modes to power down the unused two channels.

    -Kang
  • 0 in reply to Kang Hsia
    Prodigy 250 points
    Hello,

    This answer is not good enough.
    I would like to get the details of the registers and their value to power down the 2 channels C and D while the 2 other channels still run without any degradation.

    Besides, I asked which dissipated power can I save ?

    Thanks for your support

    Lolo
  • 0 in reply to Lolo
    TI__Guru* 81485 points

    Hello Lolo,

    Let me try to explain another way as the breakdown of each individual registers for dual channel may take a couple of pages to explain.

    All the digital channels set up like interpolation filters, NCOs, mixers, and QMC logics for dual channel can be automatically set up through the DAC38j84 GUI auto-configuration setup.

    you may see the figure below I have the DAC38J82 (or any of the 82 flavor chosen as a dual channel), you can then set auto-configuration. The register needed to configure the base digital core can be listed in the lower left hand corner.

    Double click on the registers and you may dump out the necessary register settings for your system setup. You may also save the register dump as well.

    Any of the DAC3xJ82 flavor of the device will only have the channel A and B digital data path enabled (compared to 84 flavor with all four digital data path enabled)

    The analog core (DAC output), you may pick and chose whichever 2 DAC cores you want. The default will be DAC-A and DAC-B output path. However, you may configure the output mux selector/copier to output to any of the 4 DAC output core. You may even have two copies of two channels (utilizing all four DAC outputs) if you wish.

    The configuration of the dual channel digital path automatically shut-off the unused digital channels to save power. To save the power of the DAC output core, you may set the "SLEEP" function to save the DAC output core current. The current saving is the 3.3V analog supply. To use all four DAC output core, you will consume roughly 114mA on the 3.3VA. To use only two DAC output core, only roughly 64mA on the 3.3VA is used.

    To compare the power supply consumption between 4 DAC and 2 DAC mode, you may find the power consumption rating on both the DAC38J84 and DAC38J82 datasheet.

    You may see the DIGVDD (for the digital logics) and AVDD3.3V are almost halved due to the amount of data path reduction.

    Other supplies maintains relatively flat. The SERDES rail depends on the amount of SERDES lanes being used, relatively independent of the amount of the DAC.