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Current Output Model of DAC3482

David Liu2
Prodigy 40 points
Other Parts Discussed in Thread: DAC3482, TRF3705

Hi,

We choose DAC3482 using on our new project, and try to build a 5th order LPF in current output. But we found the port type of current output in IBIS model is input port as we import to Mentor's tool, HyperLynx. Could you provide me the correct model? Or could you tell me how to model the current output?

Thanks

David

  • 0
    TI__Guru* 78634 points

    David,

    To model the analog output, we typically use SPICE simulators such as TI TINA simulator.

    http://www.ti.com/tool/tina-ti 

    Since the DAC348x has current steering output architecture. You can model the DAC's output as current sources. The current sources consist of both DC and AC components to provide biasing and ac swing.

    The attached zip file has a powerpoint presentation and two TINA files. The powerpoint provides a brief tutorial on the modeling of the DAC output. You may also refer to the TINA files for the simulation. If you want your model to be more accurate, you can add the IBIS model package parasitic info to the TINA simulator. See the file "DAC348x_TRF3705_with_package_parasitic.TSC" for more detail. 

    FYI, the DAC348x IBIS model can also be found on the TI web under DAC348x product folder page. 

    -KH

    DAC3484 Output Model.zip
  • 0 in reply to Kang Hsia
    Prodigy 40 points

    Hi Kdang,

    Thanks a lot. Yes, it is useful to me.

    But I still have some question about the DC specification of DAC output in datasheet, see the below pic.

    1. Why you don't add the output resistance (300 kohm) and capacitance (5pF) in your model?

    2. In your model the AC source is a 1A amplitude 100MHz sine wave. In real operation, what is the max. and min. range of output current?

    Can I control the value of output current?

     

    Thanks and Best Regards,

    David

  • 0 in reply to David Liu2
    TI__Guru* 78634 points

    David,

    1. Yes, you can add these two values as well. These are designer's conservative estimate and can be added before the package parasitic. 

    2. The output current is not 1A. The actual DAC output is modeled with voltage controlled current sources. 1V of voltage supply means 10mA of AC current. There is also a constant 10mA DC current sourcing from the DAC. Both the AC and DC components forms the 20mAFS current. The amplitude of the AC current can be controlled by the voltage source. 

    -KH

    DAC348x_TRF3705_with_package_parasitic - autosave 12-07-05 13_28.TSC
  • 0 in reply to Kang Hsia
    Intellectual 325 points

    Hi Kang,

    Thanks very much for your kindly support. It is very clear to understand for me, I deeply appreciate.

     

    Best Regards,

    David