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DAC60501: Suitability for directly driving a cable

Greg
Expert 2021 points
Part Number: DAC60501

I am planning on using the output of the DAC60501 to drive a cable with a length between 1 and 10 feet.  The CLOAD spec for the DAC looks great compared to that of op-amps I've been looking at.  Is the DAC60501 suitable for driving a cable or is there something I'm not considering?  You can assume a cable capacitance of 15 pF per foot.

Regards,

Greg

  • +1
    TI__Guru 53283 points

    I think you should consider the inductive load as well, depending on if you are going to look for fast switching or if the output is expected to handle a dynamic current load as well.

    Generally, I never recommend a DAC output be directly connect to the cable terminal.  I might be over-protective, but I recommend some small series element to help with capacitive load (5-10Ω) and if you are expending the possibility of miswiring or other shorting loads, you might consider some transient voltage protection diodes.

  • 0 in reply to Paul_Frost
    Expert 2021 points

    Thank you Paul.  I do expect fast switching because this will be driving a laser, where the voltage would often be switched between large extremes rapidly.  I would like to know how the op-amp buffer in the DAC differs from discrete op-amps TI offers.  Given the impressive CLOAD spec for the DAC, it appears the characteristics of the buffer were optimized so that it could drive large values of capacitance in sample and hold applications (there is a section on that in the datasheet).  By allowing the buffer to handle more capacitance, is there a tradeoff?  If so, what aspect of the buffer characteristics are compromised?

    You're pointing out the fact that the cable includes a significant amount of inductance, whereas a sample and hold on a PCB is mostly capacitive.  Ultimately I would be better off locating the DAC close to the laser and using digital signals to interface with the DAC.  But in the meantime I need to send an analog signal down the cable in this design, so I would like to understand the limitations.  I can see how the added resistance would form an RC filter with the cable, which would tone down the ringing.  Thank you for your insight.  It is helping me a lot in understanding how I need to approach this.

    Regards,

    Greg