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The difference for cable driver

mskk12
Prodigy 150 points
Other Parts Discussed in Thread: LMH0002

Greeting!

For the cable driver such as LMH0002, it can drive a 75 ohm impedance to 800mv Vpp, which means its current driving ability is about 10mA. However, many normal CML or LVPECL drivers also have this or even bigger driving capability, can we use these drivers to drive the cable? if cannot, any specialty in cable driver which enable it to do this?

Thanks a lot. 

 

  • 0
    TI__Expert 4400 points

    The LMH0002 current driving capability is actually about 28 mA.  The LMH0002 is designed to drive a DC load of 75Ω, but the AC load it drives is 37.5Ω (75Ω termination in parallel with the 75Ω cable).  The device is able to drive a voltage of up to 1V into this 37.5Ω load.  For SDI applications, the cable driver needs to supply about 22 mA in order to generate 800 mVP-P into the 75Ω coaxial cable (assuming a current source driver like the LMH0002).

    The LMH0002 cable driver is designed for SDI applications and meets the requirements of the SMPTE ST 292 and SMPTE ST 259 standards.  It drives the appropriate amplitude into 75Ω coaxial cable, with the necessary rise/fall times, overshoot, and output return loss to meet the SMPTE requirements.  You would want to make sure that any cable driver used for SDI applications is able to meet these requirements.

    Gary Melchior