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ONET4211LD: Modulation using OUTPOL

Eugene Kozar
Prodigy 20 points
Part Number: ONET4211LD

I don't like interfacing CML levels on DIN inputs. How about using OUTPOL as a mod input for modest speeds (<1MHz)? What is the best solution to ensure the deterministic state of the data input buffer?

  • 0
    TI__Intellectual 1715 points

    Hi Eugene,

    The modulation signal is actually routed through the path: DIN+/- to Input buffer to Current Modulator to the MOD+/- pins. The OUTPOL (LVTTL input pin) is only meant for simply changing the polarity of this modulation signal output at the o/p pins MOD+/-.

    Also, the ONET4211LD is designed for high-speed applications, with data rates between 155Mbps and 4.25Gbps. The device may work at speeds < 1Mbps but the  performance is not guaranteed at such low speeds. 

    Thanks,

    Sri  

  • 0 in reply to Sriharsha Kota Pavan
    Prodigy 20 points

    Sri,

    You don't have to explain how DINs are routed - it is clear from the datasheet block diagram. It is no brainer that changing polarity of the modulation signal (while their inputs are held at a predetermined state) has the same effect on modulation. My question is still open: will OUTPOL work up to 1MHz and how to place DINs at a predetermined state (say, DIN+ is "1" and DIN- is "0", or the opposite...). Will 5k resistor to GND on any of these inputs be sufficient?

  • 0 in reply to Eugene Kozar
    TI__Intellectual 1715 points
    We have not tested the upper limit of OUTPOL pin switching, it could work for speeds < 1 Mbps but we cannot guarantee.

    On the pin configuration: The DIN+/- must be dc coupled. Logic High voltage would be Vcc, Logic Low voltage around Vcc-0.4V. DO NOT connect the DIN+/- to ground, this would blow the input termination resistor.

    Thanks,
    Sri