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LMH0344: SMPTE Video Switcher

Andrei Ziganshin
Prodigy 15 points
Part Number: LMH0344
Other Parts Discussed in Thread: LMH0397, TMUXHS4212, TMUX1511, LMH0318, LMH0324

Tool/software:

Hi,

I'm currently designing a 2:1 SDI switch which must be capable of SDI-HD to SDI-3G . The SDI terminals are 75 Ohm.

My design consists of LMH0344SQ cable equilizer on each of the inputs and "TMUXHS4212IRKSR" is used for SDI switching (and from my understanding this chip does jitter compensation as well).

This switch will be used with cables of less than 20m distance (primarily <5m).

My questions are as follows:

1) Do I require a cable driver chip such as "LMH0302SQ" or "LMH0303SQ" after cable equilization "LMH0344SQ"?

2) What is the best design structure for the switch? Equilizer --> Cable Driver --> Reclocker? Do I require reclocker at any stage of my block diagram? I have already watched the following video (https://www.youtube.com/watch?v=zOUj4FpR18E) but would like to confirm what are the essentials for my switch as we are trying to fit into a certain budget. Please suggest the most budget chips for this application. 

3) Is it possible to minimise the design to 1 cable equilization chip and 1 cable driver (as it is a 2:1 switch and only 1 signal is used at a time). I was thinking to implement this by doing the switching using "TMUXHS4212IRKSR" as the first step of the circuit and on the 2nd step cable equilizer ending by last step cable driver and final output to the monitor?

Thank you!

  • 0
    TI__Guru* 93670 points

    Hi Eric,

    Please consider using two LMH0397 devices for this application: One is configured as cable equalizer(instead of LMH0344) and another to provide two SDI outputs. Then through pin setting or register control you can turn on one or another SDI outputs.

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 15 points

    Hi Nasser, 

    Just would like to confirm that a single LMH0397 is capable of equilizing 2 separate inputs? Or do I connect the first two inputs (INPUT1, INPUT2) to LMH0397 which is configured as Cable Driver mode for switching first and then cable equilizer as the last step before the output? 

    The reason why I've chosen TMUXHS4212 is because it it very convenient for me as it has 2 output and 4 inputs. In my application I need to control 2 sets of inputs which are totally independent of each other with their own outputs but needs to switch at the same time (please see state diagram). One set is for video and another is just for continuity. But I would like to control them with a momentary switch, please find a state diagram for your understanding of my need ("mom" is a momentary switch, mom=1 --> pressed, mom=0 --> not pressed). Is there any more suitable suggestions for this application? At the moment I'm considering to use a microcontroller with your above described setup of 2 --> LMH0397 chips as well as 1 --> TMUX1511 only for my second output (OUTPUT2). I'm trying to minimise my BOM and find the best solution for this application. Thank you! I appreciate your help.

    To confirm my I/O configuration please find a block diagram below where I outlined inputs and outputs as I need (do not look at LMH0324 and LMH0318 chips as this picture was initially taken from another post...):

     

  • 0 in reply to Andrei Ziganshin
    TI__Expert 6980 points

    Hi Andrei,

    Andrei Ziganshin said:
    Just would like to confirm that a single LMH0397 is capable of equilizing 2 separate inputs? Or do I connect the first two inputs (INPUT1, INPUT2) to LMH0397 which is configured as Cable Driver mode for switching first and then cable equilizer as the last step before the output? 

    It is recommended to use a single equalizer per input. It would be possible to route both inputs to a single equalizer, but that would require an additional Mux or Crosspoint to enable the switching.  For the equalization an LMH0324, LMH0397 or LMH0344 would work. The process is equalization first then cable driving.

    Andrei Ziganshin said:
    Is there any more suitable suggestions for this application?

    A possible suggestion is to use the crosspoint switch DS25CP104A  in the middle to save on cable drivers.

    The crosspoint switch allows IN0 and IN1 to be routed to Out0 depending on the SXX pins.

    Best,

    Nick