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Nick Gray

 

Nicholas Gray

Nicholas has worked in the Semiconductor industry for over 30 years and has authored a number of published articles about data converters (ADCs and DACs) and signal integrity issues.

 

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  • Good mornin Sir,

     

    I don't if i have to post here, and if i have to post to you. If not, please forward my demand.

    I'm in design step about a video switch .. I need to switch 4 video input (not HD) to a single ouput.. (The goal is to use only one coaxial line for 4 caméras.)

    A MCU will control this chip with selection bit (easier than serial communiations I²C..)

    I don't need low power consumption. I have to care noise signals because the other part of this board will switch power relays so the design of layout will be fastidious.

    I'm looking for chips which do this and the most simple and smaller.

    I've found Intersil # HA4314BCBZHA4314BCBZ.. but i would ask you if you know other chips, other way, any ideas to do this.

    Thank you.

     

    Best regards,

    Florent ROCHAIS

    Attachments:
    imageHA4314B.pdf
  • in reply to Former Member
    Hello, Florent –

    What you are looking for is called a Video Crosspoint Switch. The configuration you want is a 4 X 1 (4 input, one output). It is possible to use a larger array (4 X 4,  8 X 4,  8 X 8, etc), but large arrays must come in larger packages and generally cost more. While better performance can usually be achieved with surface mount packages compared with through-hole packages such as DIP, this is not always true and will depend somewhat upon your board layout and component placement.

    While I am sure there are more, the video crosspoint switches I am aware of include the following:
    HA4344B from Intersil – 4 X 1, 350 MHz Bandwidth, 16-pin SOIC package
    HA4404B from Intersil – 4 X 1, 330 MHz Bandwidth, 16-pin SOIC package
    ISL59444 from Intersil – 4 X 1, 1000 MHz Bandwidth, 16-pin SOIC package
    MAX456 from Maxim – 8 X 8, 35 MHz Bandwidth, 40-pin DIP and 44-pin PLCC packages
    ADV3221 from Analog Devices – 4 X 1, 650 MHz Bandwidth, 16-pin SOIC package, Gain = 1
    ADV3222 from Analog Devices – 4 X 1, 650 MHz Bandwidth, 16-pin SOIC package, Gain = 2

     - Nick Gray
  • in reply to nickgray

    Thank you.

    I'll test 4x1 models before PCB routing.

    Would you have advices for routing of video signals ? I did not have any lesson about that at school and no colleague haf already made a PCB with videos signals. If you know a website where this is explained or maybe a lesson ...

    Anyway thank you for your help.

    Best regards,

    FLorent

  • in reply to Former Member

    Some time ago (more than 10 years ago, I wrote a technical article on this and have been unsuccessfully trying to find it. The basic idea is to use RF layout rules. Essentially, this means keeping high level signals well away from lower level signals, keeping the signal path in one board layer as much as possible, treat interconnects as transmission lines (not like simple traces), maintain a constant impedance along any all signal lines, always have a ground layer in adjacent to any signal layer (no traces in the ground layer). IF you know how to do it, you can modify some of these rules, but you absolutely must know what you are doing. There is much more that I could say, but I do not know just how to word it at this time. I will try to consider how to say it and put it into my blog.

     

    Good luck!

  • in reply to Former Member
    While I have not found the technical article I wrote in 1998 or 1999, I have found the posting of the document used for an on-line seminar on this subject that I did back in 2002. You may find it at www.national.com/appinfo/adc/files/controlling_noise.pdf. I believe that this will provide the information you need.
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