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CSI-2 buffer-repeater

Stefano de Pompeis
Prodigy 130 points

Hi everybody,

I am trying to make a design where a camera with CSI-2 interface must be connected to the related receiver.

Unfortunately I can't have a straight and short connection between camera and receiver, since there are 20 or 30 cm of traces on different PCBs where the signals have to pass trough.

Perhaps, due to some reason, the impedance between two different PCB is not perfectly matching the impedance of the whole line.

So I was thinking to  use some buffer/repeater for the CSI-2 lanes (1 clock and 4 data lanes). 

I still don't understand what is I need a dedicated buffer, or if any general purpose lvds buffer is ok.  I am really confused.

Can anyone help me ?

many thanks in advance

Stefano

  • 0
    TI__Genius 10475 points
    Stefano,
    It is recommended to route the CSI-2 lanes as differential striplines with 100 ohm diff impedance and maintain the impedance to within +/-10%.

    You can refer to the device datasheet (for eg DS90UB954 datasheet www.ti.com/.../ds90ub954-q1.pdf page 153) for the CSI-2 routing guidelines.
  • 0 in reply to Palaniappan Manickam
    Prodigy 130 points
    dear Palaniappan,
    many thanks for your fast reply.

    I actually am looking for a simple buffer.
    My system is basically a camers sensor with CSI-2 output.
    This output must be connected to my receiver device which is 10-20 cm far.
    The problem is that the between the pcb where the camera is connected and the PCB where the CSI-2 receiver is located are connected trough a very bad connector, which is in half a way between the two devices (camera and device reader).

    In order to minimize the reflected waves generated by the super bad impedance discontinuity, I was thinking to put a receiver/buffer on the camera pcb, BEFORE the connector, and another one immediately after the connector of the second PCB, where the device reader is located.

    In this way, I think, the there are 3 transmission lines:

    1) camera to buffer, on the first pcb, which can be impedance controlled.
    2) buffer to buffer, where the signal must propagate in a bad connector, which fortunately is just 1 cm long.
    3) buffer to device reader, again perfectly impedance matched.

    I don't know the electrical characteristic of the CSI-2 standard, and I am wondering if there are simple buffers matching this standard needs.
    In my mind, this buffer should simply have a differential input and a differential output.

    I hope it clarifies

    many thanks for your support,

    Stefano.