Rs-170 Buffer for long cable

Hi,

We're designing with the ADV7123 Video DAC to implement  RS-170 video signal,

the video signal should drive more then a 10 Meters cable and according to the Datasheet it's recommended to use buffers such as the AD848,

Do we need to connect the buffer to a dual supply voltage (negative and positive) to support the RS-170 signal?

Can you recommend on such application?

Thanks in advance,

Barak

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  • Hi, Barak.

    Apologies for the very late reply.

    The AD848 was rated to work with a minimum supply of +/-4.5V so if you want a single supply, +9V is the minimum supply you need. Figure 27 of the ADV7123 shows the configuration of AD848 as an output buffer. Please take note that as you use +9V, your output will only be limited to 2V (rload=150ohms) so even though you have a gain of 2, your output will still be 2V. To have a higher output voltage, better use a dual supply for the buffer. 

    Figure 26 of the ADV7123 shows the connections of ADV7123 using a Gray scale (also called the RS-170) video format as input.

    Regards,

    Anna

Reply
  • Hi, Barak.

    Apologies for the very late reply.

    The AD848 was rated to work with a minimum supply of +/-4.5V so if you want a single supply, +9V is the minimum supply you need. Figure 27 of the ADV7123 shows the configuration of AD848 as an output buffer. Please take note that as you use +9V, your output will only be limited to 2V (rload=150ohms) so even though you have a gain of 2, your output will still be 2V. To have a higher output voltage, better use a dual supply for the buffer. 

    Figure 26 of the ADV7123 shows the connections of ADV7123 using a Gray scale (also called the RS-170) video format as input.

    Regards,

    Anna

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