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LMH1297: LMH1297 application issue

Hugo Liu
Genius 5095 points
Part Number: LMH1297

Hi Sir,

Our Customer ues LMH1297 had some issue need to clarify,

Could you please share your recommend for me?

1_Why SDI signal need AC Coupling? if we are PCB trace direct to chip , any risk?

2_How  to design SDI Lightning protection? Does TI have any recommend component?

3_How to Calculation AC Coupling value? 4.7uF or 2.2uF or How to  Calculation ?

Hugo

  • 0
    TI__Guru* 93670 points

    Hi Hugo,

    1). We need AC coupling cap to make sure common mode voltage on the 50-ohm side meets device requirement. Also, on 75-ohm side this is used to prevent ground bounce.

    2). For lightening protection normally ESD protection devices with very low loading capacitors are used.

    3). AC coupling cap value depends on the data pattern run length or duration of continuous zero or one. We need to have RC time constant higher than continuous one or zero data pattern. Based on using different video data patterns, we recommend 4.7uF capacitance value.

    Regards,, Nasser