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LMH1219: X7R or X5R? for 12G SDI AC coupling caps selection

Shawn_Wang
Expert 3811 points
Part Number: LMH1219


Hi team

I noticed that 4.7uF X5R AC coupling caps are used in our 12G SDI application EVM, I am wondering if you could give more explanation regarding the AC caps type.

 

My customer found an issue regarding the X5R cap in the reset circuit: when the temperature rises(<85°C), the insulation resistance of X5R will drop, this leads to some problems in reset circuits and the cap manufacturer admit the insulation resistance drop feature does exist. After changing the cap from X5R to X7R, the reset circuit work normally at high temperature (Still less than 85°C).

Hence, the customer wants to know:

  • If TI knows the insulation resistance issue of the X5R cap and if this issue will cause problems in the 12G SDI application? 
  • Why TI choose X5R caps in the 12G SDI application? when in high-temperature (<85°C) if X5R is still a suitable choice for the AC caps selection?

Due to some network problems, I can't send an email to you temporarily :(.

Look forward to your reply.

  • 0
    TI__Guru* 93570 points

    Hi Stone,

    As it relates to this issue, we have not observed a negative side effect and this has not been reported by other customers. X7R i believe are ceramic and thus have a better temperature performance but they are more expensive. Your customer can use X7R type cap if they prefer.

    Regards,, Nasser