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LMH1218EVM: Video interface

ArTzy
Genius 16129 points
Part Number: LMH1218EVM
Other Parts Discussed in Thread: LMH1219, LMH1218,

Hi Experts,

Good day. I have this case from client about interfacing with LMH1219 EVM:

"I've a HD/3G test pattern generator feeding to IN0 (single ended) on the LMH1219 EVM, then passing it through out0 on the LMH1219 to In0 on a LMH1218, and finally passing the signal out on out0 (single ended) on the LMH1218 to our video system.

If i just connect the eval boards together differentially, the system does not work (was using 50 ohm rf cables) and i could not see an eye on the eye diagram on the LMH1218evm

If I single end the connection between the two evm's taking both -ve SMAs to ground via 75 ohm resistors, it worked perfectly.

We will design our pcb to accommodate this, but I am curious if I am doing something wrong or missing something, i could not find a setting on the LMH1218 single or differential inputs"

See the attachment they shared below.

Hoping for your assistance.

Thank you.

Regards,
Archie A.


  • 0
    TI__Guru* 93670 points

    Hi Archie,

    We typically use this set up and connect these two boards differentially through 100-ohm RF cable as well. Your LMH1218 shows device is not locked but there is signal detect. Suggestion is to enable manual EQ with a setting of 0x00. Also, on OUT 0 Data Select please select retimed mode. Also, on LMH1218 GUI select OUT 0 Data Select.

    Regards ,, Nasser