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CDCE6214-Q1: LVDS AC termination

Vidhya C
Prodigy 145 points

Part Number: CDCE6214-Q1
Other Parts Discussed in Thread: CDCI6214, CDCE6214

Hi TI team,

CDCE6214TWRGETQ1 is used for one of our design. We have observed some difference between datasheet and EVK user guide.

  • LVDS AC coupled termination as per datasheet it is 100nF capacitor and 50 ohm pull up.

  • Where as in EVK ; it is as shown below.

Can you please confirm, which termination to follow for this device?

Also, we have used this IC before in other projects as well with below circuit. Are below termination is acceptable? Do we face any signal integrity issue with these termination? Please provide your feedback on the same.

Regards,
Vidhya

  • 0
    TI__Expert 6415 points

    Vidhya,

    Our expert is currently OOO. We will get back to you with a response by EOD tomorrow.

    Best,

    Cris

  • 0 in reply to Cris Kobierowski
    TI__Mastermind 23280 points

    Vidhya,

    The EVM design supports DC LVDS, as is shown here:

    The EVM also supports HCSL. Note that the CDCE6214 uses LP-HCSL and does not require external 50-Ohm termination resistors. The CDCI6214, which is P2P, has HCSL outputs, and as such required the 50-Ohm termination resistors to GND. These are the resistors shown in the EVM. The output is just always AC-coupled (as the input to a phase noise analyzer must be AC-coupled). 

    Either of the below connection schemes are suitable for AC-coupled LVDS, from www.ti.com/.../slaa840.pdf (the first should be substituted with higher value resistors if the 100-Ohm termination is integrated into the receiver):

    The termination that you are using presently is acceptable.

    Thanks,

    Kadeem