DS90CF386: PxCLK out issue

Tseng Roger

Part Number: DS90CF386

Hi sir,

We use the DS90CF386 to convert LVDS of NXP iMX6 to RGB888 interface. IMX6 spec: https://www.nxp.com/docs/en/data-sheet/IMX6DQIEC.pdf

The frequency setting of LVDS and PCLK is 80MHz, but the frequency of PxCLK out is 133-136MH. What is wrong?

Here is schematic.SCHEMATIC1 _ LVDS BRIDGE.pdf

over 6 years ago

0 Bryan Kahler over 6 years ago

TI__Mastermind 25955 points

Hi Tseng,

Please share and confirm the display timing parameters being utilized here:

RGB888 (24 bit)

• H_Active = ____

• H_Blank = ____

• V_Active = ____

• V_Blank = ____

• f_Vertical = _____ Hz

Sincerely,
Bryan Kahler

0 Tseng Roger over 6 years ago in reply to Bryan Kahler

Intellectual 500 points

Hi Bryan,

Here is setting parameters, please help to review it. Thanks a lot.

         clock-frequency = <74250000>;
               hactive = <1280>;
               vactive = <720>;
               hback-porch = <220>;
               hfront-porch = <110>;
               vback-porch = <20>;
               vfront-porch = <5>;
               hsync-len = <40>;
               vsync-len = <20>;

0 Tseng Roger over 6 years ago in reply to Tseng Roger

Intellectual 500 points

Hi Bryan,

We add 100 ohm termination resistors in data and clk pairs, the DS90CF386 works normally.

BR,

Roger

0 Bryan Kahler over 6 years ago in reply to Tseng Roger

TI__Mastermind 25955 points

Hi Roger,

Good to hear. Please make sure the termination resistors are located close to the RX inputs (unless fly-by termination is being utilized).

In addition to the termination resistors on the RxINn+/- and RxCLKIN+/-, please also check the power rails to ensure that noise on Vcc does not exceed 100 mVpp.

Here is a good document that describes generalized pcb recommendations for lvds:http://www.ti.com/lit/an/snla002/snla002.pdf

It may be helpful to take a quick pass over the layout to ensure it conforms to the recommendations given in the document listed above.

Sincerely,
Bryan Kahler

Interface

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DS90CF386: PxCLK out issue