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Original question:

CDCE6214: Using CDCE6214RGET to feed PCIe and DDR reference inputs- guidance needed

CDCE6214: Some problem about CDCE6214 application in TDA4

Kuo Guo
Prodigy 130 points

Part Number: CDCE6214
Other Parts Discussed in Thread: CDCI6214

Hi Ti:

We have some problem about CDCE6214 application in TDA4.

1.Is it must be have 50ohm to gnd between TDA4 and CDCE6214 100MHz clock? We can see it is must be have in ref design and datasheet.But it is not must have 50ohm to gnd at LP-HCSL mode in CDCE6214 datasheet.

2.The TDA4 require software close the internal  termination before the ref clk is good,when the ref clk vpp is bigger than 400mV.And that CDCE6214 ref clk vpp is always bigger than 400mV whether in  LP-HCSL mode or  LVDS mode.

So, the software need to close the internal  termination and the TDA4 need to add external 50ohm to gnd in ref clk.Is that correct?

Is it must be conterl the  CDCE6214 not output ref clk in TDA4 power on?

3.Is the  CDCE6214 work in LP-HCSL mode or  LVDS mode with the TDA4?

And is the ref clk need to have series AC capacitance when  CDCE6214 work in LVDS mode ?

4.Is the function of series 30ohm and 50ohm to gnd between TDA4 and CDCE6214 100MHz clock in the tda4 ref design?

TDA4 DATASHEET

CDCE6214 DATASHEET 

TDA4 REF DESIGN

Thanks!!

 

  • 0
    TI__Mastermind 18070 points

    Hello,

    Please find my comments below:

    1.Is it must be have 50ohm to gnd between TDA4 and CDCE6214 100MHz clock? We can see it is must be have in ref design and datasheet.But it is not must have 50ohm to gnd at LP-HCSL mode in CDCE6214 datasheet.

    Hao: The reference design is based on CDCI6214 which requires external 50Ohm for HCSL output. CDCE6214 has internal 50Ohm termination for HCSL so the external 50Ohm should be removed.

    2.The TDA4 require software close the internal  termination before the ref clk is good,when the ref clk vpp is bigger than 400mV.And that CDCE6214 ref clk vpp is always bigger than 400mV whether in  LP-HCSL mode or  LVDS mode.

    So, the software need to close the internal  termination and the TDA4 need to add external 50ohm to gnd in ref clk.Is that correct?

    Hao: LP-HCSL by itself has intrinsic 50Ohm termination. Again the reference design is based on CDCI6214 not CDCE6214. When you use CDCE6214, make sure to remove the external 50Ohm for LP-HCSL outputs.

    Is it must be conterl the  CDCE6214 not output ref clk in TDA4 power on?

    3.Is the  CDCE6214 work in LP-HCSL mode or  LVDS mode with the TDA4?

    And is the ref clk need to have series AC capacitance when  CDCE6214 work in LVDS mode ?

    Hao: Please check with the TDA4 team on their input requirements. Normally LP-HCSL is used for PCIe reference clocks.

    4.Is the function of series 30ohm and 50ohm to gnd between TDA4 and CDCE6214 100MHz clock in the tda4 ref design?

    Hao: I'm not sure where the 30Ohm is coming from. When LP-HCSL is used, there's no need for 30Ohm series resistor nor the 50Ohm to ground termination. In fact, no external resistor is needed.

    Regards,
    Hao