CDCE6214: trace impedance

Zehui Li

Part Number: CDCE6214
Other Parts Discussed in Thread: LMK3H0102

Tool/software:

Hi,

I need a 156.25Mhz reference clock for 10Gbps XFI.

1.The soc datasheet says Output Driver Type should be HCSL. I think CDCE6214 is OK though it's output type is LP-HCSL. Please double check.

2.The soc datasheet says Differential Trace Impedance should be 85 ohm. However, the differential output impedance of CDCE6214 is 100 ohm. I worry about the mismatch. Anything can I do to optimise this?

3.The soc datasheet says Common Trace Impedance should be 25 ohm. I am confused about this Common Trace Impedance. How to control it ?

over 1 year ago

0 Kadeem Samuel over 1 year ago

TI__Mastermind 23280 points

Zehui,

CDCE6214 does not support 85 Ohm impedance LP-HCSL, and this may cause an issue with reflections. My recommendation is to instead use the LMK3H0102, which can support 85 Ohm LP-HCSL.

Can you provide the SOC snippet that discusses the common trace impedance?

Thanks,
Kadeem

0 Zehui Li over 1 year ago in reply to Kadeem Samuel

Intellectual 540 points

Hi Kadeem,

There is a table about reference clock requirements. Besides this, there is no other information.

0 Kadeem Samuel over 1 year ago in reply to Zehui Li

TI__Mastermind 23280 points

Zehui,

I am not familiar with this as a specification. This impedance value may be something that Altium (or any PCB layout tool) can provide - this is how we ensure that the differential trace impedance is correct.

Thanks,

Kadeem

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CDCE6214: trace impedance