DS90UB933-Q1: Spread Spectrum External Clock Allowed?

Mark Malik

Part Number: DS90UB933-Q1
Other Parts Discussed in Thread: DS90UB954-Q1

Is spread spectrum clocking acceptable on the 933 using an external oscillator? If yes, are there any guidelines for spread or modulation type? Specifically, would the SiT9025-AA-71-18NA30.00000 be acceptable?

-40degC to +125degC
+/- 20 ppm
Center spread & Triangular
+/- 0.125%
30MHz

https://www.sitime.com/products/automotive-high-temp-oscillators/sit9025

over 5 years ago

0 Casey McCrea over 5 years ago

TI__Guru** 103215 points

Hello Mark,

933 is not qualified for SSC - please do not apply SSC clock to the serializer.

Best Regards,

Casey

0 Chuan Gao over 5 years ago in reply to Casey McCrea

Prodigy 125 points

Hello Casey

Thanks for your reply, Is there any technical reason why SSC should not be applied?

0 Casey McCrea over 5 years ago in reply to Chuan Gao

TI__Guru** 103215 points

Hello Chuan,

The 933 PLL is not designed to track an SSC clock input so there is high risk of PLL unlock. We have newer devices which are designed to track SSC REFCLK. For example, DS90UB953-Q1->DS90UB954-Q1 can support SSC in synchronous mode with the SSC REFCLK applied to the 954 side - see the 954 datasheet.

Best Regards,

Casey

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DS90UB933-Q1: Spread Spectrum External Clock Allowed?