LMX2594: LMX2594 Phase Noise

ko byeongguk

Part Number: LMX2594

Tool/software:

Hi TI,

I have a question. From what I’ve read in various forum posts, when using a 10 MHz reference, having a high slew rate contributes to better phase noise performance.

Based on that, I’d like to ask:
If a square wave and a sine wave have the same phase noise on the reference, will using a sine wave as the reference input on an actual board result in worse phase noise performance compared to the simulation results from PLLATINUMSIM?

Thank you.

30 days ago

0 Noel Fung 29 days ago

TI__Guru** 108130 points

Hi Ko,

Correct.

Phase noise of the reference clock is within the loop bandwidth, so it will affect output phase noise.

Slew rate of the reference clock will affect the PLL noise, as such, higher slew rate is desired.

PLL Sim doe not model the slew rate effect, it will give you the same result for both sine and square wave input clock, as long as the phase noise of the input clock is identical.

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LMX2594: LMX2594 Phase Noise