LMX2572LP: Rise and fall times of RF (clock) outputs

John Willison

Part Number: LMX2572LP
Other Parts Discussed in Thread: LMX2592, LMX2572

It seems that in all but the top octave of the LMX2592, the output from LMX parts is from a digital divider. The data sheets do not provide rise or fall times for these outputs. Do you have ballpark values for the LMX2572, LMX2572LP and the LMX2592 rise and fall times?

over 6 years ago

0 Lane Boyd over 6 years ago

TI__Genius 16845 points

Thanks for posting on E2E. I have assigned your post to the responsible engineer. He will respond to you soon.

Kind regards,
Lane

0 Noel Fung over 6 years ago in reply to Lane Boyd

TI__Guru** 107030 points

Hi John,

No, we don't specify the rise/fall time of the RFout. The rise/fall time at very high frequencies are difficult, if not impossible, to measure.

0 John Willison over 6 years ago in reply to Noel Fung

Prodigy 140 points

Hi Lane,

I'd recommend using an old-school sampling scope for the measurement of rise/fall times. But I get it, in an RF lab, spectrum analyzers rule the bench.

What I'm really interested in the the amplitude of the 5th harmonic (at about 6.8 GHz) on an output at 1.366 MHz. Fourier suggests about 14 dB below the carrier if the rise and fall times are really fast. Might you have a look?

Thanks,

John

0 Noel Fung over 6 years ago in reply to John Willison

TI__Guru** 107030 points

Hi John,

OK, I can take some data, stay tuned for another update.

0 Noel Fung over 6 years ago in reply to Noel Fung

TI__Guru** 107030 points

Hi John,

The 5th harmonic is measured as -19dBc.

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LMX2572LP: Rise and fall times of RF (clock) outputs