Revised
-
December 2013
LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs
SNAU126A
21
Copyright © 2013, Texas Instruments Incorporated
Recommended Test Equipment
Power Supply
The Power Supply should be a low noise power supply, particularly when the devices on the
board are being directly powered (onboard LDO regulators bypassed).
Phase Noise / Spectrum Analyzer
To measure phase noise and RMS jitter, an Agilent E5052 Signal Source Analyzer is
recommended. An Agilent E4445A PSA Spectrum Analyzer with the Phase Noise option is also
usable although the architecture of the E5052 is superior for phase noise measurements. At
frequencies less than 100 MHz the local oscillator noise of the E4445A is too high and
measurements will reflect the E4445A’s internal local oscillator performance, not the device
under test.
Oscilloscope
To measure the output clocks for AC performance, such as rise time or fall time, propagation
delay, or skew, it is suggested to use a real-time oscilloscope with at least 1 GHz analog input
bandwidth (2.5+ GHz recommended) with 50 ohm inputs and 10+ Gsps sample rate. To
evaluate clock synchronization or phase alignment between multiple clock outputs, it’s
recommended to use phase-matched, 50-ohm cables to minimize external sources of skew or
other errors/distortion that may be introduced if using oscilloscope probes.