LMX2434EVAL National Semiconductor, LMX2434EVAL Datasheet - Page 5

• Manufacturer Part Number: LMX2434EVAL
• Description: EVALUATION BOARD FOR LMX2434
• Manufacturer: National Semiconductor
• Series: PLLatinum™r

Specifications of LMX2434EVAL

• Main Purpose: Timing, Frequency Synthesizer
• Utilized Ic / Part: LMX2434
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / Rohs Status: Not Compliant
• Other names: *LMX2434EVAL

LMX2434SLE EVALUATION BOARD OPERATING INSTRUCTIONS
2.0 Measurement Considerations
2.1
Phase Noise Measurement Using A Spectrum Analyzer
The phase noise characteristics of the PLL can be measured on a spectrum analyzer or a phase
noise test set. The spectrum analyzer test technique is described here. Phase noise is measured
in units of dBc/Hz. In this evaluation, the phase noise is measured at 1 kHz offset from the output
signal. For accurate close-in phase noise measurements, the offset frequency selected should be
inside the loop bandwidth on the flat portion of the curve. For integrated phase noise
measurements a phase noise analyzer is recommended.
The Code Loader software is used to set the desired frequency and to program the LMX2434SLE
device. Refer to Appendix E for more details. For phase noise measurements at fixed offset
frequencies, use an analyzer with a noise floor below the level of measurement interest. Since
they are more readily available, below is an explanation of this test technique using a spectrum
analyzer.
Tune the spectrum analyzer to the desired center frequency with the span adjusted to include the
appropriate offset frequency. Using the delta marker, the difference between the carrier and the
noise level at the desired offset frequency is measured. The video averaging feature of the
spectrum analyzer should used to better determine the noise level.
The phase noise is a 1 Hz normalized bandwidth measurement expressed in dBc/Hz. Most
modern spectrum analyzers have a feature that automatically normalizes the phase noise
measurements to a 1 Hz bandwidth. This feature gives greater measurement accuracy. For
spectrum analyzers without this feature, the normalized phase noise is equal to the noise level
relative to the carrier minus 10 * log10 [Resolution Bandwidth]. This formula does not take into
account any errors from the spectrum analyzer.
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LMX2434SLEFPEB
May 12, 2006