LMX25120967EVAL/NOPB National Semiconductor, LMX25120967EVAL/NOPB Datasheet - Page 4

• Manufacturer Part Number: LMX25120967EVAL/NOPB
• Description: EVALUATION BOARD FOR LMX25120967
• Manufacturer: National Semiconductor
• Series: PLLatinum™r

Specifications of LMX25120967EVAL/NOPB

• Main Purpose: Timing, Frequency Synthesizer
• Embedded: No
• Utilized Ic / Part: LMX2512
• Primary Attributes: Single Fractional-N and Integer-N PLL with VCO
• Secondary Attributes: 967MHz, CodeLoader Graphical User Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LMX25120967EVAL; *LMX25120967EVAL/NOPB; LMX25120967EVAL

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3.1
Measure the phase noise characteristics of the PLL with spectrum analyzer or a VCO/PLL
analyzer. The phase noise plots in these instructions are from a VCO analyzer and give an
overall picture of the phase noise of the LMX2512LQ0967. The VCO analyzer provides plots of
the phase noise over a span of offset frequencies giving the designer a more complete indication
of a device’s overall phase noise performance.
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 * log
For accurate close-in phase noise measurements, the offset frequency selected should be inside
the loop bandwidth on the flat portion of the curve.
With either measurement method, VCO analyzer or spectrum analyzer, care should be taken to
ensure the noise floor of the instrument does not limit the phase noise measurement.
LMX2512LQ0967
4. Verify that jumper blocks JP1 and JP2 contain a full compliment of shunts. JP1 connects
5. Turn the DC power supply ON and adjust the voltage output to 5.0 V. Turn the DC power
6. Connect the DC power supply output to the VDD_5V port of the evaluation board. Turn
7. Run the CodeLoader software for LMX2512 register programming. Ensure proper port
Measurement Considerations
Phase Noise Measurement
the 5.0 V supply input (VDD_5V) to the on board regulator.
additional regulator circuit and TCXO are included on the layout but not placed. JP2
connects the 2.8 V regulated supply to various supply pins on the LMX2512 and the IF
VCO.
supply OFF.
the DC power supply ON.
setup and that the reference frequency matches the CodeLoader programming in the
Bits/Pins and RF and IF PLL tabs. Refer to Appendix E for more details.
LMX2512LQ0967 EVALUATION BOARD OPERATING INSTRUCTIONS
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[Resolution Bandwidth].
February 21, 2003
For convenience, an
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