Texas Instruments High Performance Frequency Synthesizer System with Integrated VCO LMX25311226EVAL/NOPB LMX25311226EVAL/NOPB Datenbogen
Produktcode
LMX25311226EVAL/NOPB
L M X 2 5 3 1 L Q 1 2 2 6 E E V A L U A T I O N B O A R D O P E R A T I N G I N S T R U C T I O N S
Troubleshooting
Problem Corrective
Actions
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All Modes
• Ensure a valid signal is presented to the OSCin connector. If a signal
generator is used, ensure the RF is ON.
• Consult the CodeLoader instructions for more detailed information on
communication issues
LPT Mode (Uses Parallel Port Cable)
• Ensure that CodeLoader is selected to LPT mode on the Port Setup tab
• Ensure the proper port number is selected (LPT1, LPT2, LPT3). CodeLoader
does NOT automatically detect this.
• Ensure the LPT cable is securely connected to the computer and board.
• Exit and Restart CodeLoader
• Ensure the parallel port is in the correct mode
o Windows often requires Administrative access to write to the parallel
port
o Ensure that the parallel port is set to “Enabled” in windows device
manager
o A reboot upon installation of CodeLoader is sometimes necessary to
get the parallel port to work.
o Standard mode is the most reliable. This can be set in the BIOS mode
of the computer as “Normal”, “Output Only”, or “AT”
USB Mode (Uses USB to Parallel Port Converter)
• On the menu, select USB->Version to verify communication with the board
• Ensure the Green LEDs are lit on the USB board
• Ensure there are no conflicts with other USB devices and reinstall the board
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• Ensure that there is a valid signal presented to the OSCin connector. If a signal
generator is used, ensure that the RF is set to ON.
• If using the lower frequency band (DIV2=1), understand that the VCO
frequency in CodeLoader should be twice the frequency at the Fout pin.
• Ensure that the VCO FREQUENCY CAL bits on the Bits/Pins tab are correct
• Ensure that the loop filter is optimized if the charge pump current, phase
detector frequency, or loop filter values have been changed from their original
settings. Ensure that the integrated loop filter components on CodeLoader are
set to their proper settings
settings. Ensure that the integrated loop filter components on CodeLoader are
set to their proper settings
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• Ensure the signal presented to OSCin connector is clean. Try another source,
or if it is a signal generator, try using a higher frequency and dividing it down to
the phase detector frequency.
the phase detector frequency.
• Ensure the OSCin signal and cable provide sufficient power level.
• If the phase detector frequency or charge pump current are lowered from their
original settings, the in-band phase noise can be degraded, even if the loop
filter is re-designed for the same loop bandwidth. If the loop bandwidth is
decreased, in-band phase noise can be degraded
filter is re-designed for the same loop bandwidth. If the loop bandwidth is
decreased, in-band phase noise can be degraded
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• Ensure the measurement equipment noise floor is not limiting the
measurement. For spectrum analyzers, the noise floor at a particular setting
can be measured by removing the RF input signal
can be measured by removing the RF input signal
• If the settings are changed from what the board was designed for, ensure the
delta-sigma modulator is not increasing the far-out noise. To know this, tune to
an integer channel and set the ORDER bit to “Reset Modulator”. The far out
phase noise should not decrease. If it does, try a loop filter with more
attenuation or select a lower order delta-sigma modulator.
an integer channel and set the ORDER bit to “Reset Modulator”. The far out
phase noise should not decrease. If it does, try a loop filter with more
attenuation or select a lower order delta-sigma modulator.
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