Chapter 10 523
Synthesizer Section
General PLL Troubleshooting
step 1, the problem is external to the PLL. For example, the
reference frequency could be faulty. If the integrator output voltage
appears incorrect, confirm that the pulses out of the phase detector
(2) are attempting to tune the oscillator in the correct direction.
3. If the phase detector output is bad, check the inputs to the detector
(3). One input should be higher in frequency than the other; this
should match the phase detector outputs.
4. Confirm proper power levels for the signals at the input to the "N"
dividers (4), the reference inputs (5 and 7), and the loop feedback
path (6).
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