LMX2350 National Semiconductor Corporation, LMX2350 Datasheet - Page 18

• Manufacturer Part Number: LMX2350
• Description: Pllatinum Tm Fractional N Rf / Integer N If Dual Low Power Frequency Synthesizer
• Manufacturer: National Semiconductor Corporation

Programming Description
(Continued)
4.6 LOCK DETECT DIGITAL FILTER
The Lock Detect Digital Filter compares the difference between the phase of the inputs of the phase detector to a RC generated
delay of approximately 15nS. To enter the locked state (Lock = HIGH) the phase error must be less than the 15nS RC delay for
5 consecutive reference cycles. Once in lock (Lock = HIGH), the RC delay is changed to approximately 30nS. To exit the locked
state (Lock = LOW), the phase error must become greater than the 30nS RC delay. When the PLL is in the power down mode,
Lock is forced LOW. A flow chart of the digital filter is shown at right.
DS100831-4
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