Advance Information MC68HC(7)08KH12Rev. 1.1
112 Freescale Semiconductor
an initial frequency error, (fDES – fORIG)/fDES, of not more than ±100
percent.
NOTE: The inverse proportionality between the lock time and the reference
frequency.
In automatic bandwidth control mode, the acquisition and lock times are
quantized into units based on the reference frequency. (See 8.4.5
Manual and Automatic PLL Bandwidth Modes.) A certain number of
clock cycles, nACQ, is required to ascertain that the PLL is within the
tracking mode entry tolerance, TRK, before exiting acquisition mode. A
certain number of clock cycles, nTRK, is required to ascertain that the PLL
is within the lock mode entry tolerance, LOCK. Therefore, the acquisition
time, tACQ, is an integer multiple of nACQ/fRDV, and the acquisition to lock
time, tAL, is an integer multiple of nTRK/fRDV.
In manual mode, it is usually necessary to wait considerably longer than
tLOCKMAX before selecting the PLL clock (See 8.4.8 Base Clock
Selector Circuit.), because the factors described in 8.9.2 Parametric
Influences on Reaction Time may slow the lock time considerably.
Automatic bandwidth mode is recommended for most users.
tACQ VDDA
fRDV
-------------


8
KACQ
-------------


=
tAL VDDA
fRDV
-------------


4
KTRK
------------


=
tLOCKMAX tACQ tAL 256tVRDV
++=