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LC72121MA View Datasheet(PDF) - SANYO -> Panasonic

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LC72121MA Datasheet PDF : 24 Pages
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2. Combining with Software
Data input
CE
Divisor N
Old data
VCO
frequency
LC72121MA
New data
φError
Unlocked state output
in the serial data
Unlocked detection
pin output
Locked
Unlocked
Data output (1) Data output (2)
Locked
Figure 3 Combining with Software
3. Outputting the unlocked state data in the serial data
At the point of data output 1 in figure 3, the unlocked state data will indicate the unlocked state, since the VCO
frequency is not stable (locked) yet. In cases such as this, the application should wait at least one whole period and
then check again whether or not the frequency has stabilized with the data output 2 operation in the figure.
Applications can implement even more reliable recognition of the locked state by performing several more checks of
the state and requiring that the locked state be detected sequentially.
<Flowchart for Lock Detection>
Divisor N changed (data input)
Data output (1)
Data output (2)
Locked state check
*
NO
YES
Wait at least 2 reference frequency periods.
Valid output data is acquired by using an interval of at
least one reference frequency period.
*: Even more reliable recognition of the locked state
can be achieved by performing several checks of
the state and requiring that the locked state be
detected sequentially.
4. Directly outputting the unlocked state to the DO pin
Since the unlocked state (high level when locked, low when unlocked) is output from the DO pin, applications can
check for the locked state by waiting at least two reference frequency periods after changing the divisor N. However,
in this case also, even more reliable recognition of the locked state can be achieved by performing several checks of
the state and requiring that the locked state be detected sequentially.
No.A2009-19/24
 

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