LC72131 View Datasheet(PDF) - SANYO -> Panasonic

Part Name

Description

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LC72131

AM/FM PLL Frequency Synthesizer

SANYO -> Panasonic 

2. Unlock Detection Software

LC72131, 72131M

Figure 3

3. Unlocked State Data Output Using Serial Data Output

In the LC72131, once an unlocked state occurs, the unlocked state serial data (UL) will not be reset until a data input

(or output) operation is performed. At the data output x point in Figure 3, although the VCO frequency has

stabilized (locked), since no data output has been performed since the divisor N was changed the unlocked state data

remains in the unlocked state. As a result, even though the frequency has stabilized (locked), the system remains

(from the standpoint of the data) in the unlocked state.

Therefore, the unlocked state data acquired at data output x, which occurs immediately after the divisor N was

changed, should be treated as a dummy data output and ignored. The second data output (data output y) and

following outputs are valid data.

Locked State Determination Flowchart

4. Directly Outputting Unlocked State Data from the DO Pin (Set by the DO pin control data)

Since the unlocked state (high = locked, low = unlocked) is output directly from the DO pin, the dummy data

processing described in section 3 above is not required. After changing the divisor N, the locking state can be

checked after waiting at least two reference frequency periods.

No. 4921-19/23

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