參數(shù)資料
型號: LC72713W
廠商: SANYO SEMICONDUCTOR CO LTD
元件分類: 消費家電
英文描述: SPECIALTY CONSUMER CIRCUIT, PQFP64
封裝: 10 X 10 MM, SQFP-64
文件頁數(shù): 10/22頁
文件大小: 201K
代理商: LC72713W
LC72131K, 72131KM
No.A0788-18/22
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.
Clock Time Base Usage Notes
The pull-up resistor used on the clock time base output pin (BO1) should be at least 100k
Ω. This is to prevent
degrading the VCO C/N characteristics when a loop filter is formed using the built-in low-pass filter transistor. Since
the clock time base output pin and the low-pass filter have a common ground internal to the IC, it is necessary to
minimize the time base output pin current fluctuations and to suppress their influence on the low-pass filter. Also, to
prevent chattering we recommend using a Schmitt input at the controller (microprocessor) that receives this signal.
Other Items
[1] Notes on the Phase Comparator Dead Zone
DZ1
DZ0
Dead zone mode
Charge pump
Dead zone
0
DZA
ON/ON
- -0s
0
1
DZB
ON/ON
-0s
1
0
DZC
OFF/OFF
+0s
1
DZD
OFF/OFF
++0s
Since correction pulses are output from the charge pump even if the PLL is locked when the charge pump is in the
ON/ON state, the loop can easily become unstable. This point requires special care when designing application
circuits.
The following problems may occur in the ON/ON state.
(1) Side band generation due to reference frequency leakage
(2) Side band generation due to both the correction pulse envelope and low frequency leakage
Schemes in which a dead zone is present (OFF/OFF) have good loop stability, but have the problem that
acquiring a high C/N ratio can be difficult. On the other hand, although it is easy to acquire a high C/N ratio with
schemes in which there is no dead zone, it is difficult to achieve high loop stability. Therefore, it can be effective
to select DZA or DZB, which have no dead zone, in applications which require an FM S/N ratio in excess of 90 to
100dB, or in which an increased AM stereo pilot margin is desired. On the other hand, we recommend selecting
DZC or DZD, which provide a dead zone, for applications which do not require such a high FM signal-to-noise
ratio and in which either AM stereo is not used or an adequate AM stereo pilot margin can be achieved.
VCC
VCO
Vt
VDD
PD
AIN
AOUT
BO1
Rt
≥100kΩ
Schmitt input
Microprocessor
S
LC72131K/KM
Loop filter
Time base output
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