lc72131m Sanyo Semiconductor Corporation, lc72131m Datasheet - Page 20

no-image

lc72131m

Manufacturer Part Number
lc72131m
Description
Am/fm Pll Frequency Synthesizer
Manufacturer
Sanyo Semiconductor Corporation
Datasheet

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LC72131M
Manufacturer:
LT
Quantity:
53
Part Number:
LC72131M
Manufacturer:
SANYO/三洋
Quantity:
20 000
Part Number:
lc72131mD-TLM-E
Manufacturer:
SANYO/三洋
Quantity:
20 000
Part Number:
lc72131mD-TLM-E
Manufacturer:
SANYO
Quantity:
5 941
Company:
Part Number:
lc72131mD-TLM-E
Quantity:
2 000
Company:
Part Number:
lc72131mD-TLM-E
Quantity:
1 896
Clock Time Base Usage Notes
The pull-up resistor used on the clock time base output pin (BO1) should be at least 100 kΩ. 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
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.
• Side band generation due to reference frequency leakage
• 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 100 dB, 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.
DZ1
0
0
1
1
DZ0
0
1
0
1
Dead zone mode
DZA
DZB
DZC
DZD
Charge pump
OFF/OFF
OFF/OFF
ON/ON
ON/ON
LC72131, 72131M
Dead zone
– –0 s
+ +0 s
–0 s
+0 s
No. 4921-20/23

Related parts for lc72131m