參數(shù)資料
型號(hào)： LA17000M
元件分類： 接收器
英文描述： AM/FM, AUDIO SINGLE CHIP RECEIVER, PQFP80
封裝： 14 X 14 MM, QFP-80
文件頁(yè)數(shù)： 21/54頁(yè)
文件大?。?/td> 830K
代理商： LA17000M
LA17000M
No. 6522-28/54
Other Items
[1] Notes on the Phase Comparator Dead Zone
DZ1
DZ0
Dead zone mode
Charge pump
Dead zone
0
DZA
ON/OFF
– –0 s
0
1
DZB
ON/ON
–0 s
1
0
DZC
OFF/OFF
+0 s
1
DZD
OFF/OFF
++0 s
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/ON) 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.
Dead Zone
The phase comparator compares fp to a reference frequency (fr) as shown in Fig. 1. Although the characteristics of
this circuit (see Fig. 2) are such that the output voltage is proportional to the phase difference (line A), a region
(the dead zone) in which it is not possible to compare small phase differences occurs in actual ICs due to internal
circuit delays and other factors (line B). A dead zone as small as possible is desirable for products that must provide
a high S/N ratio.
However, since a larger dead zone makes this circuit easier to use, a larger dead zone is appropriate for popularly-
priced products. This is because it is possible for RF signals to leak from the mixer to the VCO and modulate the
VCO in popularly-priced products in the presence of strong RF inputs. When the dead zone is narrow, the circuit
outputs correction pulses and this output can further modulate the VCO and generate beat frequencies with the RF
signal.
[2] Notes on the PLL IN and HCTR pins
Coupling capacitors must be placed extremely close to these pins. The capacitance should be about 100 pF. If a
capacitor with a capacitance of 100 pF or less is not used with HCTR in particular, there will be a long wait until the
bias level is reached, which may sometimes cause miscounting.
[3] Notes on IF counting
When using the general-purpose counter for IF counting, be certain to have the microcontroller determine whether
the IF-IC SD (Station Detector) signal is present or not, and to turn on the IF count buffer output and conduct the
count, but only if the SD signal is present. Conducting an auto search using only the IF count is not reliable, since
there is a possibility of stopping even where there is no station due to leaked output from the IF count buffer.
[4] Using the DO pin
Aside from data output mode, the DO pin can also be used to check for the completion of counting by the general-
purpose counter, unlock detection output, and to check for changes in the input pins. It is also possible to input the
status of the input pins (I/O-1, I/O-2) to the controller, unchanged, via the DO pin.
Leak
Fig. 1
Fig. 2
相關(guān)PDF資料
PDF描述
LA1776M 2-BAND, AUDIO TUNER, PQFP64
LA1776M 2-BAND, AUDIO TUNER, PQFP64
LA1780M 2-BAND, AUDIO TUNER, PQFP64
LA1781M AM/FM, AUDIO SINGLE CHIP RECEIVER, PQFP64
LA1784M AM/FM, AUDIO SINGLE CHIP RECEIVER, PQFP64
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