LV25700PM Datasheet, PDF (25/68 Pages) Sanyo Semicon Device – For Car Radio Single chip Tuner IC

Signal Quality
LV25700PM
Signal quality uses the same path as neighboring interference detection. (The path can be changed by BIT.)
• Detection block (Smeter_AC/DETOUT) switching inside the IC according to the electric field
• Smeter_AC detection fixed at all electric fields
• DETOUT detection fixed at all electric fields
There are two output systems as follows:
• The neighboring interference detection voltage is compared by the comparator to generate the quality output
(Q-OUT: Pin 28).
• The neighboring interference detection voltage is output in a linear manner (Signal Quality: Pin 18).
Signal Quality (Pin 18) performs DC smoothing using the output impedance (1kΩ) and an external capacity.
This pin voltage is also used to control the IF filter, so care must be taken as the IF filter response will become slow if
the capacitance value is too large.
The S-meter path performs detection from before the BPF (IF filter), so there is no difference in the quality output due
to filter band fluctuation.
The DET OUT (Pin 59) path performs detection from after the BPF (IF filter), so filter band fluctuation produces a
difference in the quality output.
(The multipath signal is detected by Smeter_AC, so differences do not easily occur in Q-OUT.)
IF1=10.7MHz
75
73
1st IF
S-
meter
SD
ST
DC
SELCT
IF2=450kHz
70
MIX2
BPF
DET
10.25MHz
Neighboring
interference
detection
Control voltage
Filter
Control
AFC
Modulation
index
detection
fc=100k*3
Noise Cancellar
Multiplex
HPF=100k*4
LPF =100k*1
+
10kΩ
-
150Ω
fc=70k*1
DET OUT
60
59
NC IN
27
24
SD/ST-IND DC MONITOR
18
Signal Quality
28
Q-OUT
71
MOD_DET
1μF
No.A1709-25/68