LV25700PM Datasheet, PDF (24/68 Pages) Sanyo Semicon Device – For Car Radio Single chip Tuner IC

LV25700PM
(2) IF filter neighboring interference detection
There are two detection block systems. The S-meter AC component is detected in the weak electric field (S-meter
voltage = 2V or less), and neighboring interference is detected from DET OUT in the medium electric field or more
(S-meter voltage = 2V or more).
The detection path is changed inside the IC according to the electric field.
S-meter AC component detection only or DETOUT block detection path only can also be changed by BIT at all
electric fields.
The BPF consists of a HPF with fc = 100kHz (4th order) and an LPF with fc = 100kHz (1st order). The HPF can be
selected from 50 or 100kHz, and the LPF fc can be lowered by adding a capacity to the S-meter AC (Pin 57).
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
(3) IF filter AFC detection
The IF filter band is controlled by changing the AFC voltage (Pin 45).
The AFC voltage is generated by converting the frequency offset relative to the IF frequency (450kHz) to a voltage.
Neighboring interference detection responds even when the desired signal and the interference signal are the same
level, but AFC detection responds when the interference signal level is higher than that of the desired signal.
Therefore, AFC detection is used in an auxiliary manner for portions that cannot be detected by the neighboring
interference detection path.
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.A1709-24/68