LV25700PM Datasheet, PDF (26/68 Pages) Sanyo Semicon Device – For Car Radio Single chip Tuner IC

AM FE
LV25700PM
1. AM RF AGC
The AM RF AGC system comprises two systems: N-AGC and W-AGC.
Narrow AGC: Picks up from the 2^nd MIX input.
The band to which AGC is applied is determined by the bands of the two front-end ceramic filters.
Wide AGC: Picks up from the RF block, so AGC is applied to a wide bandwidth.
C75
CF_10.7M
C77
1μF
77
AM_RF_AGC
C78
1μF _{HCC_CONT 78}
C79
1μF
RFAGC_IN ⁷⁹
BYPASS
8V
R80
30Ω
MIX_OUT2 ⁸⁰
T80
IFT_10.7M
C80
0.022μF
W
AGC
VCA
RF
AGC
N
AGC
VCA
10.7MHz
1
23456
12
C3
0.1μF
L_AM4
47μF
C4A
0.22μF
C4B
36pF
C4C
15pF
L_AM3
1m
D
R2
680Ω
FET1
CPM5905
R5
100kΩ
C5B
0.022μF
R6
470Ω
C6
0.022μF
D3
15SV251
AM RF AGC band characteristics
(reference characteristics)
AGC ANT LEVEL vs. delta FREQUENCY
center frequency = 1MHz
100
95
Wide AGC
90
85
Band:
80
Determined by
the ceramic
75
filter bands.
Narrowe AGC
70
--500 --400 --300 --200 --100 0 100 200 300 400 500
delta frequency, kHz
L_AM1
6.8μF
L_AM2
30m
AM_RF_IN
GND_RF
2. AM high band cut and detection output level adjustment method
The pin 60 AM and FM tuner output has an impedance of
12kΩ in AM mode and a hundred and several tens of ohms
in FM mode.
The high band is pre-adjusted by the internal low pass filter
(550kΩ/80pF)) and the AM detection output level is pre-
adjusted by the internal resistor (voltage-divided by 28kΩ).
To further lower the AM band, frequency characteristics can
be adjusted with capacitor C60. To lower the AM detection
output level, the level can be adjusted with resistor R60.
* The high band and the output level cannot be raised from
the initial status.
100Ω
RF_VCC(PIN2)
FM OUT
100Ω
AM OUT
100Ω
12kΩ
100Ω
28kΩ _{300Ω 300Ω}
IF_GND(PIN72)
60
R60 C60
550kΩ
80pF
3. AM low band cut adjustment method
The AM low band frequency characteristics can be adjusted
AM DET
AM_LC_AMP
with capacitor C66, which is inserted between pin 66 and _{IF AMP}
GND.
1kΩ
1kΩ
3
2
+
-
1 ^550kΩ
DET OUT
60
1kΩ 1kΩ
80pF
Fc = 1/[2π × 1kΩ × C56]
AM LC
* In FM mode this is shared with PILOT DET, so a
66
C66
capacitance value less than 0.47μF cannot be set.
PILOT DET
SEEK_ON
1.4kΩ
10Ω 100Ω
IF AGC
1
+
-
3
2
100Ω
1kΩ
IF AGC_LPF
65
C65
No.A1709-26/68