LM1865N National Semiconductor, LM1865N Datasheet - Page 5

• Manufacturer Part Number: LM1865N
• Description: ADVANCED FM IF SYSTEM
• Manufacturer: National Semiconductor

Specifications of LM1865N

• Function: FM IF System
• Rf Type: FM
• Package / Case: 20-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *LM1865N; LM1865

Application Circuit
IC External Components
Component
C1
C2
C3 C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
R1
R2 R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
L1
T1
CF1 CF2
0 01 F
0 01 F
0 01 F
10 F
0 01 F
50 F
2 2 F
5 F
0 1 F
0 01 F
25 F
0 01 F
Tuner Dependent
Tuner Dependent
Meter Dependent
5k1
25k
5k
10k Pot
12k
10k
50k
3k9
62
18 H Q
TDK Electronics
TPO410-180K or equivalent
Murata SFE10 7ML or equivalent
Q
resonate w 82 pF
TOKO KAC-K2318HM or
equivalent
u l
u l
TL H 7509–5
50
70
Typical Value
10 7 MHz
10 7 MHz L to
(See Application Circuit)
10 7 MHz
AC coupling for wide band AGC input
Buffer and AGC supply decoupling
IF decoupling capacitors
Meter decoupling capacitor
AC coupling for IF output
Regulator decoupling capacitor affects S N floor
Level mute stop time constant
AFT decoupling affects stop time
Disables noise mute stop
AC coupling for noise mute stop threshold adjust
Supply decoupling
AGC output decoupling capacitor
Wide band AGC threshold adjust
Gain set and bias for IF R2
Sets full-scale on meter
Deviation mute stop window adjustment
Mute stop filter affects stop time
Level mute stop threshold adjustment
Level mute stop threshold adjustment
Noise mute stop threshold adjustment decrease resistor for lower
S N at threshold for optimum performance over temp and gain varia-
tion set this resistor value so that the signal level mute stop threshold
occurs in the radio at 45dB S N (
Load for open-collector stop output
AGC output load resistor for open-collector output
Sets Q of quadrature coil affecting THD S N and recovered audio
Optimises minimum THD
Sets signal swing across quadrature coil High Q is important to mini-
mize effect variation of Q has on both minimum THD and AFT offset
10 7 MHz quadrature coil Q
10 7 MHz ceramic resonators provide selectivity good group delay
characteristics important for low THD of system
FIGURE 3
5
UL l
a
Comments
R3
g
70
e
3 dB) in mono
330
to terminate ceramic filter
TL H 7509– 4