NSC LM1865N, LM1865M, LM1865MX Datasheet
TL/H/7509
LM1865 Advanced FM IF System
February 1995
LM1865 Advanced FM IF System
General Description
Reduced external component cost, improved performance,
and additonal functions are key features to the LM1865 FM
IF system. The LM1865 is designed for use in electronically
tuned radio applications. It contains both deviation and signal level stop circuitry in addition to an open-collector stop
output. The LM1865 generates a reverse AGC voltage (ie:
decreasing AGC voltage with increasing signal).
Features
Y
On-chip buffer to provide gain and terminate two ceramic filters
Y
Low distortion 0.1% typical with a single tuned quadrature coil for 100% modulation.
Y
Broad off frequency distortion characteristic
Y
Low THD at minimum AFT offset
Y
Meter output proportional to signal level
Y
Stop detector with open-collector output
Y
Adjustable signal level mute/stop threshold, controlled
either by ultrasonic noise in the recovered audio or by
the meter output
Y
Adjustable deviation mute/stop threshold
Y
Separate time constants for signal level and deviation
mute/stop
Y
Dual threshold AGC eliminates need for local/distance
switch and offers improved immunity from third order intermodulation products due to tuner overload
Y
User control of both AGC thresholds
Y
Excellent signal to noise ratio, AM rejection and system
limiting sensitivity
Block Diagram
Order Number LM1865M
or LM1865N
See NS Package Number
M20B or N20A
TL/H/7509– 1
FIGURE 1
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Supply Voltage, Pin 17 16V
Package Dissipation (Note 1) 2.0W
Storage Temperature Range
b
55§Ctoa150§C
Operating Temperature Range
b
20§Ctoa85§C
Max Voltage on Pin 16 (Stop Output) 16V
Soldering Information
Dual-In-Line Package
Soldering (10 seconds) 260
§
C
Small Outline Package
Vapor Phase (60 seconds) 215
§
C
Infrared (15 seconds) 220
§
C
See AN-450 ‘‘Surface Mounting Methods and Their Effect
on Product Reliability’’ for other methods of soldering surface mount devices.
Electrical Characteristics
Test Circuit, T
A
e
25§C, V
a
e
12V; S1 in position 2; S2 in position 1; and S3 in position 2 unless indicated otherwise
Parameter Conditions Min Typ Max Units
STATIC CHARACTERISTICS
Supply Current 33 45 mA
Pin 9, Regulator Voltage 5.7 V
Operating Voltage Range (See Note 2) 7.3 16 V
Pin 18, Output Leakage Current Pin 20 Open, V
IF
e
0, S3 in Position 1 0.1 mA
Pin 16, Stop Low Output Voltage S1 in Position 1, S2 in Position 3 0.3 V
Pin 16, Stop High Output Leakage Current S2 in Position 2, V14eV9 0.1 mA
Pin 15, Audio Output Resistance 4.7 kX
Pin 1, Buffer Input Resistance Measured at DC 350 X
Pin 3, Buffer Output Resistance Measured at DC 350 X
Pin 20, Wide Band Input Resistance Measured at DC 2 X
Pin 8, Meter Output Resistance 1kX
DYNAMIC CHARACTERISTICS f
MOD
e
400 Hz, f
o
e
10.7 MHz, Deviation
e
g
75 kHz
b
3 dB Limiting Sensitivity IF Only (See Note 3) 60 120 mVrms
Buffer Voltage Gain VINPin 1e10 mVrms at 10.7 MHz 19 22 25 dB
Recovered Audio V
IF
e
10 mVrms, V14eV9 275 320 470 mVrms
Signal-to-Noise V
IF
e
10 mVrms, V14eV9 (See Note 4) 70 84 dB
AM Rejection V14eV9
V
IF
e
1 mV, 30% AM Mod 50 60 dB
V
IF
e
10 mV, 30% AM Mod 50 60 dB
Minimum Total Harmonic Distortion V
IF
e
10 mV 0.1 0.35 %
THD at Frequency where V14eV9 V
IF
e
10 mV, Tune until V14eV9 0.1 0.45 %
(Zero AFT Offset)
THDg10 kHz from Frequency where V14eV9 V
IF
e
10 mV 0.15 %
AFT Offset Frequency for Low V
IF
e
10 mV, S2 in Position 3, f
MOD
e
0
g
50 kHz
Stop Output at Pin 16 Offsete(Frequency for Pin 16 Low)
b
(Frequency where V14eV9)
Ultrasonic Mute/Stop Level Threshold V14eV9, S1 in Position 3 (See Note 5) 60 kHz
V
IF
e
10 mV
f
MOD
e
100 kHz
S2 in Position 3
Amount of Deviation where V16
x
Low
2
Electrical Characteristics Test Circuit, T
A
e
25§C, V
a
e
12V; S1 in position 2; S2 in position 1; and S3 in
position 2 unless indicated otherwise (Continued)
Parameter Conditions Min Typ Max Units
DYNAMIC CHARACTERISTICS f
MOD
e
400 Hz, f
o
e
10.7 MHz, Deviation
e
g
75 kHz (Continued)
Pin 13 Mute/Stop Threshold Voltage V14eV9, S1 in Position 4 220 mV
S2 in Position 3
V13 where V16
x
Low
Amount of Muting (LM1965 Only) S2 in Position 4, S1 in Position 1, V
IF
e
10 mV 66 dB
Amount of Muting with Pin 13 and S1 in Position 1 0 dB
Pin 16 Grounded V14,
e
V9, V
IF
e
10 mV
Narrow Band AGC Threshold Increase IF Input until I
AGC
e
0.1 mA 100 210 300 mVrms
Pin 20
e
30 mVrms
Wide Band AGC Threshold V
IF
e
100 mVrms 5 12 22 mVrms
Increase Signal to Pin 20 until I
AGC
e
0.1 mA
Pin 18, Low Output Voltage VINPin 20e100 mV, V
IF
e
100 mVrms 0.2 0.5 V
(LM1865 and LM1965 only)
Pin 18, High Output Voltage (LM2065 only) VINPin 20e100 mV, V
IF
e
100 mVrms, (See Note 6) 11.7 V
Pin 8, Meter Output Voltage V
IF
e
10 mV 0.1 V
V
IF
e
300 mV 1.1 V
V
IF
e
3 mV 2.6 V
Note 1: Above T
A
e
25§C derate based on T
J(max)
e
150§C and i
JA
e
60§C/W.
Note 2: All data sheet specifications are for V
a
e
12V may change slightly with supply.
Note 3: When the IF is preceded by 22 dB gain in the buffer, excellent system sensitivity is achieved.
Note 4: Measured with a notch at 60 Hz and 20 Hz to 100 kHz bandwidth.
Note 5: FM modulate RF source with a 100 kHz audio signal and find what modulation level, expressed as kHz deviation, results in V16
x
12V.
Test Circuit
TL/H/7509– 2
FIGURE 2
3
Typical Performance Characteristics (from Test Circuit)
FM Limiting Characteristics
and AM Rejection
Pin 8, Meter Output Voltage
vs IF Input Level
FM Limiting Characteristics
a
THD
% THD vs OFF Tuning
(Single Tuned Quadrature
Coil)
Deviation Mute/Stop
Threshold as a Function of
AFT Load Resistor
Supply Current vs
Supply Voltage
Pin 14, AFT Current
vs Tuning
TL/H/7509– 3
Coils and ceramic filters are available from:
Toko America
1250 Feehanville Drive
Mount Prospect, IL 60056
(312) 297-0070
Murata
2200 Lake Park Drive
Smyrna, GA 30080
(404) 436-1300
4
Application Circuit
TL/H/7509– 4
FIGURE 3
IC External Components (See Application Circuit)
Component Typical Value Comments
C1 0.01 mF AC coupling for wide band AGC input
C2 0.01 mF Buffer and AGC supply decoupling
C3, C4 0.01 mF IF decoupling capacitors
C5 10 mF Meter decoupling capacitor
C6 0.01 mF AC coupling for IF output
C7 50 mF Regulator decoupling capacitor, affects S/N floor
C8 2.2 mF Level mute/stop time constant
C9 5 mF AFT decoupling, affects stop time
C10 0.1 mF Disables noise mute/stop
C11 0.01 mF AC coupling for noise mute/stop threshold adjust
C12 25 mF Supply decoupling
C13 0.01 mF AGC output decoupling capacitor
R1 Tuner Dependent Wide band AGC threshold adjust
R2, R3 Tuner Dependent Gain set and bias for IF; R2
aR3e
330X to terminate ceramic filter
R4 Meter Dependent Sets full-scale on meter
R5 5k1 Deviation mute/stop window adjustment
R6 25k Mute/stop filter, affects stop time
R7 5k Level mute/stop threshold adjustment
R8 10k Pot Level mute/stop threshold adjustment
R9 12k Noise mute/stop threshold adjustment, decrease resistor for lower
S/N at threshold, for optimum performance over temp. and gain variation, set this resistor value so that the signal level mute/stop threshold
occurs in the radio at 45dB S/N (
g
3 dB) in mono.
R10 10k Load for open-collector stop output
R11 50k AGC output load resistor for open-collector output
R12 3k9 Sets Q of quadrature coil affecting THD, S/N and recovered audio
R13 62X Optimises minimum THD
L1 18 mHQ
u
l
50@10.7 MHz Sets signal swing across quadrature coil, High Q is important to miniTDK Electronics mize effect variation of Q has on both minimum THD and AFT offset.
TPO410-180K or equivalent
T1 Q
u
l
70@10.7 MHz, L to 10.7 MHz quadrature coil: Q
UL
l
70
resonate w/82 pF
@
10.7 MHz
TOKO KAC-K2318HM or
equivalent
CF1, CF2 10.7 MHz ceramic resonators provide selectivity; good group delay
Murata SFE10.7ML or equivalent
characteristics important for low THD of system
TL/H/7509– 5
5
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