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National Semiconductor
National Semiconductor

LM1872 Datasheet

Radio Control Receiver/Decoder


LM1872 Datasheet Preview


February 1989
LM1872 Radio Control Receiver Decoder
General Description
The LM1872 is a complete RF receiver decoder for radio
control applications The device is well suited for use at ei-
ther 27 MHz 49 MHz or 72 MHz in controlling various toys
or hobby craft such as cars boats tanks trucks robots
planes and trains The crystal controlled superhet design
offers both good sensitivity and selectivity When operated
in conjunction with the companion transmitter LM1871 it
provides four independent information channels Two of
these channels are analog pulse width modulated (PWM)
types while the other two are simple ON OFF digital chan-
nels with 100 mA drive capability Either channel type can
be converted to the other form through simple external cir-
cuitry such that up to 4 analog or up to 4 digital channels
could be created Few external parts are required to com-
plement the self-contained device which includes local os-
cillator mixer IF detector AGC sync output drivers and all
decoder logic on-chip
Features
Y Four independent information channels two analog and
two digital
Y Completely self-contained
Y Minimum of external parts
Y Operation from 50 kHz to 72 MHz
Y Highly selective and sensitive superhet design
Y Operates from four 1 5V cells
Y Excellent supply noise rejection
Y 100 mA digital output drivers
Y Crystal controlled
Y Interfaces directly with standard hobby servos
Applications
Y Toys and hobby craft
Y Energy saving remotely switched lighting systems
Y Burgler alarms
Y Industrial and consumer remote data links
Y IR data links
Y Remote slide projector control
Circuit Block and Connection Diagram
Dual-In-Line Package
Bottom View
Order Number LM1872N
See NS Package Number N18A
TL H 7912 – 1
C1995 National Semiconductor Corporation TL H 7912
RRD-B30M115 Printed in U S A
Page 1

Absolute Maximum Ratings
If Military Aerospace specified devices are required
please contact the National Semiconductor Sales
Office Distributors for availability and specifications
Supply Voltage
7V
Package Dissipation (Note 2)
1600 mW
Voltage Pin 7 8 9 10 11 or 12
Va
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering 10 sec )
b25 C to a85 C
b65 C to a150 C
260 C
DC Electrical Characteristics
Va e 6V TA e 25 C Test Circuit of Figure 1 fL0 e 49 890 MHz fIF e 455 kHz unless otherwise specified
Parameter
Conditions
Min Typ Max
Supply Voltage
Supply Current
Functional for VIN e 100 mV
25
6
7
CH A B Off
CH A B On
9 13 18
27
VBIAS
Sync Timer Threshold
Pin 4
Pin 13 Going from
Low to High Voltage
1 85
Va 2 b 0 4
21
Va 2
2 35
Va 2 a 0 3
DIGITAL CHANNELS A AND B
Saturation Voltage
Saturation Resistance
Pins 7 9 RL e 100X
Pins 7 9
04 07
7
Source Current
Collector Pull-Up
Resistance
Pins 8 10
VPin 8 Pin 10 s 1V
Pin 7 Pin 9 to Va
100
5 10
20
Emitter Pull-Down
Resistance
Pin 8 Pin 10 to GND
5 10 20
ANALOG CHANNELS 1 AND 2
Saturation Voltage
Saturation Resistance
Pins 11 12 RL e 2 kX
Pins 11 12
0 45 0 7
160
Collector Pull-Up
Resistance
Pin 11 Pin 12 to Va
5 10 20
Units
V
mA
mA
V
V
V
X
mA
kX
kX
V
X
kX
AC Electrical Characteristics
Parameter
RF Sensitivity
RF Sensitivity
Voltage Gain
PSRR of RF Sensitivity
BW
Noise
AGC Threshold
Mixer Conversion
Transconductance
Conditions
For ‘‘Solid’’ Decoded Outputs
(Note 1)
Circuit of Figure 5 49 MHz
with Antenna Simulation
Network of Figure 6
Pin 5 to Pin 15
3V s Va s 6V
3 dB Down Pin 15
Referred to Input Pin 5 VIN e 0
Referred to IF Pin 15 VIN e 0
Onset of AGC Relative to
RF Input VIN Pin 5
Relative to IF Output Pin 15
From Pin 5 to Pin 18
1 MHz
27 MHz
49 MHz
2
Min Typ Max Units
22 39 mV
12 mV
Va a 0 07
29
58
b1
32
0 35
0 28
88
Va a 0 100
40
37
35
Va a 0 13
69
dB
%D V
kHz
mVrms
mVrms
mV
V
mmhos
mmhos
mmhos
Page 2

AC Electrical Characteristics (Continued)
Parameter
Conditions
Min Typ Max Units
Mixer Input Impedance
Pin 5 to Pin 4 49 MHz
(See Curves)
20 kX a 5 pF
Mixer Output Impedance Pin 18 to GND
250 kX
IF Transconductance
Pin 17 to Pin 15 (AGC Off) 455 kHz
26
41
5 6 mmhos
IF Input Impedance
Pin 17 to GND
5500
X
IF Output Impedance
Pin 15 to GND (AGC Off)
800 kX
(AGC On)
2 MX
IF Carrier Level
Pin 15 VIN e 100 mV
(AGC On)
70 mVrms
Detector Threshold
Relative to RF Input
VIN Pin 5
Relative to IF Output
Pin 15
Va a 0 015
20
Va a 0 025
Va a 0 040
mV
V
Analog Pulse Width
Ratio of Received Pulse Width
Accuracy
Pins 11 12 to Transmitted
Pulse Width Pin 5 for
0 95 1 0 1 05 ms ms
VIN e 100 mV
Note 1 The criteria for the outputs to be considered ‘‘solid’’ are as follows
DIGITAL In order to check the decoding section four RF frames are inputted in sequence with the proper codes to exercise all four possible logical
output combinations at pins 7 and 9 For each frame the proper output logic state must exist
ANALOG Each analog pulse width (measured at pins 11 12) in any of the above four successive frames must not vary more than g5% from the pulse
widths obtained for VIN e 100 mV
Note 2 For operation in ambient temperatures above 25 C the device must be derated based on a 150 C maximum junction temperature and a package
thermal resistance of 75 C W junction to ambient
Typical Performance Characteristics
Supply Current vs
Supply Voltage
Analog Channel Output
Voltage vs Load Current
Digital Channel
Collector Output Voltage
vs Load Current
Sensitivity vs Supply Voltage
Mixer Transconductance (gm)
vs Input Frequency
IF Output Signal Level vs RF
Input Signal Level
TL H 7912 – 2
3
Page 3
Part Number LM1872
Manufactur National Semiconductor
Description Radio Control Receiver/Decoder
Total Page 20 Pages
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