RXM-315-LR
RXM-418-LR
RXM-433-LR
WIRELESS MADE SIMPLE
®
LR SERIES RECEIVER MODULE DATA GUIDE
DESCRIPTION
The LR Receiver is ideal for the wireless transfer of
0.812"
serial data, control, or command information in the
favorable 260-470MHz band. The receiver’s
advanced synthesized architecture achieves an
outstanding typical sensitivity of -112dBm, which
0.630"
RF MODULE
RXM-418-LR-S
provides a 5 to 10 times improvement in range over
LOT 10000
previous solutions. When paired with a compatible
Linx transmitter, a reliable wireless link is formed
capable of transferring data at rates of up to
10,000bps at distances of up to 3,000 feet.
0.125"
Applications operating over shorter distances or at
lower data rates will also benefit from increased link
reliability and superior noise immunity. Housed in a
Figure 1: Package Dimensions
tiny reflow-compatible SMD package, the LR Receiver module is footprint-compatible
with the popular LC-S Receiver, allowing existing users an instant path to improved
range and lower cost. No external components are required (except an antenna),
allowing for easy integration, even for engineers without previous RF experience.
FEATURES
Long range
Low cost
PLL-synthesized architecture
Direct serial interface
Data rates to 10,000bps
Qualified data output
No external components needed
Low power consumption
Wide supply range (2.7 to 5.2VDC)
Compact surface-mount package
Wide temperature range
RSSI and Power-down functions
No production tuning
APPLICATIONS INCLUDE
Remote Control
Keyless Entry
Garage / Gate Openers
Lighting Control
Medical Monitoring / Call Systems
Remote Industrial Monitoring
Periodic Data Transfer
Home / Industrial Automation
Fire / Security Alarms
Remote Status / Position Sensing
Long-Range RFID
Wire Elimination
ORDERING INFORMATION
PART #
DESCRIPTION
TXM-315-LR
Transmitter 315MHz
TXM-418-LR
Transmitter 418MHz
TXM-433-LR
Transmitter 433MHz
RXM-315-LR
Receiver 315MHz
RXM-418-LR
Receiver 418MHz
RXM-433-LR
Receiver 433MHz
EVAL-***-LR
Basic Evaluation Kit
*** = Frequency
Receivers are supplied in tubes of 25 pcs.
Revised 8/15/08
ELECTRICAL SPECIFICATIONS
Parameter
POWER SUPPLY
Operating Voltage
With Dropping Resistor
Supply Current
Power-Down Current
RECEIVER SECTION
Receive Frequency Range:
RXM-315-LR
RXM-418-LR
RXM-433-LR
Center Frequency Accuracy
LO Feedthrough
IF Frequency
Noise Bandwidth
Data Rate
Data Output:
Logic Low
Logic High
Power-Down Input:
Logic Low
Logic High
Receiver Sensitivity
RSSI / Analog:
Dynamic Range
Analog Bandwidth
Gain
Voltage With No Carrier
ANTENNA PORT
RF Input Impedance
TIMING
Receiver Turn-On Time:
Via V
CC
Via PDN
Max. Time Between Transitions
ENVIRONMENTAL
Operating Temperature Range
Designation
V
CC
I
CC
I
PDN
F
C
–
–
–
-50
–
–
–
100
0.0
V
CC
-0.4
0.0
V
CC
-0.4
-106
–
50
–
–
–
315
418
433.92
–
-80
10.7
280
–
–
–
–
–
-112
80
–
16
1.5
50
–
–
–
+50
–
–
–
10,000
0.4
V
CC
0.4
V
CC
-118
–
5,000
–
–
–
MHz
MHz
MHz
kHz
dBm
MHz
kHz
bps
VDC
VDC
VDC
VDC
dBm
dB
Hz
mV / dB
V
Ω
–
–
–
–
2,5
5
–
–
3
3
–
–
4
5
5
5
5
5
Min.
2.7
4.3
4.0
20.0
Typical
3.0
5.0
5.2
28.0
Max.
3.6
5.2
7.0
35.0
Units
VDC
VDC
mA
µA
Notes
–
1,5
–
5
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
CC
Supply Voltage V
CC
, Using Resistor
Any Input or Output Pin
RF Input
Operating Temperature
Storage Temperature
Soldering Temperature
-0.3
-0.3
-0.3
to
+3.6
to
+5.2
to
+3.6
0
-40
to
+70
-45
to
+85
+225°C for 10 seconds
VDC
VDC
VDC
dBm
°C
°C
*NOTE*
Exceeding any of the limits of this section may lead to permanent
damage to the device. Furthermore, extended operation at these maximum
ratings may reduce the life of this device.
–
–
F
IF
N
3DB
–
V
OL
V
OH
V
IL
V
IH
–
–
–
–
–
R
IN
PERFORMANCE DATA
These performance parameters
are based on module operation at
25°C from a 3.0VDC supply unless
otherwise
noted.
Figure
2
illustrates
the
connections
necessary
for
testing
and
operation. It is recommended all
ground pins be connected to the
ground plane. The pins marked NC
have no electrical connection.
5VDC
330Ω
External
Resistor
3VDC
1
2
3
4
5
6
7
8
NC
NC
NC
GND
VCC
PDN
RSSI
DATA
ANT
GND
NC
NC
NC
NC
NC
NC
16
15
14
13
12
11
10
9
Figure 2: Test / Basic Application Circuit
TYPICAL PERFORMANCE GRAPHS
Supply
RX Data
PDN
RX DATA
–
–
–
–
3.0
0.04
–
-40
7.0
0.25
10.0
–
10.0
0.50
–
+70
mSec
mSec
mSec
5,6
5,6
5
5
°
C
Table 1: LR Series Receiver Specifications
Notes
1. The LR can utilize a 4.3 to 5.2VDC supply provided a 330-ohm resistor is placed in series with VCC.
2. Into a 50-ohm load.
3. When operating from a 5V source, it is important to consider that the output will swing to well less than
5 volts as a result of the required dropping resistor. Please verify that the minimum voltage will meet the
high threshold requirement of the device to which data is being sent.
4. For BER of 10-5 at 1,200bps.
5. Characterized, but not tested.
6. Time to valid data output.
Figure 3: Turn-On Time from V
CC
5.40
Figure 4: Turn-On Time from PDN
5.35
RFIN >-35dBm
NO RFIN
Supply Current (mA)
5.30
5.25
With Dropping
Resistor
5.20
*CAUTION*
This product incorporates numerous static-sensitive components.
Always wear an ESD wrist strap and observe proper ESD handling
procedures when working with this device. Failure to observe this
precaution may result in module damage or failure.
Page 2
5.15
5.10
2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2
Supply Voltage (VDC)
Figure 5: Consumption vs. Supply
Figure 6: RSSI Response Time
Page 3
PIN ASSIGNMENTS
1
2
3
4
5
6
7
8
NC
NC
NC
GND
VCC
PDN
RSSI
DATA
ANT
GND
NC
NC
NC
NC
NC
NC
16
15
14
13
12
11
10
9
MODULE DESCRIPTION
The LR receiver is a low-cost, high-performance synthesized AM / OOK receiver,
capable of receiving serial data at up to 10,000bps. Its exceptional sensitivity
results in outstanding range performance. The LR’s compact surface-mount
package is friendly to automated or hand production. LR Series modules are
capable of meeting the regulatory requirements of many domestic and
international applications.
50Ω RF IN
(Antenna)
Band Select
Filter
LNA
90˚
0˚
10.7MHz
IF Filter
Data Slicer
-
Limiter
+
RSSI/Analog
Data Out
∑
VCO
Figure 7: LR Series Receiver Pinout (Top View)
PIN DESCRIPTIONS
PLL
Pin #
1
2
3
4
5
Name
NC
NC
NC
GND
V
CC
Description
No Connection
No Connection
No Connection
Analog Ground
Supply Voltage
Power Down. Pulling this line low will place the receiver
into a low-current state. The module will not be able to
receive a signal in this state.
Received Signal Strength Indicator. This line will supply an
analog voltage that is proportional to the strength of the
received signal.
Digital Data Output. This line will output the demodulated
digital data.
No Connection
No Connection
No Connection
No Connection
No Connection
No Connection
Analog Ground
50-ohm RF Input
XTAL
Figure 8: LR Series Receiver Block Diagram
THEORY OF OPERATION
The LR receiver is designed to recover
data sent by an AM or Carrier-Present
Carrier-Absent (CPCA) transmitter, also
Data
referred to as CW or On-Off Keying
(OOK). This type of modulation
Carrier
represents a logic low ‘0’ by the absence
of a carrier and a logic high ‘1’ by the
presence of a carrier. This modulation
method affords numerous benefits. The
Figure 9: CPCA (AM) Modulation
two most important are: 1) cost-effectiveness due to design simplicity and 2)
higher allowable output power and thus greater range in countries (such as the
U.S.) that average output power measurements over time. Please refer to Linx
Application Note AN-00130 for a further discussion of modulation techniques.
The LR receiver utilizes an advanced single-conversion superheterodyne
architecture. Transmitted signals enter the module through a 50-ohm RF port
intended for single-ended connection to an external antenna. RF signals
entering the antenna are filtered and then amplified by an NMOS cascode Low
Noise Amplifier (LNA). The filtered, amplified signal is then down-converted to a
10.7MHz Intermediate Frequency (IF) by mixing it with a low-side Local
Oscillator (LO). The LO frequency is generated by a Voltage Controlled
Oscillator (VCO) locked by a Phase-Locked Loop (PLL) frequency synthesizer
that utilizes a precision crystal reference. The mixer stage incorporates a pair of
double-balanced mixers and a unique image rejection circuit. This circuit, along
with the high IF frequency and ceramic IF filters, reduces susceptibility to
interference. The IF frequency is further amplified, filtered, and demodulated to
recover the baseband signal originally transmitted. The baseband signal is
squared by a data slicer and output to the DATA pin. The architecture and quality
of the components utilized in the LR module enable it to outperform many far
more expensive receiver products.
Page 5
6
PDN
7
RSSI
8
9
10
11
12
13
14
15
16
Page 4
DATA
NC
NC
NC
NC
NC
NC
GND
RF IN
POWER SUPPLY REQUIREMENTS
The module does not have an internal voltage regulator, therefore it requires a
clean, well-regulated power source. While it is preferable to power the unit from
a battery, it can also be operated from a power supply as long as noise is less
than 20mV. Power supply noise can significantly affect the receiver sensitivity,
therefore; providing clean power to the module should be a high priority during
design.
Vcc TO
A 10Ω resistor in series with the supply followed by a
10µF tantalum capacitor from V
CC
to ground will help
in cases where the quality of the supply power is poor.
Operation from 4.3V to 5.2V requires an external
330Ω series resistor to prevent V
CC
from exceeding
3.6V. These values may need to be adjusted
depending on the noise present on the supply line.
MODULE
10Ω
Vcc IN
+
THE DATA OUTPUT
The CMOS-compatible data output is normally used to drive a digital decoder IC
or a microprocessor that is performing the data decoding. In addition, the module
can be connected to an RS-232 level converter chip, like the MAX232, to a Linx
USB module for interfacing to a PC, or to a standard UART. Since a UART uses
high marking to indicate the absence of data, a designer using a UART may wish
to insert a logic inverter between the data output of the receiver and the UART.
The receiver’s output may appear to switch randomly in the absence of a
transmitter. This is a result of the receiver sensitivity being below the noise floor
of the board. This noise can be handled in software by implementing a noise-
tolerant protocol as described in Application Note AN-00160. If a software
solution is not appropriate, the squelch circuit in the figure below can be used
and the designer can make a compromise between noise level and range.
VCC
R2
500k
10μF
Figure 10: Supply Filter
USING THE PDN PIN
The Power Down (PDN) line can be used to power down the receiver without the
need for an external switch. This line has an internal pull-up, so when it is held
high or simply left floating, the module will be active.
When the PDN line is pulled to ground, the receiver will enter into a low-current
(<40µA) power-down mode. During this time the receiver is off and cannot
perform any function. It may be useful to note that the startup time coming out of
power-down will be slightly less than when applying V
CC
.
The PDN line allows easy control of the receiver state from external components,
like a microcontroller. By periodically activating the receiver, checking for data,
then powering down, the receiver’s average current consumption can be greatly
reduced, saving power in battery-operated applications.
Note:
The voltage on the PDN line should not exceed V
CC
. When used with a higher
voltage source, such as a 5V microcontroller, an open collector line should be used or a
diode placed in series with the control line. Either method will prevent damage to the
module by preventing 5V from being placed on the PDN line, while allowing the line to be
pulled low.
RSSI
C1
0.1μ
VCC
VCC
2
R3
200k
1
3
DATA
5
VCC
2
D1
-
+
8
1
R1
2M
U1
4 LMV393
3
6
U2
MAX4714
Figure 11: LR Receiver and LS Decoder
RECEIVING DATA
Once an RF link has been established, the challenge becomes how to effectively
transfer data across it. While a properly designed RF link provides reliable data
transfer under most conditions, there are still distinct differences from a wired link
that must be addressed. Since the LR modules do not incorporate internal
encoding / decoding, the user has tremendous flexibility in how data is handled.
It is always important to separate what types of transmissions are technically
possible from those that are legally allowable in the country of intended
operation. Application Notes AN-00125 and AN-00140 should be reviewed along
with Part 15, Section 231 for further details on acceptable transmission content.
If you want to transfer simple control or status signals, such as button presses or
switch closures, and your product does not have a microprocessor on board or
you wish to avoid protocol development, consider using an encoder and decoder
IC set. These chips are available from a wide range of manufacturers including
Linx, Microchip, and Holtek. These chips take care of all encoding and decoding
functions and generally provide a number of data pins to which switches can be
directly connected. In addition, address bits are usually provided for security and
to allow the addressing of multiple receivers independently. These ICs are an
excellent way to bring basic remote control / status products quickly and
inexpensively to market. Additionally, it is a simple task to interface with
inexpensive microprocessors such as the Microchip PIC or one of many IR,
remote control, DTMF, and modem ICs.
Page 7
USING THE RSSI PIN
The receiver’s Received Signal Strength Indicator (RSSI) line serves a variety of
functions. This line has a dynamic range of 80dB (typical) and outputs a voltage
proportional to the incoming signal strength. It should be noted that the RSSI
levels and dynamic range will vary slightly from part to part. It is also important
to remember that RSSI output indicates the strength of any in-band RF energy
and not necessarily just that from the intended transmitter; therefore, it should be
used only to qualify the level and presence of a signal.
The RSSI output can be utilized during testing or even as a product feature to
assess interference and channel quality by looking at the RSSI level with all
intended transmitters shut off. The RSSI output can also be used in direction-
finding applications, although there are many potential perils to consider in such
systems. Finally, it can be used to save system power by “waking up” external
circuitry when a transmission is received or crosses a certain threshold. The
RSSI output feature adds tremendous versatility for the creative designer.
Page 6
+
Squelched Data
R4
5M
PROTOCOL GUIDELINES
While many RF solutions impose data formatting and balancing requirements,
Linx RF modules do not encode or packetize the signal content in any manner.
The received signal will be affected by such factors as noise, edge jitter, and
interference, but it is not purposefully manipulated or altered by the modules.
This gives the designer tremendous flexibility for protocol design and interface.
Despite this transparency and ease of use, it must be recognized that there are
distinct differences between a wired and a wireless environment. Issues such as
interference and contention must be understood and allowed for in the design
process. To learn more about protocol considerations, we suggest you read Linx
Application Note AN-00160.
Errors from interference or changing signal conditions can cause corruption of
the data packet, so it is generally wise to structure the data being sent into small
packets. This allows errors to be managed without affecting large amounts of
data. A simple checksum or CRC could be used for basic error detection. Once
an error is detected, the protocol designer may wish to simply discard the corrupt
data or implement a more sophisticated scheme to correct it.
TYPICAL APPLICATIONS
Figure 12 shows a circuit using the Linx LICAL-DEC-MS001 decoder. This chip
works with the LICAL-ENC-MS001 encoder to provide simple remote control
capabilities. The decoder will detect the transmission from the encoder, check for
errors, and if everything is correct, the encoder’s inputs will be replicated on the
decoder’s outputs. This makes sending key presses very easy.
SWITCHED OUTPUT
RELAY
VCC
VCC
10k 2.2k
220
GND
1
2
3
4
5
6
7
8
9
10
D6
D7
SEL_BAUD0
SEL_BAUD1
GND
GND
LATCH
RX_CNTL
TX_ID
MODE_IND
LICAL-DEC-MS001
D5
D4
D3
D2
VCC
VCC
D1
D0
DATA_IN
LEARN
20
19
18
17
16
15
14
13
12
11
100k
GND
VCC
VCC
GND
1
2
3
4
5
6
7
8
NC
NC
NC
GND
VCC
PDN
RSSI
DATA
RXM-LR
ANT
GND
NC
NC
NC
NC
NC
NC
16
15
14
13
12
11
10
9
GND
INTERFERENCE CONSIDERATIONS
The RF spectrum is crowded and the potential for conflict with other unwanted
sources of RF is very real. While all RF products are at risk from interference, its
effects can be minimized by better understanding its characteristics.
Interference may come from internal or external sources. The first step is to
eliminate interference from noise sources on the board. This means paying
careful attention to layout, grounding, filtering, and bypassing in order to
eliminate all radiated and conducted interference paths. For many products, this
is straightforward; however, products containing components such as switching
power supplies, motors, crystals, and other potential sources of noise must be
approached with care. Comparing your own design with a Linx evaluation board
can help to determine if and at what level design-specific interference is present.
External interference can manifest itself in a variety of ways. Low-level
interference will produce noise and hashing on the output and reduce the link’s
overall range.
High-level interference is caused by nearby products sharing the same
frequency or from near-band high-power devices. It can even come from your
own products if more than one transmitter is active in the same area. It is
important to remember that only one transmitter at a time can occupy a
frequency, regardless of the coding of the transmitted signal. This type of
interference is less common than those mentioned previously, but in severe
cases it can prevent all useful function of the affected device.
Although technically it is not interference, multipath is also a factor to be
understood. Multipath is a term used to refer to the signal cancellation effects
that occur when RF waves arrive at the receiver in different phase relationships.
This effect is a particularly significant factor in interior environments where
objects provide many different signal reflection paths. Multipath cancellation
results in lowered signal levels at the receiver and, thus, shorter useful distances
for the link.
Page 8
Figure 12: LR Receiver and MS Decoder
Figure 13 shows a typical RS-232 circuit using the LR receiver and a Maxim
MAX232 chip. The LR will output a serial data stream and the MAX232 will
convert that to RS-232 compliant signals.
VCC
C1
4.7uF
VCC
+
C2
4.7uF
C3
4.7uF
+
C4
4.7uF
+
Figure 13: LR Receiver and MAX232 IC
Figure 14 shows an example of combining the LR Series receiver with a Linx
SDM-USB-QS-S USB module. The LR will output a serial data stream and the
USB module will convert that to low-speed USB compliant signals.
USB-B
GND
DAT+
DAT -
5V
4
GSHD
GSHD
6
5
GND GND
Figure 14: LR Receiver and Linx USB Module
Page 9
+
C5
4.7uF
GND
+
MAX232
1
2
4
5
7
8
C1+
V+
C1-
C2+
V-
T2OUT
R2IN
GND
VCC
GND
16
15
DB-9
GND
1
6
2
3
8
9
5
VCC
RXM-XXX-LR-S
2
NC
NC
ANT
GND
NC
NC
NC
NC
NC
NC
C
RSSI
DATA
8
GND
GND
16
15
14
13
12
11
10
9
GND
1
2
3
4
5
6
7
8
SDM-USB-QS-S
USBDP
USBDM
GND
VCC
SUSP_IND
RX_IND
TX_IND
485_TX
RI
RXM-XXX-LR-S
16
15
VCC
1
2
NC
C
DTR
DATA
ANT
GND
NC
NC
NC
NC
NC
NC
16
15
14
13
12
11
10
9
GND
Microcontroller MCU
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