TXM-315-LR
TXM-418-LR
TXM-433-LR
WIRELESS MADE SIMPLE
®
LR SERIES TRANSMITTER MODULE DATA GUIDE
DESCRIPTION
The LR Series transmitter is ideal for the cost-
effective wireless transfer of serial data, control, or
command information in the favorable 260-470MHz
band. When paired with a compatible Linx receiver, a
reliable wireless link is formed, capable of
transferring serial data at rates of up to 10,000bps at
distances of up to 3,000 feet. Applications operating
over shorter distances or at lower data rates will also
benefit from increased link reliability and superior
noise immunity. The transmitter’s synthesized
architecture delivers outstanding stability and
frequency accuracy and minimizes the affects of
antenna pulling. Housed in a tiny reflow-compatible
SMD package, the transmitter requires no external
RF components (except an antenna), which greatly
simplifies integration and lowers assembly costs.
0.360"
RF MODULE
TXM-418-LR
LOT 2000
0.500"
0.130"
Typ.
Figure 1: Package Dimensions
FEATURES
n
Long range
n
n
n
n
n
Low cost
PLL-synthesized architecture
Direct serial interface
Data rates to 10,000bps
No external RF components needed
n
n
n
n
n
n
Low power consumption
Low supply voltage (2.1 to 3.6VDC)
Compact surface mount package
Wide temperature range
Power-down function
No production tuning
APPLICATIONS INCLUDE
n
n
n
n
n
n
n
n
n
n
n
n
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
Transmitters are supplied in tubes of 50 pcs.
Revised 3/4/10
ELECTRICAL SPECIFICATIONS
Parameter
POWER SUPPLY
Operating Voltage
Supply Current:
Logic High
Logic Low
Power-Down Current
TRANSMITTER•SECTION
Transmit Frequency Range:
TXM-315-LR
TXM-418-LR
TXM-433-LR
Center Frequency Accuracy
Output Power
Output Power Control Range
Harmonic Emissions
Data Rate
Data Input:
Logic Low
Logic High
Power Down Input:
Logic Low
Logic High
ANTENNA PORT
RF Output Impedance
TIMING
Transmitter Turn-On Time:
Via V
CC
or PDN
Modulation Delay
ENVIRONMENTAL
Operating Temperature Range
–
-40
–
+85
–
–
–
–
1.0
–
–
30.0
mSec
nS
4
4
4
R
OUT
–
50
–
Ω
4
V
IL
V
IH
–
V
CC
-0.25
–
–
0.25
–
VDC
VDC
–
–
V
IL
V
IH
–
V
CC
-0.25
–
–
0.25
–
VDC
VDC
–
–
–
P
O
–
P
H
–
F
C
–
–
–
-50
-4
-80
–
DC
315
418
433.92
–
0.0
–
–
–
–
–
–
+50
+4
+10
-36
10,000
MHz
MHz
MHz
kHz
dBm
dB
dBc
bps
–
–
–
–
2
3
–
–
I
PDN
V
CC
I
CC
2.1
–
–
–
–
3.0
3.4
5.1
1.8
5.0
3.6
–
–
–
–
VDC
mA
mA
mA
nA
–
1,2
2
–
–
Designation
Min.
Typical
Max.
Units
Notes
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.
VCC
GND
DATA
VCC
PDN
VCC
GND
GND
750
LADJ/VCC ANT
Figure 2: Test / Basic Application Circuit
TYPICAL PERFORMANCE GRAPHS
1. 500mV/div
2. 2.00V/div
ASK RF Output
1
TX Data
2
100nS/div
Figure 3: Modulation Delay
12
10
LADJ Resistance (kΩ)
8
6
4
°
C
2
Table 1: LR Series Transmitter Electrical Specifications
Notes
1.
2.
3.
4.
With a 50% duty cycle.
With a 750Ω resistor on LADJ.
See graph on Page 3.
Characterized, but not tested.
4.5
0
9.00
6.00
3.00
0.00
-3.00
-6.00
-9.00
Output Power (dBm)
-12.00
-15.00
-18.00
-21.00
Figure 4: Output Power vs. LADJ Resistance
Current Consumption (mA)
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
CC
Any Input or Output Pin
Operating Temperature
Storage Temperature
Soldering Temperature
-0.3
-0.3
-40
-40
to
+3.6
to V
CC
+ 0.3
to
+85
to
+90
+225°C for 10 seconds
VDC
VDC
°C
°C
4
3.5
3
2.5
*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.
Page 2
2
6.00
3.00
0.00
-3.00
-9.00
-6.00
Output Power (dBm)
-12.00
-15.00
-18.00
-21.00
Figure 5: Current Consumption vs. Output Power (50% Duty Cycle)
Page 3
PIN ASSIGNMENTS
MODULE DESCRIPTION
1
2
3
4
GND
PDN
DATA
VCC
GND
GND
LADJ/VCC ANT
8
7
6
5
Figure 5: LR Series Transmitter Pinout (Top View)
PIN DESCRIPTIONS
Pin #
1
2
3
The LR transmitter is a low-cost, high-performance synthesized ASK / OOK
transmitter, capable of sending serial data at up to 10,000bps. Because the
transmitter is completely self-contained, requiring an antenna as the only
additional RF component, application is extremely straightforward and assembly
and testing costs are reduced. When combined with an LR Series receiver, a
reliable serial link is formed capable of transferring data over line-of-site
distances of up to 3,000 feet. The LR is housed in a compact surface-mount
package that integrates easily into existing designs and is equally friendly to
prototyping and volume production. The module’s low power consumption
makes it ideal for battery-powered products. The transmitter is compatible with
many other Linx receiver products, including the LC, LR, KH, and OEM product
families. For applications where range is critical, the LR receiver is the best
choice due to its outstanding sensitivity. LR Series modules are capable of
meeting the regulatory requirements of domestic and international applications.
THEORY OF OPERATION
Description
Analog Ground
Digital Data Input
Analog Ground
DATA
PDN
Name
GND
DATA
GND
4
LADJ/V
CC
Level Adjust. This line can be used to adjust the output
power level of the transmitter. Connecting to V
CC
will give
the highest output, while placing a resistor to V
CC
will lower
the output level (see Figure 4 on Page 3).
50-ohm RF Output
PLL
VCO
PA
RF OUT
XTAL
Figure 6: LR Series Transmitter Block Diagram
5
6
7
ANT
GND
V
CC
Analog Ground
Supply Voltage
Power Down. Pulling this line low will place the transmitter
into a low-current state. The module will not be able to
transmit a signal in this state.
The LR Series transmitter is designed to generate 1mW of output power into a
50-ohm single-ended antenna while suppressing harmonics and spurious
emissions to within legal limits. The transmitter is comprised of a VCO locked by
a frequency synthesizer that is referenced to a high precision crystal. The output
of the VCO is amplified and buffered by an internal power amplifier. The amplifier
is switched by the incoming data to produce a modulated carrier. The carrier is
filtered to attenuate harmonics and then output to free space via the 50-ohm
antenna port.
The synthesized topology makes the module highly immune to the effects of
antenna port loading and mismatch. This reduces or eliminates frequency
pulling, bit contraction, and other negative effects common to low-cost
transmitter architectures. It also allows for reliable performance over a wide
operating temperature range. Like its companion LR Series receiver, the LR
Series transmitter delivers a significantly higher level of performance and
reliability than the LC Series or other SAW-based devices, yet remains very
small and cost-effective.
Page 5
8
PDN
*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 4
THE DATA INPUT
The CMOS-compatible data input on Pin 2 is normally supplied with a serial bit
stream from a microprocessor or encoder, but it can also be used with standard
UARTs.
When a logic ‘1’ is present on the DATA line and the PDN line is high, then the
Power Amplifier (PA) will be activated and the carrier frequency will be sent to
the antenna port. When a logic ‘0’ is present on the DATA line or the PDN line is
low, the PA is deactivated and the carrier is fully suppressed.
The DATA line should always be driven with a voltage that is common to the
supply voltage present on Pin 7 (V
CC
). The DATA line should never be allowed
to exceed the supply voltage, as permanent damage to the module could occur.
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 affect the
transmitter modulation; therefore, providing a clean
Vcc TO
MODULE
power supply for the module should be a high priority
during design.
10Ω
+
USING THE PDN PIN
The transmitter’s Power Down (PDN) line can be used to power down the
transmitter without the need for an external switch. It allows easy control of the
transmitter’s state from external components, such as a microcontroller. By
periodically activating the transmitter, sending data, then powering down, the
transmitter’s average current consumption can be greatly reduced, saving power
in battery operated applications.
The PDN line does not have an internal pull-up, so it will need to be pulled high
or tied directly to V
CC
to turn on the transmitter. The pull-up should be a minimum
of 30μA (10kΩ or less). When the PDN line is pulled to ground, the transmitter
will enter into a low-current (<5nA) power-down mode. When in this mode, the
transmitter will be completely off and cannot perform any function.
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 (anode toward the module). Either method
avoids damage to the module by preventing 5V from being placed on the PDN line while
allowing the line to be pulled low.
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 is poor. Note
that the values may need to be adjusted depending
on the noise present on the supply line.
Vcc IN
10μF
Figure 7: Supply Filter
TRANSMITTING DATA
Once a reliable 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 Series modules do not
incorporate internal encoding or decoding, a user has tremendous flexibility in
how data is handled.
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 range of manufacturers, including Linx.
They 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 units independently. These ICs are an excellent way to bring basic
remote control / status products to market quickly and inexpensively.
Additionally, it is a simple task to interface with inexpensive microprocessors,
such as the Microchip PIC, or one of many IR, remote control, or modem ICs.
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. While the LR Series is ideally suited to the long range transfer of
control and command information, it can also be used with great success for the
transfer of true variable data such as temperature, pressure, or sensor data.
However, the 260 - 470MHz band in which the module operates is regulated by
Part 15, Section 231 of the FCC regulations. Many types of transmissions,
especially those involving automatic transmissions or variable data, may need to
be periodic. You may wish to review Application Notes AN-00125 and AN-00140
along with Part 15, Section 231 of the FCC regulations for further details on
acceptable transmission content in the Unites States.
Another area of consideration is that of data structure or protocol. The data
should be formatted in a predictable way and should be able to deal with errors
due to interference. This will ensure that the data is received and interpreted
correctly. If you are not familiar with the considerations for sending serial data in
a wireless environment, you will want to review Application Note AN-00160.
Page 7
USING LADJ
The Level Adjust (LADJ) line allows the transmitter’s output power to be easily
adjusted for range control, lower power consumption, or to meet legal
requirements. This is done by placing a resistor between V
CC
and LADJ. The
value of the resistor determines the output power level. When LADJ is connected
to V
CC
, the output power and current consumption will be at its maximum. Figure
4 on Page 3 shows a graph of the output power vs. LADJ resistance.
This line is very useful during FCC testing to compensate for antenna gain or
other product-specific issues that may cause the output power to exceed legal
limits. A variable resistor can be temporarily used so that the test lab can
precisely adjust the output power to the maximum level allowed by law. The
variable resistor’s value can be noted and a fixed resistor substituted for final
testing. Even in designs where attenuation is not anticipated, it is a good idea to
place a resistor pad connected to LADJ and V
CC
so that it can be used if needed.
For more sophisticated designs, LADJ can be also controlled by a DAC or digital
potentiometer to allow precise and digitally variable output power control.
Page 6
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 8 shows a circuit using a Linx MS Series encoder. This chip works with
the Linx LICAL-DEC-MS001 decoder to provide simple remote control
capabilities. The decoder detects the transmission from the encoder, checks for
errors, and if everything is correct, replicates the encoder’s inputs on its outputs.
This makes registering key presses very simple.
100k
100k
100k
100k
100k
100k
1
DATA
GND
DATA IN
GND
PDN
VCC
GND
8
7
6
5
VCC
DATA
220
2
3
1
2
3
4
5
6
7
8
9
10
D6
D7
SEL_BAUD0
SEL_BAUD1
GND
GND
GND
TX_CNTL
DATA_OUT
MODE_IND
LICAL-ENC-MS001
D5
D4
D3
D2
VCC
VCC
D1
D0
SEND
CREATE_ADDR
20
19
18
17
16
15
14
13
12
11
100k
100k
100k
VCC
2.7k
4
IADJ/VCC RF OUT
TXM-xxx-LR
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 8: LR Transmitter and MS Encoder
Figure 9 shows a typical RS-232 circuit using the LR transmitter and a Maxim
MAX232 chip. The MAX232 converts RS-232 compliant signals from a PC to a
serial data stream, which is then transmitted by the LR module.
VCC
C1
4.7uF
C3
4.7uF
+
VCC
+ C2
4.7uF DB-9
1
6
GND
2
7
3
8
4
9
5
GND
GND
GND
C4
4.7uF
+
Figure 9: LR Transmitter and MAX232 IC
Figure 10 shows an example of using the LR transmitter with a Linx QS Series
USB module. The USB module converts low-speed USB compliant signals from
a PC into a serial data stream, which is then transmitted by the LR module.
USB-B
GND
DAT+
DAT -
5V
4
3
2
1
GSHD
GSHD
GND
6
5
GND GND
Figure 10: LR Transmitter and Linx QS Series USB Module
Page 9
+
C5
4.7uF
+
MAX232
1
2
3
4
5
6
7
8
C1+
V+
C1-
C2+
C2-
V-
T2OUT
R2IN
VCC
GND
T1OUT
R1IN
R1OUT
T1IN
T2IN
R2OUT
16
15
14
13
12
11
10
9
TXM-xxx-LR
GND
1
2
GND
VCC
3
4
GND
DATA
GND
PDN
VCC
GND
8
7
6
5
VCC
GND
LADJ/VCC ANT
750
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
DCD
DSR
DATA_IN
DATA_OUT
RTS
CTS
DTR
16
15
14
GND
13
12
11
10 VCC GND
9
TXM-xxx-LR
1
2
3
4
GND
DATA
GND
PDN
VCC
GND
8
7
6
5
VCC
GND
750
LADJ/VCC ANT
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