TXM-433-LR_ Linx Technologies Inc, TXM-433-LR_ Datasheet - Page 4

• Manufacturer Part Number: TXM-433-LR_
• Description: RF Modules & Development Tools RF Transmitter 433MHz
• Manufacturer: Linx Technologies Inc

Specifications of TXM-433-LR_

• Board Size: 12.7 mm x 9.1 mm x 3.3 mm
• Minimum Operating Temperature: - 40 C
• Supply Voltage (min): 2.1 V
• Product: RF Modules
• Maximum Frequency: 433.92 MHz
• Supply Voltage (max): 3.6 V
• Maximum Operating Temperature: + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

THE DATA INPUT
USING THE PDN PIN
USING LADJ
Page 6
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
to exceed the supply voltage, as permanent damage to the module could occur.
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
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
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.
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
value of the resistor determines the output power level. When LADJ is connected
to V
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
For more sophisticated designs, LADJ can be also controlled by a DAC or digital
potentiometer to allow precise and digitally variable output power control.
CC
, the output power and current consumption will be at its maximum. Figure
CC
to turn on the transmitter. The pull-up should be a minimum
CC
). The DATA line should never be allowed
CC
so that it can be used if needed.
CC
. When used with a higher
CC
and LADJ. The
POWER SUPPLY REQUIREMENTS
TRANSMITTING DATA
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
power supply for the module should be a high priority
during design.
A 10Ω resistor in series with the supply followed by a
10µF tantalum capacitor from V
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.
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.
CC
to ground will help
Figure 7: Supply Filter
Vcc IN
10Ω
Vcc TO
MODULE
+
Page 7
10μF