Page 5
Page 4
PIN ASSIGNMENTS
GND
DATA
GND
GND
ANT
LADJ/VCC
PDN
VCC
1
2
3
4
5
6
7
8
Figure 5: LR Series Transmitter Pinout (Top View)
Pin #
Name
Description
1
GND
Analog Ground
2
DATA
Digital Data Input
3
GND
Analog Ground
4
LADJ/VCC
Level Adjust. This line can be used to adjust the output
power level of the transmitter. Connecting to VCC will give
the highest output, while placing a resistor to VCC will lower
the output level (see Figure 4 on Page 3).
5
ANT
50-ohm RF Output
6
GND
Analog Ground
7
VCC
Supply Voltage
8
PDN
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.
PIN DESCRIPTIONS
MODULE DESCRIPTION
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
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.
PLL
VCO
PA
XTAL
DATA
PDN
RF OUT
Figure 6: LR Series Transmitter Block Diagram
*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.