RXM-869-ES_ Linx Technologies Inc, RXM-869-ES_ Datasheet - Page 4

• Manufacturer Part Number: RXM-869-ES_
• Description: RECEIVER RF 869MHZ 16PIN SMD
• Manufacturer: Linx Technologies Inc
• Series: -r

Specifications of RXM-869-ES_

• Frequency: 869MHz
• Sensitivity: -102dBm
• Data Rate - Maximum: 56 kbps
• Modulation Or Protocol: FM, FSK
• Current - Receiving: 6.5mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 16-SMD
• Board Size: 20.6 mm x 16 mm x 3.2 mm
• Minimum Operating Temperature: 0 C
• Supply Voltage (min): 4.5 V
• Product: RF Modules
• Maximum Frequency: 869.85 MHz
• Supply Voltage (max): 5.5 V
• Maximum Operating Temperature: + 70 C
• Applications: -
• Memory Size: -
• Features: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Applications: -
• Memory Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: RXM-869-ES; RXM-869-ES

USING THE PDN PIN
USING THE RSSI PIN
POWER SUPPLY REQUIREMENTS
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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
(<50µA) 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
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.
The receiver’s Received Signal Strength Indicator (RSSI) line serves a variety of
uses. The RSSI line has a dynamic range of 60dB (typical) and outputs a voltage
proportional to the incoming signal strength. A graph of the RSSI line’s
characteristics appears in the Typical Performance Graphs section. It should be
realized that the RSSI levels and dynamic range will vary slightly from part to
part. It is also important to remember that the RSSI output indicates the strength
of any in-band RF energy and not necessarily just that from the intended
transmitter; therefore, it should only be used to qualify the level and presence of
a signal.
The RSSI output can be used to create external squelch circuits. It can be
utilized during testing or even as a product feature to assess interference and
channel quality by looking at the voltage level with all intended transmitters 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.
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.
A 10Ω resistor in series with the supply followed by a
10µF tantalum capacitor from V
of the supply is poor. Note that the values may need to be adjusted depending
on the noise present on the supply line.
CC
to ground will help in cases where the quality
CC
Figure 9: Supply Filter
Vcc IN
.
10Ω
Vcc TO
MODULE
+
10μF
PROTOCOL GUIDELINES
INTERFERENCE CONSIDERATIONS
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.
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.
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