Linx HP-3 series Guide

HP SERIES-3 TRANSMITTER DESIGN GUIDE
DE S C R IP TION:
The HP -3 R F transmitter module is the third generation of the popular HP series and
offers complete compatibility and numerous enhancements over previous
generations. Like its predecessors, the HP -3 is designed for the cost-effective, high-
performance wireless transfer of analog or digital information in the popular
902-928MHz band. All HP -3 series parts continue to feature eight parallel selectable
channels, but versions are also available which add serial selection of 100 channels.
To ensure reliable performance, the transmitter employs F M/FS K modulation and a
microprocessor-controlled synthesized architecture. The transmitter is pin- and
footprint-compatible with all previous generations but its overall physical s ize has
been reduced. B oth S MD and pinned packages are now available. When paired with
an HP -3 receiver, a reliable link is created for trans ferring analog and digital
information up to 1000 ft. (under optimal conditions). Like all Linx modules, the
HP -3 requires no tuning or additional R F components (except an antenna), making
integration s traightforward, even for engineers without prior R F experience.
H IGH -P ERFORMANCE
RF MODULE
TXM-900-HP3
R evised 7/2/03
FEATURES:
€ 8parallel, 100 s erial (P S Vers ions)
User-S electable C hannels
€P recis ion F requency S ynthes ized
Architecture
€F M/F S K Modulation F or Outstanding
P erformance and Noise Immunity
€ Transparent Analog/Digital Interface
€High Data R ate (up to 56k)
€Wide-R ange Analog C apability Including
Audio (50Hz-28kHz)
€P ower-Down and C T S F unctions
€C ost-E ffective
€P inned or S MD P ackaging
€Wide S upply R ange (2.8-13V DC )
€E xtended Temperature R ange
(-30°C to +85°C )
€No P roduction Tuning or E xternal R F
C omponents R equired (E xcept Antenna)
€C ompatible With P revious HP S eries
Modules
P A R T # DE S C R IP T ION
T XM-900-HP 3-P P O HP -3 Trans mitter (P INNE D 8 C H only)
T XM-900-HP 3-P P S HP -3 Trans mitter (P INNE D 8p /100s C H)
T XM-900-HP 3-S P O HP -3 Trans mitter (S MD 8 C H only)
T XM-900-HP 3-S P S HP -3 Trans mitter (S MD 8p /100s C H)
MDE V-900-HP 3-P P S Development K it 900MHz (P inned P kg.)
MDE V-900-HP 3-S P S Development K it 900MHz (S MD P kg.)
ORDERING INFORMATION
APPLICATIONS INCLUDE:
€G eneral W ire E limination
€Wireles s Data Trans fer
€Wireles s Analog / Audio
€Home / Industrial Automation
€Wireles s Networks
€R emote C ontrol
€R emote Access
€R emote Monitoring / Telemetry
€Alarm / S ecurity S ystems
€Long-R ange R F ID
€ MIDI Links
€ Voice/Music / Intercom Links

Figure 1: Performance Data Table
Page 2
1. Over entire operating voltage range
2. PDN pin low
3. Serial Mode
4. 100 Serial channels on PS versions only
5. Does not change over 3-13 VDC supply
6. Into 50 Ohms
7. Receiver will not reliably hold a DC level. See RX manual for minimum transition rate.
8. Voltage specified is modulation pin voltage
9. See page 15.
Notes:
TRANSMITTER SPECIFICATIONS
ABOUT THESE MEASUREMENTS
The performance parameters listed below are based on module operation at
25°C from a 5V DC supply unless otherwise noted.
Parameter Designation Min. Typical Max. Units Notes
POWER SUPPLY
Input Voltage VCC 2.8 – 13.0 VDC –
Supply Current ICC –1417mA1
Power-Down Current IPDN ––15
µ A2
TRANSMIT SECTION
Transmit Frequency Range FC902.62 – 927.62 MHz 3
Center Frequency Accuracy -50 +50 kHz –
Available Channels 8 (Par.) – 100 (Ser.) 4
Channel Spacing – 250 – kHz –
Occupied Bandwidth – 115 140 kHz –
Output Power -3 0 +3 dBm 5
Spurious Emissions – -45 – dBm 6
Harmonic Emissions – -60 -47 dBm 6
Data Bandwidth 100 – 56,000 bps 7
Analog/Audio Bandwidth 50 – 28,000 Hz 7
Data input:
Logic low GND – 0.5 VDC –
Logic high 2.8 – 5.2 VDC –
Data Input Impedance – 200 – kOhms –
Frequency Deviation @ 3VDC 60 70 110 kHz 8
Frequency Deviation @ 5VDC 90 115 140 kHz 8
ANTENNA PORT
RF input impedance RIN –50–Ohms –
TIMING
Transmitter Turn-on Time T1–710mSec 9
Max Channel-Change Time T2–11.5mSec 9
ENVIRONMENTAL
Operational Temperature -30 +85 °C –

Page 3
Figure 2: Maximum Ratings Table
Absolute Maximum Ratings:
Supply voltage Vcc, using pin 7 -0.3 to +18 VDC
Operating temperature -30°C to +85°C
Storage temperature -45°C to +85°C
Soldering temperature +260°C for 10 sec.
Any input or output pin -0.3 to Vcc
*NOTE* Exceeding any of the limits of this section may lead to permanent
damage of the device. Furthermore, extended operation at these maximum
ratings may reduce the life or affect the function of this device.
*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.
Figure 5: TX Powerup to Valid RX Analog
Figure 3: Power-Up To CTS
TYPICAL PERFORMANCE GRAPHS
Figure 8: Square-Wave Modulation
Linearity
Figure 6: Sine-Wave Modulation Linearity
Figure 4: TX Powerup to Valid RX Data
Figure 7: Triangle-Wave Modulation
Linearity
IN
OUT
IN
TX VCC/PDN High
TX VCC/PDN High
RX Data
Demodulated Analog Data
(RX)
TX CTS
TX VCC/PDN High
OUT
IN
OUT

PIN Name Equivalent CTK Description
PIN #
Ground
50 Ohm RF Output
Channel Select 0
CS0
Channel Select 1/Serial Select Clock
CS1
Channel Select 2 /Serial Select Data
Clear-to-Send
Output
Ground/Mode
Voltage Input 2.8-16V
Power Down
(Active Low)
Digital/Analog Input
See text "Inputting Digital Data"
CS2
Mode
CTS
Out
GND
RF/ANT Out
CS0
CS1/SS CLOCK
CS2/SS DATA
PDN
CTS
GND/MODE
Analog In/Data In
VCC
1
3
13
20
2
5
6
7
9
8
11
12
4
14-19
21-24
10
1
2
3
4
5
7
6
9
10
8
25K
25K
25K
100K 160K
510K 20pF
50
RF
Out
PDN
430K
VIN
SMD Pinned
N/C SMD (Only) No Connection
25K
Page 4
PIN DESCRIPTION
Figure 9: Pin Functions and Equivalent Circuits

Page 5
The transmitter is available in two package styles. The pinned SIP style is
designed for through-hole application and has 10 pins spaced at 0.1" intervals.
Pin 1 is on the far left of the board when viewed from the front. The package may
be inserted at right angles or bent to lie down (with the cover facing up) on the
PCB. Avoid repeated bending of the pins as they may weaken and break.
The surface-mount version is housed in a 24 pad hybrid SMD package which
has been designed to facilitate both hand and automated assembly. Pin one is
on the lower left when viewed as shown above. Castellation grooves have been
provided for ease of hand soldering and inspection.
PHYSICAL PACKAGING
RECOMMENDED PAD LAYOUT
The following drawings illustrate the recommended circuit-board footprints for
the HP-3 series transmitter modules. Be sure to also review the physical layout
and the antenna recommendations contained elsewhere in this guide.
0.628"
0.070"
0.100"
0.060"
.060"
.3"
.10"
.060"
.030" Dia. Finished
Figure 11: Suggested PCB Footprint
Surface-Mount TransmitterPinned Transmitter
Figure 10: Transmitter Physical Package
ENCAPSULATION NOTICE
In some applications the designer may wish to encapsulate the product's circuit
board. Among the common reasons for doing so are environmental protection
and security. The dielectric constant of encapsulation and potting materials
varies and can adversely affect transmitter performance. For this reason, Linx
does not recommend the encapsulation of our products. Doing so will void all
product warranties. It should be noted, however, that customers have reported
success with a variety of encapsulation materials and techniques. Should you
choose to encapsulate your product, careful testing should be conducted to
determine the suitability of the chosen material.
0.178"
1.290"
0.680"
LOT 10000
1
HP SERIES RF TRANSMITTER
TXM-900-HP3-PP*
0.125"
0.628"
1.260"
LOT 10000
1
HP SERIES RF TRANSMITTER
TXM-900-HP3-SP*

Page 6
PRODUCTION GUIDELINES
Pinned Transmitter Hand Assembly
The SIP module pins may be hand or wave-soldered. The module should not be
subjected to reflow. Linx recommends wash-free manufacturing techniques. The
modules are wash-resistant, but are not hermetically sealed. If a wash is used,
a drying time, sufficient to allow the evaporation of any moisture which may have
migrated into the module, must be allowed prior to applying electrical power. If
the wash contains contaminants, transmitter performance may be adversely
affected even after drying.
SMD Transmitter Hand Assembly
The SMD version is housed in a hybrid
SMD package which has been designed
to support hand or automated reflow
techniques. The package’s primary
mounting surface is the pads located on
the bottom of the module. Since these
pads are inaccessible during mounting,
plated castellations run up the sides of the
module to facilitate solder wicking. This
allows for very quick and efficient hand
soldering for prototyping and small
volume production.
If the recommended pad placement has been followed, the pad on the board will
extend slightly past the edge of the module. Touch both the PCB pad and the
module castellation with a fine soldering tip. Tack one module corner first, then
work around the remaining attachment points being careful not to exceed the
solder times listed below.
Care should be taken, especially when hand-soldering, not to use excessive
amounts of flux as it will wick under the module and potentially impair its function.
In many cases, no-clean solder is the best choice. The modules are wash-
resistant, but are not hermetically sealed. Linx recommends wash-free
manufacturing techniques. If a wash is used, a drying time, sufficient to allow any
moisture which may have migrated into the module to evaporate, must be
allowed prior to applying electrical power. If the wash contains contaminants,
transmitter performance may be adversely affected even after drying.
Castellations
PCB Pads
Soldering Iron
Tip
Solder
Figure 12: Soldering Technique
Absolute Maximum Solder Times
Hand-Solder Temp. TX +225°C for 10 Sec.
Hand-Solder Temp. RX +225°C for 10 Sec.
Recommended Solder Melting Point +180°C
Reflow Oven: +220° Max. (See adjoining diagram)

Page 7
SMD TRANSMITTER AUTOMATED ASSEMBLY GUIDELINES
For high-volume assembly, most users will want to auto-place the modules. SMD
versions of the modules have been designed to maintain compatibility with most
pick-and-place equipment, however, due to the module's hybrid nature certain
aspects of the automated assembly process are far more critical than for other
component types.
Following are brief discussions of the three primary areas where caution must be
observed.
Reflow Temperature Profile
The single most critical stage in the automated assembly process is the reflow
process. The reflow profile below should not be exceeded since excessive
temperatures or transport times during reflow will irreparably damage the
modules. Assembly personnel will need to pay careful attention to the oven's
profile to ensure that it meets the requirements necessary to successfully reflow
all components while remaining within the limits mandated by the modules
themselves.
Shock During Reflow Transport
Since some internal module components may reflow along with the components
placed on the board being assembled, it is imperative that the module not be
subjected to shock or vibration during the time solder is liquidus.
Washability
The modules are wash-resistant, but are not hermetically sealed. Linx
recommends wash-free manufacturing techniques, however, the modules can
be subjected to a wash cycle provided that a drying time is allowed prior to
applying electrical power to the parts. The drying time should be sufficient to
allow any moisture which may have migrated into the module to evaporate, thus
eliminating the potential for shorting damage during power-up or testing. If the
wash cycle contains contaminants, transmitter performance may be adversely
affected, even after drying.
Figure 13: Maximum Reflow Profile
125°C
600
0
50
100
150
200
250
300
°C
120 180 240 300
30 90 150 210 270 330 360
180°C
210°C
220°C
Temperature
Time (Seconds)
Ideal Curve
Limit Curve
Forced Air Reflow Profile
1-1.5 Minutes
2-2.3 Minutes
Ramp-up
Preheat Zone
Cooling
Soak Zone
Reflow Zone
20-40 Sec.
2 Minutes Max.

Page 8
Amplifier
VCO RF Out
Band Pass
Filter
28kHz Low Pass
Filter
Data
In
PLL
4MHz
Int. Osc.
MODE
CS0
CS1
CS2
12MHz
Crystal
Modulator
Figure 14: HP-3 Series Transmitter Block Diagram
THEORY OF OPERATION
The TXM-HP3 is a high-performance, multi-channel RF transmitter capable of
transmitting both analog (FM) and digital (FSK) information. FM/FSK modulation
offers significant advantages over AM or OOK modulation methods including
increased noise immunity and the receiver's ability to "capture" in the presence of
multiple signals. This is especially helpful in crowded bands like those in which the
HP-3 operates.
Let's take a brief look at each transmitter section. A precision 12.00MHz Voltage-
Controlled Crystal Oscillator (VCXO) serves as the frequency reference for the
transmitter. Incoming signals are filtered to limit their bandwidth and then used to
directly modulate this reference. Direct reference modulation inside the loop
bandwidth allows a fast startup while allowing a wide modulation bandwidth and
near DC modulation capability. This results in accurate reproduction of analog
and digital content and eliminates the need for code balancing.
The modulated 12.00MHz reference frequency is applied to the Phase-Locked
Loop (PLL). The PLL, combined with a 902-928MHz VCO, forms a stable
frequency synthesizer that can be programmed to oscillate at the desired
transmit frequency. An on-board micro-controller manages the PLL programming
functions and greatly simplifies user interface. The micro-controller reads the
channel-selection lines and programs the on-board synthesizer. This frees the
designer from complex programming requirements and allows for manual or
software channel selection. The micro-controller also monitors the status of the
PLL and indicates when the transmitter is stable and ready to transmit data by
raising the CTS line high.
The PLL locked carrier is amplified and buffered to isolate the VCO from the
antenna and to increase the output power of the transmitter. The output of the
buffer amplifier is connected to a filter network which suppresses harmonic
emissions. Finally, the signal reaches the single-ended antenna port, which is
matched to 50 ohms to support commonly available antennas, such as those
manufactured by Linx.

BOARD LAYOUT GUIDELINES
If you are familiar with RF you may be concerned about specialized layout
requirements. Fortunately, by carefully adhering to a few basic design and
layout rules transmitter integration is generally very straightforward.
Page 5 shows the suggested PCB footprint
for the HP-3 transmitter. A groundplane (as
large as possible) should be placed on a
lower layer of your PC board opposite the
transmitter. This groundplane can also be
critical to the performance of your antenna
which will be discussed later in the
manual.
The transmitter should be kept away from other components on your PCB,
especially high-frequency noise sources such as an oscillator or switching supply.
To mount a pinned version of the transmitter parallel to the PC board, bend it
over so that the plastic cover faces away from the board.
Do not route PCB traces directly under SMD packaged versions. The underside
of the module has numerous signal-bearing traces and vias which could short or
couple to traces on the product's circuit board.
The trace from the transmitter to the antenna should be kept as short as
possible. For runs greater than 1/4 inch use 50-ohm coax or a 50-ohm microstrip
transmission line as shown below. Handy software for calculating microstrip
lines is available on the Linx website (www.linxtechnologies.com).
The typical output power of the HP-3 transmitter is
right at Part-15 limits. Sometimes, it is necessary
to slightly attenuate the output to compensate for
antenna gain. This is accomplished using a three-
resistor attenuation network as shown. While this
network is often referred to as a “T” pad the actual
resistor orientation is usually not critical. Use only
surface-mount type resistors grouped closely. The
series pads may be bridged if the network is not needed. Further details can be
found in application note #00150 - "Use and Design of T-Attenuation Pads".
Page 9
Full groundplane on inner or lower board layer
Microstrip
Figure 15: Groundplane Treatment
Figure 16: Microstrip Formulas (Er = Dielectric constant of pc board material)
TYPICAL LAYOUT
MICROSTRIPS
GROUND
RF IN
ANT.
R1R1
R2
GROUNDPLANE
ON LOWER LAYER
Figure 17: T-pad Layout
Effective
Dielectric Width/Height Dielectric Characteristic
Constant (W/d) Constant Impedance
4.8 1.8 3.59 50.0
423.07 51.0
2.55 3 2.12 48.0

POWER SUPPLY GUIDELINES
The user must provide a clean source of
power to the transmitter to ensure proper
operation. The HP-3 incorporates a precision
low-dropout regulator on-board which allows
operation over an input voltage range of 2.8 to
13 VDC. Figure 18 shows a typical supply
filter. This filter should be placed close to the
module's supply lines. Its actual values will
depend on the type and frequency of noise
present in the user's product.
The HP-3 can be put into an ultra-low-current (<15µA) power-down mode by
holding the PDN pin low. If the PDN pin is left open or held high, the transmitter
will turn on. In power-down mode, the transmitter is completely shut down.
Page 10
POWER-UP SEQUENCE
The HP-3 transmitter is controlled
by an on-board microprocessor.
When power is applied, a start-up
sequence is executed. At the end
of the start-up sequence, the
transmitter is ready to transmit data.
Figure 19 shows the start-up
sequence. This sequence is
executed when power is applied to
the VCC pin or when the PDN pin is
cycled from low to high.
On power-up, the on-board micro-
processor reads the external
channel-selection lines (parallel
mode) or serial channel input (serial
mode) and sets the frequency
synthesizer to the appropriate
channel. Figure 3 on page 3 shows
the typical turn-on response time for
an HP-3 transmitter. When the
frequency synthesizer has locked
on to the proper channel frequency, the circuit is ready to accept data. This is
acknowledged by the CTS line transitioning high. The module will then transmit
analog or digital data from the user's circuit.
The module can be put into an ultra-low-current (<15µA) power-down mode by
holding the PDN pin low. This removes all power from the transmitter's circuitry.
If PDN is left floating or held high, the transmitter will wake up and begin normal
operation. No transmitter functions work when PDN is low.
POWER ON
Determine Mode
Read Channel-
Selection Inputs Program Freq. Synth
To Default CH. 50
Program Frequency
Synthesizer
Crystal Oscillator
Begins to Operate
Crystal Oscillator
Begins to Work
Ready for
Serial Data Input
Program Frequency
Synthesizer
Determine State of
CTS Output Pin
Cycle Here Until More
Data Input, Mode Change
or PLL Loses Lock
Determine State of
CTS Output Pin
Cycle Here Until
Channel
or Mode Change
Serial ModeParallel Mode
Figure 18: Typical Supply Filter
Figure 19: Start-up Sequence
.1µF>22µF
Vcc IN
Vcc to
module