TXE-315-KH2
TXE-418-KH2
TXE-433-KH2
WIRELESS MADE SIMPLE
®
KH2 SERIES TRANSMITTER / ENCODER DATA GUIDE
DESCRIPTION
The KH2 Series is ideally suited for volume use
in OEM applications such as remote control and
command, and keyless entry. Housed in a
compact SMD package, it combines a highly-
optimized RF transmitter with an on-board
encoder. When paired with a matching KH2
Series receiver / decoder module, a reliable
wireless link is formed, capable of transferring
the status of 8 parallel inputs over distances of
up to 3,000 feet. Ten tri-state address lines
provide 59,049 (3
10
) addresses for security and
uniqueness. No external RF components are
required except an antenna, making integration
straightforward.
1.220"
0.630"
RF TRANSMITTER/ENCODER
TXE-418-KH2
LOT 10000
0.180"
Figure 1: Package Dimensions
FEATURES
n
n
n
n
Low cost
On-board encoder
8 parallel binary inputs
3
10
addresses for security and
uniqueness
n
No external RF components
required
n
n
n
n
n
n
Ultra-low power consumption
Compact SMD package
Stable SAW-based architecture
Adjustable output power
Transmit enable line
No production tuning
APPLICATIONS INCLUDE
n
n
n
n
n
n
n
n
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Remote Control / Command
Keyless Entry
Garage / Gate Openers
Lighting Control
Call Systems
Home / Industrial Automation
Fire / Security Alarms
Remote Status Monitoring
Wire Elimination
ORDERING INFORMATION
PART #
DESCRIPTION
TXE-315-KH2
Transmitter 315MHz
TXE-418-KH2
Transmitter 418MHz
TXE-433-KH2
Transmitter 433MHz
RXD-315-KH2
Receiver 315MHz
RXD-418-KH2
Receiver 418MHz
RXD-433-KH2
Receiver 433MHz
EVAL-***-KH2
Basic Evaluation Kit
*** = 315, 418 (Standard), 433.92MHz.
Transmitters are supplied in tubes of 20 pcs.
Revised 9/27/11
ELECTRICAL SPECIFICATIONS
Parameter
POWER SUPPLY
Operating Voltage
Supply Current
Power-Down Current
TRANSMITTER SECTION
Transmit Frequency Range:
TXE-315-KH2
TXE-418-KH2
TXE-433-KH2
Center Frequency Accuracy
Output Power
Harmonic Emissions
ANTENNA PORT
RF Output Impedance
ENCODER SECTION
Data Length
Average Data Duty Cycle
Encoder Oscillator
Data Input:
Logic Low
Logic High
Input Sink Current
ENVIRONMENTAL
Operating Temperature Range
–
-30
–
+70
–
–
–
F
ENC
–
–
–
–
0.0
V
CC
x 0.8
0.6
26 bits 3x
50%
70
–
–
1.0
–
–
–
0.2 x V
CC
V
CC
1.2
–
–
kHz
VDC
VDC
mA
–
4
4
4
4
4
R
OUT
–
50
–
Ω
4
–
P
O
P
H
F
C
–
–
–
-75
-4
–
315
418
433.92
–
+2
–
–
–
–
+75
+4
-36
MHz
MHz
MHz
kHz
dBm
dBc
–
–
–
–
2,3
2
V
CC
I
CC
I
PDN
2.7
–
–
–
1.5
1.0
5.2
–
–
VDC
mA
µA
–
1,4
–
Designation
Min.
Typical
Max.
Units
Notes
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
CC
Any Input or Output Pin
Operating Temperature
Storage Temperature
Soldering Temperature
-0.3
-0.3
-30
-45
+225°C
to
+6.0
to
V
CC
to
+70
to
+85
for 10 seconds
VDC
VDC
°C
°C
*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.
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
1
2
3VDC
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
LADJ/GND ANT
D0
GND
D1
A9
GND
A8
VCC
A7
TE
A6
D2
A5
D3
A4
D4
A3
D5
A2
D6
A1
D7
A0
Figure 2: Test / Basic Application Circuit
TYPICAL PERFORMANCE GRAPHS
°
C
4
12
11
10
9
8
7
6
5
4
3
2
1
0
2.5
+8
+7
+6
+5
+4
+3
+2
+1
0
-1
-2
-3
-4
-5
-6
-7
Table 1: KH2 Series Transmitter Electrical Specifications
Notes
1.
2.
3.
4.
Current draw with 50% mark / space ratio.
Into a 50Ω load.
With 430Ω resistor on LADJ.
Characterized, but not tested.
With LADJ tied to ground
Output Power Into 50 ohms (dBm)
With LADJ tied to ground
Supply Current (mA)
With 430Ω resistor on LADJ
With 430Ω resistor on LADJ
4.0
4.5
3.0
3.5
Supply Voltage (V)
5.0
2.5
4.0
4.5
3.0
3.5
Supply Voltage (V)
5.0
Figure 3: Supply Current vs. Supply Voltage
Figure 4: Output Power vs. Supply Voltage
*CAUTION*
Output Power (dBm)
+8
+7
+6
+5
+4
+3
+2
+1
0
-1
-2
-3
-4
51 100 150 200 240 300 360 430 510 560 620 680 750 820
910
1.1K
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.
5V
3V
LADJ Pin Resistor Value (Ω)
Figure 5: Output Power vs. LADJ Resistor
Page 2
Page 3
PIN ASSIGNMENTS
1
2
3
4
5
6
7
8
9
10
11
12
LADJ/GND ANT
D0
GND
D1
A9
GND
A8
VCC
A7
TE
A6
D2
A5
D3
A4
A3
D4
A2
D5
D6
A1
D7
A0
24
23
22
21
20
19
18
17
16
15
14
13
MODULE DESCRIPTION
The KH2 Series transmitter / encoder module combines a high-performance
Surface Acoustic Wave (SAW) based transmitter with an on-board encoder.
When combined with a Linx KH2 Series receiver / decoder, a highly reliable RF
link capable of transferring control or command data over line-of-sight distances
of up to 3,000 feet is formed. The module accepts up to 8 parallel inputs, such
as switches or contact closures, and provides ten tri-state address lines for
security and creation of 59,049 (3
10
) unique transmitter / receiver relationships.
The KH’s compact surface-mount package integrates easily into existing designs
and is friendly to hand production or automated assembly.
Address Inputs
A0-A9
SAW
Oscillator
TX Enable
Divider
Sync
Counter
OSC
GATE
Parallel
Inputs
D0-D7
Figure 6: KH2 Series Transmitter Pinout (Top View)
50Ω RF OUT
(ANT)
Keyed Output
Buffer
PIN DESCRIPTIONS
Pin #
1
TRI-Detect
Name
Description
Output Isolation
& Filter
RF Amplifier
Level Adjust. This line can be used to adjust the output
power level of the transmitter. Connecting to GND will give
GND / LADJ
the highest output, while placing a resistor to GND will
lower the output level.
Data Input Lines. When TE goes high, the module will
encode the state of these lines for transmission. Upon
receipt of a valid transmission, the receiver / decoder will
replicate these lines on its output lines.
Analog Ground
Supply Voltage
Transmit Enable Line. When this line goes high, the
module will encode the states of the address and data lines
into a packet and transmit the packet three times.
Address Lines. The state of these lines must match the
state of the receiver’s address lines in order for a
transmission to be accepted.
Analog Ground
50-ohm RF Output
RF STAGE
THEORY OF OPERATION
ENCODER STAGE
Figure 7: KH2 Series Transmitter Block Diagram
2, 3,
7-12
4
5
D0 - D1
GND
V
CC
The KH2 Series transmitter operation is straightforward. When the Transmit
Enable (TE) line is taken high, the on-board encoder IC is activated. The encoder
detects the logic states of the data and address lines. These states are formatted
into a 3-word transmission, which continues until the TE line is taken low. The
encoder creates a serial data packet that is used to modulate the transmitter.
The transmitter section is based on a simple, but highly-optimized, architecture
that achieves a high fundamental output power with low harmonic content. This
ensures that most approval standards can be met without external filter
components. The KH2 Series transmitter is exceptionally stable over variations
in time, temperature, and physical shock as a result of the precision SAW device
that is incorporated as the frequency reference.
The transmitted signal may be received by a Linx KH2 Series receiver / decoder
module or a Linx LR Series receiver combined with the appropriate decoder IC.
Once data is received, it is decoded using a decoder IC or custom
microcontroller. The transmitted address bits are checked against the address
settings of the receiving device. If a match is confirmed, the decoder’s outputs
are set to replicate the transmitter’s inputs.
6
TE
13-22
A0-A9
23
24
GND
ANT
Page 4
Page 5
ENCODER OPERATION
The KH2 Series transmitter internally utilizes
the HT640 encoder from Holtek. The
encoder begins a three-word transmission
cycle when the Transmission Enable line
(TE) is pulled high. This cycle will repeat
itself for as long as the TE line is held high.
Once TE falls low, the encoder output
completes its final cycle and then stops as
shown in the Encoder / Decoder Timing
diagram. When a transmission enable signal
is applied, the encoder scans and transmits
the status of the 10 bits of the address code
and the 8 bits of the data serially in the order
A0 to A9, D0 to D7.
Power On
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 power supply for the
module should be a high priority during design.
Vcc TO
MODULE
10Ω
Vcc IN
+
Standby Mode
10μF
No
Transmission
Enabled?
Yes
3 Data Words
Transmitted
A 10Ω resistor in series with the supply followed by a
Figure 10: Supply Filter
10µF tantalum capacitor from V
CC
to ground will help in cases where the quality
of supply power is poor. These values may need to be adjusted depending on
the noise present on the supply line.
DATA INPUTS
When the Transmit Enable (TE) line goes high, the states of the eight data input
lines are recorded and encoded for transmission. The data lines are tri-state,
which means that they can be high, low, or floating, though the decoder will
interpret the floating state as a low. This feature means that the data lines do not
require pull-up or pull-down resistors. The states of the data lines can be set by
switches, jumpers, microcontrollers, or hardwired on the PCB.
The encoder will send the states of the address and data lines three times. If the
TE line is still high, it will begin the cycle again. This means that the states of the
data lines are refreshed with each cycle, so the data lines can be changed
without having to pull TE low. There can be up to a 150mS lag in response as
the transmitter finishes one cycle then refreshes and starts over.
Transmission
The status of each address / data pin can be
Still Enabled?
individually preset to logic high, low, or
floating. The floating state on the data input
is interpreted as logic low by the decoders
3 Data Words
Transmitted
since the decoder output only has two
Continuously
states. The address pins are usually set to
transmit particular security codes by DIP
switches or PCB wiring, while the data is
Figure 8: Encoder Flowchart
selected using push buttons or electronic
switches. The floating state allows the KH2 transmitter to be used without pull-
up or pull-down resistors on the data and address input lines.
Encoder
Transmit
Enable
Encoder
Data Out
ENABLING TRANSMISSION
< 1 Word
3 Words
2 Words
Check
Transmitted Continuously
214 Clocks
3 Words
214 Clocks
Decoder VT
Decoder
Data Out
The module’s Transmit Enable (TE) line controls transmission status. When
taken high, the module initiates transmission, which continues until the line is
pulled low or power to the module is removed. In some cases this line will be
wired permanently to V
CC
and transmission controlled by switching V
CC
to the
module. This is particularly useful in applications where the module powers up
and sends a transmission only when a button is pressed on the remote.
Check
USING LADJ
1/2 Clock Time
1/2 Clock Time
Figure 9: Encoder / Decoder Timing Diagram
SETTING THE TRANSMITTER ADDRESS
The module provides ten tri-state address lines. This allows for the formation of
up to 59,049 (3
10
) unique transmitter-receiver relationships. Tri-state means that
the address lines have three distinct states: high, low, or floating. These pins
may be hardwired or configured via a microprocessor, DIP switch, or jumpers.
The receiver’s address line states must match the transmitter’s exactly for a
transmission to be recognized. If the transmitted address does not match the
receiver’s local address, then the receiver will take no action.
Page 6
The 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 GND and LADJ. When LADJ is connected
directly to GND, the output power will be at its maximum. Placing a resistor will
lower the output power by up to 7dB, as shown on Page 3 of this data guide.
This 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 used so that the test lab can precicely adjust the output
power to the maximun level allowed by law. The 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 GND so that it can be used if needed.
Page 7
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
Below is an example of a basic remote control transmitter utilizing the KH2
Series transmitter. When a key is pressed on the transmitter, a corresponding
line on the receiver goes high. A schematic for the receiver / decoder circuit may
be found in the KH2 Series Receiver Data Guide. These circuits are
implemented in the KH2 Series Basic Evaluation kit. They can be easily modified
for custom applications and clearly demonstrate the ease of using the KH2
Series modules for remote control applications.
VCC
VCC
SW0
R1
1
2
3
GND/LADJ
D0
D1
GND
VCC
TE
D2
D3
D4
D5
D6
D7
TXE-xxx-KH2
ANT
GND
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
24
23
22
21
20
19
18
17
SW-DIP-10
16
15
14
13
GND
GND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
SW-SPDT
GND
0 OHM
VCC
SW1
VCC
GND
4
5
6
7
8
9
10
11
12
SW-SPDT
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
R2
100K
VCC
VCC
+ C1
10uF
CR2032
3V
LITHIUM
GND
GND
GND
Figure 11: Basic Remote Control Transmitter
The ten-position DIP switch is used to set the address to either ground or
floating. Since the floating state is a valid state, no pull-up resistors are needed.
The data lines are pulled high by momentary pushbuttons. Since the floating
state is interpreted as a low by the decoder, no pull-down resistors are needed.
Diodes are used to pull the TE line high when any data line goes high, while
isolating the data lines from each other. This will make the transmitter send data
when any button is pressed without affecting any of the other data lines.
The KH2 Series transmitter / encoder module is also suitable for use with the
Linx OEM function receivers. These receivers are FCC certified, making product
introduction extremely quick. Information on these products can be found on the
Linx website at www.linxtechnologies.com.
Page 9
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