RXD-315-KH
RXD-418-KH
RXD-433-KH
WIRELESS MADE SIMPLE
KH SERIES RECEIVER/DECODER DATA GUIDE
DESCRIPTION
The KH Series is ideally suited for volume use in
OEM
applications
such
as
remote
control/command and keyless entry. It
combines an RF receiver with an on-board
decoder. When paired with a matching KH
Series transmitter/encoder module, a highly
reliable wireless link is formed, capable of
transferring the status of 8 parallel inputs along
for distances in excess of 300 feet. Ten tri-state
address lines provide 3
10
different addresses for
security and uniqueness. Housed in a compact
SMD package, the KH module utilizes a highly
optimized SAW architecture to achieve an
unmatched blend of performance, size,
efficiency, and cost. No external RF
components, except an antenna, are required,
making design integration straightforward.
1.430"
0.630"
RF RECEIVER/DECODER
RXD-418-KH
LOT 1000
0.18"
Figure 1: Package Dimensions
FEATURES
Low cost
On-board decoder
8 parallel binary outputs
3
10
addresses for security and
uniqueness
No external RF components
required
Ultra-low power consumption
Compact SMD package
Stable SAW-based architecture
Received data output
Transmission validation
No production tuning
APPLICATIONS INCLUDE
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
EVAL-***-KH
Basic Evaluation Kit
TXE-315-KH
Transmitter/Encoder 315 MHz
TXE-418-KH
Transmitter/Encoder 418 MHz
TXE-433-KH
Transmitter/Encoder 433 MHz
RXD-315-KH
Receiver/Decoder 315 MHz
RXD-418-KH
Receiver/Decoder 418 MHz
RXD-433-KH
Receiver/Decoder 433 MHz
*** Insert Frequency
Receivers are supplied in tubes of 20 pcs.
Revised 12/31/04
ELECTRICAL SPECIFICATIONS
Parameter
POWER SUPPLY
Operating Voltage
With Dropping Resistor
Supply Current
Power-down Current
RECEIVER SECTION
Receive Frequency
RXD-315-KH
RXD-418-KH
RXD-433-KH
Center Frequency Accuracy
IF
Noise Bandwidth
Data Rate
Data Output
Logic Low
Logic High
Receiver Sensitivity
ANTENNA PORT
RF Input Impedance
TIMING
Receiver Turn-On Time:
Via Vcc
DECODER
TX Data Length
Average Data Duty Cycle
Decoder Oscillator
Output Drive Current
ENVIRONMENTAL
Operating Temperature Range
–
-30
–
+70
–
–
FENC
–
–
–
–
0.6
26 bits 3x
50%
70
1
–
–
–
1.2
–
–
kHz
mA
–
–
–
6
–
5
7
10.5
mSec
5
RIN
–
50
–
FC
–
–
–
-75
–
–
100
0.0
VCC-0.3
-92
315
418
433.92
–
10.7
280
–
–
–
-102
–
–
–
+75
–
–
5,000
0.3
VCC
-106
MHz
MHz
MHz
kHz
MHz
kHz
bps
VDC
VDC
dBm
–
–
–
–
–
2
–
3
3,4
4
–
VCC
ICC
IPDN
2.7
4.7
5.0
–
3.0
5.0
7.0
700
4.2
5.2
8.0
950
VDC
VDC
mA
µA
–
1
–
–
Designation
Min.
Typical
Max.
Units
Notes
ABSOLUTE MAXIMUM RATINGS
Supply voltage VCC
Supply voltage VCC, using resistor
Any input or output Pin
RF input
Operating temperature
Storage temperature
Soldering temperature
-0.3
-0.3
-0.3
to
+4.2
to
+5.2
to
3.6
0
-30
to
+70
-45
to
+85
+225°C for 10 seconds
VDC
VDC
VDC
dBm
°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.
–
–
N3DB
–
VOL
VOH
–
PERFORMANCE DATA
These performance parameters are
based on module operation at 25°C
from a 3.0VDC supply unless
otherwise noted. Figure 2 at the right
illustrates
the
connections
necessary for testing and operation.
It is recommended all ground pins
be connected to the groundplane.
The pins marked NC have no
electrical connection and are
designed only to add physical
support.
5VDC
200
Ω
External
Resistor
3VDC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
NC
D0
D1
GND
VCC
PDN
D2
D3
D4
DATA
VT
D5
D6
D7
ANT
GND
NC
NC
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
28
27
26
25
24
23
22
21
20
19
18
17
16
15
Ω
Figure 2: Test/Basic Application Circuit
TYPICAL PERFORMANCE GRAPHS
10.0
6.0
5.0
4.0
3.0
2.5
2.0
1.5
1.0
0 0.18 0.5 0.9 1.25 1.94 2.53 3.10 4.80
Supply Current (mA)
°
C
–
16
12
8
4
0
2.7
3
3.5
4
Table 1: KH Series Receiver Electrical Specifications
Notes
1. *CRITICAL* In order to operate the device over this range it is necessary for a 200Ω resistor to be
placed in series with Vcc.
2. Potential rate of data recovered on the DATA line (pin 10). The decoder rate is internally fixed at about
2kbps.
3. When operating from a 5V source it is important to consider that the output will swing to well less than 5
volts as a result of the required dropping resistor. Please verify that the minimum voltage will meet the
high threshold requirement of the device to which data is being sent.
4. Vcc referenced to voltage on the Vcc pin, after dropping resistor
5. For a BER of 10-5 at 4800 baud. Sensitivity is affected by antenna SWR.
6. Time to valid data output.
7. Maximum drive capability of data outputs.
VSWR
Sensitivity Decrease (dB)
Supply Voltage (V)
Figure 3: Sensitivity vs. VSWR
Figure 4: Consumption vs. Supply Voltage
Data Out
Data Out
*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.
Page 2
Carrier
Carrier
Figure 6: Receiver Turn-off Time
Page 3
Figure 5: RF In vs. Receiver Response Time
PIN ASSIGNMENTS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
NC
D0
D1
GND
VCC
PDN
D2
D3
D4
DATA
VT
D5
D6
D7
ANT
GND
NC
NC
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
28
27
26
25
24
23
22
21
20
19
18
17
16
15
MODULE DESCRIPTION
The KH Series module combines the popular Linx LC Series receiver with a
decoder IC in a convenient SMD package. The module is ideal for general-
purpose remote control and command applications. When paired with a
matching Linx KH Series transmitter/encoder a highly reliable RF link capable of
transferring control and command over line-of-sight distances in excess of 300
feet (90m) is formed. The on-board receiver/decoder combination provides eight
switched outputs that correspond to the state of the data lines on the
transmitter’s encoder. Ten tri-state address lines are also provided to allow up to
59,049 unique identification codes.
50Ω RF IN
(Ant.)
Band Select
Filter
pre-
amplifier
10.7MHz
AM Detector
Limiting Amp Ceramic Filter
Data Slicer
Gilbert Cell
Mixer/Amp
RF Stage
10.7MHz
Bandpass Filter
DATA
Figure 7: KH Series Receiver Pinout (Top View)
PIN DESCRIPTIONS
Pin #
1
2, 3, 7, 8,
9, 12, 13,
14
4
5
Name
N/C
Description
No Connection. For physical support only.
SAW Local Oscillator
Decoder Stage
Oscillator
Divider
8-bit
Shift
Register
Latch
Circuit
AND
Circuit
D0
D1
D2
D3
D4
D5
D6
D7
D0 - D7
Data Output Lines. Upon a valid transmission these lines
will be set to replicate the state of the transmitter’s address
lines.
Analog Ground
Supply Voltage
Buffer
Data
Collector
Buffer
GND
VCC
Sync.
Detector
Comparator
Comparator
Control
Logic
10 Transmission Gate Circuit
6
PDN
Power Down. Pulling this line low will place the receiver into
a low-current state. The module will not be able to receive a
signal in this state.
Data output of the receiver prior to the encoder.
Valid Transmission. This line will go high when a valid
transmission is received.
Address Lines. The state of these lines must match the
state of the transmitter’s address lines in order for a
transmission to be accepted.
No Connection. For physical support only.
No Connection. For physical support only.
Analog Ground
50-ohm RF Input
A0 A1 A2 A3 A4 A5 A6 A7 A8 A9
Figure 8: KH Series Receiver Block Diagram
THEORY OF OPERATION
10
11
DATA
VT
The KH Series receiver module is designed to receive transmissions from a
matching KH Series transmitter module or other compatible Linx transmitter
product. When transmitted data is received, the data is presented to the on-
board decoder. If the incoming address data matches the local address settings,
the decoder's outputs are set to replicate the states of the transmitter’s data
lines.
The RF section of the KH module utilizes an advanced single-conversion
superhet design that incorporates a Surface Acoustic Wave (SAW) device, high
IF frequency and multi-layer ceramic filters. The SAW device provides a highly
accurate Local Oscillator (LO) frequency source with excellent immunity to
frequency shift due to age or temperature. The use of SAW devices in both the
KH transmitter and receiver modules allows the receiver’s pass opening to be
quite narrow, thus increasing sensitivity and reducing susceptibility to near-band
interference.
Page 5
15 - 24
A0 - A9
25
26
27
28
Page 4
N/C
N/C
GND
RF IN
DECODER OPERATION
The KH Series receiver internally utilizes the
HT658 decoder from Holtek. The decoders
receive data transmitted by the encoders and
interpret the first 10 bits of the code period as
address and the last 8 bits as data. A signal
on the DATA line then activates the oscillator,
which in turns decodes the incoming address
and data. The decoders will check the
received address twice continuously. If the
received address code matches the
decoder’s local address, the 8 bits of data are
replicated on the output lines, and the VT line
is set high to indicate the reception of a valid
transmission. That will last until the address
code is incorrect or no signal has been
received. The VT line is high only when the
transmission is valid, otherwise it is low
always. The output type is momentary. The
data outputs follow the encoder during a valid
transmission and then reset.
Power On
THE DATA OUTPUTS
When data is received and the incoming address data matches with the local
address settings, the module’s eight data output lines are set to replicate the
state of the transmitter’s data lines. In addition, the valid transmission line (VT,
pin 11) will go high to indicate reception and decoding of the data. The data lines
have a low sink and source capability so external buffering is generally required
if loads are to be driven directly.
In addition to the decoded data outputs, raw data is also available via a CMOS-
compatible data output (DATA, pin 10). The output of this pad is the actual
received data stream from the receiver and is always active regardless of
address line status. It is made available for troubleshooting or monitoring internal
data flow. It can also be used in mixed mode systems where data may come
from another source in addition to a KH Series transmitter module. This data can
then be channeled to an external processor for decoding.
Standby Mode
Disable VT &
Ignore the Rest of
This Word
No
Code In?
Yes
Address Bits
Matched?
Yes
Store Data
No
Match
Previous Stored
Data?
No
Yes
No
2 Times
of Checking
Completed?
RECEIVING DATA
Although the internal decoder handles all of the decoding and output for
transmissions from a KH Series transmitter or an OEM transmitter, the KH series
receiver will output the raw received data on the DATA line. This allows the
designer to create a mixed system of KH transmitters and OEM transmitters for
encoded data as well as LC Series or LR Series transmitters for custom data.
When using the KH for custom data transmissions, it is important to realize that
there is no encoding or decoding done internally. It is up to the designer to
implement a noise tolerant protocol to ensure the integrity of the data. The
section titled Protocol Guidelines in this manual will give some suggestions as
well as application note #AN00160.
The KH Receiver uses the LC Series receiver, which has a CMOS compatible
output capable of directly driving a microprocessor, RS232 level converter, or a
Linx QS Series USB module. The LC Series receiver manual can be consulted
for more details on the operation of the receiver itself.
214 Clocks
Yes
Data to Output &
Activate VT
No
Address or
Data Error?
The oscillator is disabled in the standby state
Yes
and activated as long as a logic “high” signal
is applied to the DATA line so the DATA line
Figure 9: Decoder Flowchart
should be kept “low” if there is no signal input.
Encoder
Transmit
Enable
Encoder
Data Out
3 Words
2 Words
Check
Check
< 1 Word
Transmitted Continuously
214 Clocks
3 Words
POWER SUPPLY REQUIREMENTS
The module does not have an internal voltage
Vcc TO
regulator; therefore it requires a clean, well-regulated
MODULE
power source. While it is preferable to power the unit
10Ω
from a battery, the unit can also be operated from a
Vcc IN
power supply as long as noise and ‘hash’ are less than
10µF
20mV. Power supply noise will manifest itself as noise
and can significantly affect the receiver sensitivity,
therefore, providing a clean power supply for the
module should be a high design priority.
Figure 11: Supply Filter
A 10Ω resistor in series with the supply followed by a 10µF tantalum capacitor
from Vcc to ground will help in cases where the quality of supply power is poor.
Note that operation from 4.3 to 5.2 volts requires the use of an external 330Ω
resistor placed in-line with the supply to prevent Vcc from exceeding 3.6 volts,
so the dropping resistor can take the place of the 10Ω resistor in the supply filter.
These values may need to be adjusted depending on the noise present on the
supply line.
+
Decoder VT
Decoder
Data Out
1/2 Clock Time
1/2 Clock Time
Figure 10: Encoder/Decoder Timing Diagram
SETTING THE RECEIVER ADDRESS
The module provides ten tri-state address lines. This allows for the formation of
up to 3
10
or 59,049 unique receiver-transmitter relationships. Tri-state means
that the address lines have three distinct states: high, low, and floating. These
lines 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
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.
Naturally 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 #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
The figure below shows an example of a basic remote control receiver utilizing
the KH Series receiver. When a key is pressed on the transmitter, a
corresponding line on the receiver goes high. A schematic for the transmitter /
encoder circuit may be found in the KH Series transmitter data guide. These
circuits are implemented in the KH Series Basic Evaluation kit. These circuits
can be easily modified for a custom application and clearly demonstrate the ease
of using the Linx KH Series modules for remote control applications.
VCC
BZ1
BUZZER
VCC
S4
Q1
2N2222
R2
2.2K
RXD-***-KH
1
2
R4
10K
GND
LED1
RED LED
VCC
VCC
GND
3
4
5
6
R6
220 OHM
Q2
2N2222
7
8
R3
2.2K
9
10
11
12
R5
10K
GND
13
14
NC
D0
D1
GND
VCC
PDN
D2
D3
D4
DATA
VT
D5
D6
D7
ANT
GND
NC
NC
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
28
BNC
27
GND
26
25
24
23
22
21
20
19
SW-DIP-10
18
17
16
15
GND
GND
S1
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
ANT1
B1
CR2032 3V LITHIUM
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 designer’s first
responsibility is to eliminate interference from sources under their control. 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 products sharing the same frequency in
proximity 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 always
important to remember that only one transmitter at a time can occupy a
frequency regardless of the coding of the transmitted signal. In most instances,
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
Figure 12: Basic Remote Control Receiver
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 line outputs can only source about 1mA of current so transistor buffers
are used to drive the buzzer and LED. 1mA is sufficient to activate most
microcontrollers, but the manufacturer’s data guides should be consulted to
make sure.
The KH Series receiver / decoder module is also suitable for use with the Linx
OEM handheld transmitters. These transmitters are FCC certified making
product introduction extremely quick. Information on these transmitters can be
found on the Linx website at www.linxtechnologies.com.
Figure 13: Linx OEM Transmitters
Figure 14: Linx OEM Keyfobs
Page 9
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