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 over distances in excess of 300
feet. Ten tri-state address lines provide 59,049
(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, are required (except an antenna),
making design integration straightforward.
1.430"
0.630"
LOT 1000
RF RECEIVER/DECODER
RXD-418-KH
0.180"
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
TXE-315-KH
Transmitter / Encoder 315MHz
TXE-418-KH
Transmitter / Encoder 418MHz
TXE-433-KH
Transmitter / Encoder 433MHz
RXD-315-KH
Receiver / Decoder 315MHz
RXD-418-KH
Receiver / Decoder 418MHz
RXD-433-KH
Receiver / Decoder 433MHz
EVAL-***-KH
Basic Evaluation Kit
*** = Frequency
Receivers are supplied in tubes of 20 pcs.
Revised 10/12/06
ELECTRICAL SPECIFICATIONS
Parameter
POWER SUPPLY
Operating Voltage:
With Dropping Resistor
Supply Current
Power-Down Current
V
CC
I
CC
I
PDN
F
C
–
–
–
-75
–
–
100
0.0
V
CC
- 0.3
-92
–
50
–
Ω
–
–
–
-102
0.3
V
CC
-106
VDC
VDC
dBm
3
3,4
5
315
418
433.92
–
10.7
280
–
–
–
–
+75
–
–
5,000
MHz
MHz
MHz
kHz
MHz
kHz
bps
–
–
–
–
–
2
–
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
–
–
RECEIVER SECTION
Receive Frequency:
RXD-315-KH
RXD-418-KH
RXD-433-KH
Center Frequency Accuracy
IF Frequency
Noise Bandwidth
Data Rate
Data Output:
Logic Low
Logic High
Receiver Sensitivity
–
F
IF
N
3DB
–
V
OL
V
OH
–
R
IN
ANTENNA PORT
RF Input Impedance
TIMING
Receiver Turn-On Time:
Via V
CC
–
–
–
F
ENC
–
–
-30
0.6
1.0
–
–
–
–
26 bits 3x
50%
70
–
–
–
1.2
+70
5.0
7.0
10.5
DECODER SECTION
TX Data Length
Average Data Duty Cycle
Decoder Oscillator
Output Drive Current
ENVIRONMENTAL
Operating Temperature Range
–
–
kHz
mA
–
–
–
7
mSec
6
Designation
Min.
Typical
Max.
Units
Notes
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
CC
Supply Voltage V
CC
, Using Resistor
Any Input or Output Pin
RF Input
Operating Temperature
Storage Temperature
Soldering Temperature
-0.3
to
+4.2
-0.3
to
+5.2
-0.3
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.
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. The pins marked NC
have no electrical connection and
are designed only to add physical
support.
5VDC
200Ω
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
Figure 2: Test / Basic Application Circuit
TYPICAL PERFORMANCE GRAPHS
°
C
–
10.0
10.0
6.0
5.0
4.0
3.0
3.0
2.5
2.0
2.0
1.5
1.0
1.0
Supply Current (mA)
Table 1: KH Series Receiver Electrical Specifications
16
16
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 V
CC
.
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.
V
CC
referenced to voltage on the V
CC
pin after dropping resistor.
For a BER of 10-5 at 4,800 baud. Sensitivity is affected by the antenna’s SWR.
Time to valid data output.
Maximum drive capability of data outputs.
4.
5.
6.
7.
VSWR
12
12
8
4
0 0.18 0.5 0.9 1.25 1.94 2.53 3.10 4.80
0.18 0.5 0.9 1.25 1.94 2.53 3.10 4.80
0
Sensitivity Decrease (dB)
Sensitivity Decrease (dB)
Figure 3: Sensitivity vs. VSWR
2.7
3
3.5
4
Supply Voltage (V)
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 5: RF In vs. Receiver Response Time
Figure 6: Receiver Turn-Off Time
Page 3
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
50Ω RF IN
(Ant.)
Band Select
Filter
pre-
amplifier
MODULE DESCRIPTION
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
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 is formed,
capable of transferring control and command data over line-of-sight distances in
excess of 300 feet. 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 (3
10
) unique identification codes.
Gilbert Cell
Mixer/Amp
RF Stage
10.7MHz
Bandpass Filter
DATA
Figure 7: KH Series Receiver Pinout (Top View)
10.7MHz
AM Detector
Limiting Amp Ceramic Filter
Data Slicer
PIN DESCRIPTIONS
Pin #
1
2, 3, 7, 8,
9, 12, 13,
14
D0-D7
4
5
V
CC
GND
Analog Ground
Supply Voltage
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.
A0-A9
NC
26
27
28
Page 4
Name
NC
No Connection. For physical support only.
Description
SAW Local Oscillator
Decoder Stage
Oscillator
Divider
Data Output Lines. Upon a valid transmission, these lines
will be set to replicate the state of the transmitter’s address
lines.
8-bit
Shift
Register
Buffer
Latch
Circuit
AND
Circuit
Data
Collector
D0
D1
D2
D3
D4
D5
D6
D7
Buffer
Sync.
Detector
Comparator
Comparator
Control
Logic
Transmission Gate Circuit
A0 A1 A2 A3 A4 A5 A6 A7 A8 A9
6
PDN
Figure 8: KH Series Receiver Block Diagram
THEORY OF OPERATION
10
11
VT
DATA
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.
15-24
25
No Connection. For physical support only.
NC
GND
RF IN
No Connection. For physical support only.
Analog Ground
50-ohm RF Input
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 band to be quite
narrow, thus increasing sensitivity and reducing susceptibility to near-band
interference.
Page 5
DECODER OPERATION
The KH Series receiver utilizes the HT658
decoder from Holtek. The decoder receives
data transmitted by the encoder and
interprets the first 10 bits of the code period
as address and the last 8 bits as data. A
signal on the DATA line activates the
oscillator, which in turn decodes the
incoming address and data. The decoder
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. The data outputs are
momentary, and follow the encoder during a
valid transmission, then reset.
Power On
Standby Mode
Disable VT &
Ignore the Rest of
This Word
THE DATA OUTPUTS
No
Code In?
Yes
Address Bits
Matched?
Yes
Store Data
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.
No
Match
Previous Stored
Data?
No
Yes
No
2 Times
of Checking
Completed?
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 line 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.
RECEIVING DATA
Yes
Data to Output &
Activate VT
No
Address or
Data Error?
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 Series or OEM transmitters for encoded
data as well as LC or LR Series transmitters for custom data.
The oscillator is disabled in the standby
Yes
state and activated as long as a logic “high”
signal is applied to the DATA line, so the
Figure 9: Decoder Flowchart
DATA line should be kept “low” if there is no signal input.
Encoder
Transmit
Enable
< 1 Word
When using the KH for custom data transmissions, it is up to the designer to
implement a noise-tolerant protocol to ensure the integrity of the data. The
Protocol Guidelines section will provide some suggestions, as well as Application
Note AN-00160.
Encoder
Data Out
3 Words
2 Words
Check
Check
214 Clocks
The KH Series receiver module contains the LC Series receiver, which has a
CMOS-compatible output capable of directly driving a microprocessor, an RS-
232 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.
Transmitted Continuously
3 Words
214 Clocks
POWER SUPPLY REQUIREMENTS
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 59,049 (3
10
) unique receiver-transmitter relationships. Tri-state means that
the address lines can be set to one of three distinct states: high, low, or 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
A 10Ω resistor in series with the supply followed by a
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. Note that operation from 4.7 to 5.2 volts
requires the use of an external 200Ω resistor placed in-line with the supply to
prevent V
CC
from exceeding 4.2 volts, so the dropping resistor can take the place
of the 10Ω resistor in the supply filter.
Figure 11: Supply Filter
+
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 receiver sensitivity;
therefore, providing a clean power supply for the
module should be a high priority during design.
Vcc TO
MODULE
10Ω
Vcc IN
10μF
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.
VCC
BZ1
BUZZER
TYPICAL APPLICATIONS
The figure below shows an example of a basic remote control receiver utilizing
the KH Series receiver module. 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. They 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
S4
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.
Q1
2N2222
R2
2.2k
ANT1
1
R4
10k
GND
LED1
RED LED
NC
ANT
28
B1
CR2032 3V LITHIUM
2
VCC
VCC
D0
GND
27
GND
3
D1
NC
26
4
GND
NC
25
GND
S1
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
GND
5
VCC
A9
24
6
R6
220 OHM
Q2
2N2222
PDN
A8
23
7
D2
A7
22
8
R3
2.2k
D3
A6
21
9
D4
A5
20
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
10
DATA
A4
19
SW-DIP-10
11
VT
A3
18
12
R5
10k
GND
D5
A2
17
GND
13
D6
A1
16
14
D7
A0
15
RXD-XXX-KH
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 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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