TXM-418-LC

LC Series Transmitter Module Data Guide ! Warning: Some customers may want Linx radio frequency (“RF”) products to control machinery or devices remotely, including machinery or devices that can cause death, bodily injuries, and/or property damage if improperly or inadvertently triggered, particularly in industrial settings or other applications implicating life-safety concerns (“Life and Property Safety Situations”). Table of Contents 1^ 1^ 1^ NO OEM LINX REMOTE CONTROL OR FUNCTION MODULE SHOULD EVER BE USED IN LIFE AND PROPERTY SAFETY SITUATIONS. No OEM Linx Remote Control or Function Module should be modified for Life and Property Safety Situations. Such modification cannot provide sufficient safety and will void the product’s regulatory certification and warranty. 2^ Customers may use our (non-Function) Modules, Antenna and Connectors as part of other systems in Life Safety Situations, but only with necessary and industry appropriate redundancies and in compliance with applicable safety standards, including without limitation, ANSI and NFPA standards. It is solely the responsibility of any Linx customer who uses one or more of these products to incorporate appropriate redundancies and safety standards for the Life and Property Safety Situation application. 7^ Do not use this or any Linx product to trigger an action directly from the data line or RSSI lines without a protocol or encoder/ decoder to validate the data. Without validation, any signal from another unrelated transmitter in the environment received by the module could inadvertently trigger the action. All RF products are susceptible to RF interference that can prevent communication. RF products without frequency agility or hopping implemented are more subject to interference. This module does have a frequency hopping protocol built in, but the developer should still be aware of the risk of interference. Do not use any Linx product over the limits in this data guide. Excessive voltage or extended operation at the maximum voltage could cause product failure. Exceeding the reflow temperature profile could cause product failure which is not immediately evident. Do not make any physical or electrical modifications to any Linx product. This will void the warranty and regulatory and UL certifications and may cause product failure which is not immediately evident. 2^ 3^ 4^ 7^ 8^ 9^ 9^ 10^ 11^ 12^ 12^ 13^ 14^ 15^ 15^ 16^ 17^ 17^ 19^ 20^ 20^ 20^ 22^ 24^ Description Features Applications Ordering Information Absolute Maximum Ratings Electrical Specifications Typical Performance Graphs Pin Assignments Pin Descriptions Module Description Theory of Operation The Data Input Adjusting the Output Power Transferring Data Power Supply Requirements Typical Applications ESD Concerns Antenna Considerations Helpful Application Notes from Linx Protocol Guidelines Interference Considerations Pad Layout Board Layout Guidelines Microstrip Details Production Guidelines Hand Assembly Automated Assembly General Antenna Rules Common Antenna Styles  26^ Regulatory Considerations LC Series Transmitter Module Data Guide Description 0.360 in The LC Series is ideally suited for volume use in (9.14 mm) TXM-315-LC OEM applications such as remote control, security, LOT CTxxxx identification and periodic data transfer. Housed 0.500 in in a compact surface-mount package, the LC (12.7 mm) Series transmitter utilizes a highly-optimized SAW 0.150 in Max. (3.81 mm) architecture to achieve an unmatched blend of performance, size, efficiency and cost. When Figure 1: Package Dimensions paired with a matching LR Series receiver, a highly reliable wireless link is formed, capable of transferring serial data at distances of up to 3,000 feet. No external RF components are required (except an antenna), making design and integration straightforward, even for engineers without previous RF experience. Features • Low cost • No external RF components required • Ultra-low power consumption • Compact surface-mount package • Stable SAW-based architecture • Supports data ranges to 5,000bps • Wide supply range (2.7 to 5.2VDC) • Direct serial interface • Low harmonics • No production tuning Applications • • • • • • Remote control Keyless entry Garage/gate openers Lighting control Medical monitoring/call systems Remote industrial monitoring • • • • • • – 1– Periodic data transfer Home/industrial automation Fire/security alarms Remote status/position sensing Long-range RFID Wire elimination Revised 3/18/14 Ordering Information Electrical Specifications Ordering Information LC Series Transmitter Specifications Part Number Description TXM-315-LC 315MHz Transmitter TXM-418-LC 418MHz Transmitter TXM-433-LC 433MHz Transmitter EVAL-***-LC LC Series Basic Evaluation Kit Parameter Symbol Min. Operating Voltage VCC 2.7 Supply Current lCC Power Down Current lPDN Typ. Max. Units Notes 5.2 VDC 6.0 mA 1,4 1.5 µA 2 Power Supply *** = 315, 418 (Standard), 433MHz Transmitters are supplied in tubes of 50 pcs. 3.0 Transmitter Section Transmit Frequency Figure 2: Ordering Information Absolute Maximum Ratings FC TXM-315-LC 315 MHz TXM-418-LC 418 MHz TXM-433-LC 433.92 MHz Center Frequency Accuracy Absolute Maximum Ratings –75 Supply Voltage Vcc −0.3 to +6.0 VDC Output Power PO Any Input or Output Pin −0.3 to VCC VDC Harmonic Emissions PH Operating Temperature −30 to +70 ºC Data Rate Storage Temperature −45 to +85 ºC Data Input Soldering Temperature +260ºC for 10 seconds 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. –4 0 +75 kHz +4 dBm 3 –36 dBc 3 100 5,000 bps Logic Low VIL 0.0 0.4 VDC Logic High VIH 2.5 VCC VDC Antenna Port RF Output Impedance ROUT Ω 5 80 µSec 5 100 nSec 5 +70 ºC 5 50 Timing Figure 3: Absolute Maximum Ratings Transmitter Turn-On Time Warning: 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. 30 Transmitter Turn-Off Time Environmental Operating Temperature Range 1. 2. Current draw with DATA pin held continuously high Current draw with DATA pin low –30 3. 4. 5. Figure 4: Electrical Specifications – 2– – 3– RF out connected to a 50Ω load LADJ through a 430Ω resistor Characterized, but not tested Supply Current (mA) Typical Performance Graphs 12 11 10 9 8 7 6 5 4 3 2 1 0 2.5 3.0 3.5 4.0 4.5 Supply Voltage (V) 5.0 With LADJ tied to ground With 430Ω resistor on LADJ Figure 7: Typical Oscillator Turn-On Time Output Power (dBm) Figure 5: Current vs. Supply Voltage +8 +7 +6 +5 +4 +3 +2 +1 0 -1 -2 -3 -4 -5 2.5 3.0 3.5 4.0 4.5 Supply Voltage (V) 5.0 With LADJ tied to ground With 430Ω resistor on LADJ Figure 6: Output Power vs. Supply Voltage – 4– Figure 8: Oscillator Turn-Off Time – 5– Output Power (dBm) +8 +7 +6 +5 +4 +3 +2 +1 0 -1 -2 -3 -4 Pin Assignments 1 2 3 4 5V 3V 51 100 150 200 240 300 360 430 510 560 620 680 750 820 910 1.1K LADJ Resistor Value (Ω) Figure 9: Output Power vs. LADJ Resistor GND GND DATA VCC GND GND LADJ/GND ANT 8 7 6 5 Figure 10: LC Series Transmitter Pinout (Top View) Pin Descriptions Pin Descriptions Pin Number Name I/O Description 1 GND — Analog Ground 2 DATA I 3 GND — Digital Data Input Analog Ground Level Adjust. This line is used to adjust the output power level of the transmitter. Connecting to ground gives the highest output, while pacing a resistor to ground lowers the output level (see Figure 9 on page 6) 4 LADJ/GND I 5 ANT — 50-ohm RF Output 6 GND — Analog Ground 7 VCC — Supply Voltage 8 GND — Analog Ground Figure 11: Pin Descriptions – 6– – 7– Module Description Theory of Operation The LC Series transmitter is a low-cost, high-performance Surface Acoustic Wave (SAW) based Carrier-Present Carrier-Absent (CPCA) transmitter capable of sending serial data at up to 5,000bps. The LC’s compact surface-mount package integrates easily into existing designs and is equally friendly to prototype and volume production. Its ultra-low power consumption makes it ideally suited for battery-powered products. The LC Series transmitter transmits data using Carrier-Present CarrierAbsent (CPCA) modulation. This type of AM modulation is often referred to by other designations, including Continuous Wave (CW) and On-Off Key (OOK). This type of modulation represents a logic low ‘0’ by Data the absence of a carrier and a logic high ‘1’ Carrier by the presence of a carrier. This method affords numerous benefits. Three of the most Figure 13: CPCA (AM) Modulation important are: The transmitter’s output power varies with supply voltage, but it is capable of outputting +10dBm into a 50-ohm load. When combined with an LR Series receiver, a reliable serial link is formed capable of transferring data over line-of-site distances of up to 1.5 miles (2,500m) when used with good antennas. Legal regulations in the various countries will require the transmitter output power to be reduced which will reduce range. Following the legal output limit for transmitters in the United States, systems based on the LC Series transmitter and LR Series receiver can achieve ranges of up to 3,000 feet (1,000m). SAW Oscillator 50Ω RF OUT (ANT) Data In 300-5,000bps Keyed Output Output Isolation & Filter Vcc RF Amplifier Figure 12: LC Series Transmitter Block Diagram 1) Cost-effectiveness due to design simplicity. 2) No minimum data rate or mark / space ratio requirement. 3) Higher output power and thus greater range in countries (such as the U.S.) where output power measurements are averaged over time. (Please refer to Linx Application Note AN-00130). The LC Series transmitter is based on a simple but highly optimized architecture that achieves a high fundamental output power with low harmonic content. This ensures that approval requirements can be met without external filter components. The LC Series transmitter is exceptionally stable over time, temperature, and physical shock as a result of the precision Surface Acoustic Wave (SAW) frequency reference. Due to the accuracy of the SAW device, most of the output power is concentrated in a narrow bandwidth. This allows the receiver’s bandwidth to be quite narrow, thus increasing sensitivity and reducing susceptibility to near-band interference. The quality of components and overall architecture utilized in the module is extraordinary in a low-cost RF device and is one reason why the LC Series transmitter is able to outperform more expensive products. The Data Input A CMOS / TTL level data input is provided on Pin 2. This line is normally supplied with a serial bit stream input directly from a microprocessor, encoder or UART. During standby, or the input of a logic low, the carrier is fully suppressed and the transmitter consumes less than 2μA of current. During a logic high, the transmitter generates a carrier to indicate to the receiver the presence of a logic ‘1’. The applied data should not exceed a rate of 5,000bps. The data input line should always be driven with a voltage common to the supply voltage present on Pin 7 (VCC) and should never be allowed to exceed the supply voltage. – 8– – 9– Adjusting the Output Power Transferring Data Depending on the type of antenna being used and the duty cycle of the data, the output power of the LC Series transmitter module may be higher than FCC regulations allow. The output power of the module is intentionally set high to compensate for losses resulting from inefficient antennas that may be used to realize cost or space savings. Since attenuation is often required, it is generally wise to provide for its implementation and allow the FCC test lab to easily attenuate the transmitter to the maximum legal limit for your product. Once a reliable RF link has been established, the challenge becomes how to effectively transfer data across it. While a properly designed RF link provides reliable data transfer under most conditions, there are still distinct differences from a wired link that must be addressed. The LC Series is intended to be as transparent as possible and does not incorporate internal encoding or decoding, so a user has tremendous flexibility in how data is handled. Two methods of attenuation are available using the LC Series transmitter module. First, a resistor may be placed between Pin 4 (LADJ) and ground to achieve up to a 7dB reduction in output power. The resistor value is easily determined from Figure 9 on page 6. Do not exceed the resistance values shown as transmitter instability may result. This method can also be used to reduce the transmission range and power consumption. Another method commonly used to achieve attenuation, particularly at higher levels, is the use of a T-pad attenuator. A T-pad is a network of three resistors that allows for variable attenuation while maintaining the correct match to the antenna. It is usually prudent to allow space for the addition of a T-pad. An example of a T-pad attenuator layout is shown in Figure 14. For further details on T-pad attenuators, please refer to Application Note AN-00150. TYPICAL LAYOUT CIRCUIT WITH PROVISION FOR ATTENUATION ANT PADS FOR SMD RESISTORS R1 R1 ANT R2 GROUND PLANE ON LOWER LAYER GROUND GND ANT OUT TXM-xxx-LC LOT CTxxxx If the product transfers simple control or status signals such as button presses or switch closures and it does not have a microprocessor on board (or it is desired to avoid protocol development), consider using a remote control encoder and decoder or a transcoder IC. These chips are available from a wide range of manufacturers including Linx. They take care of all encoding and decoding functions, and generally provide a number of data pins to which switches can be directly connected. In addition, address bits are usually provided for security and to allow the addressing of multiple units independently. These ICs are an excellent way to bring basic remote control / status products to market quickly and inexpensively. Additionally, it is a simple task to interface with inexpensive microprocessors, IR, remote control or modem ICs. It is always important to separate the types of transmissions that are technically possible from those that are legally allowable in the country of intended operation. Linx Application Notes AN-00125, AN-00128 and AN-00140 should be reviewed, along with Part 15, Section 231 of the Code of Federal Regulations for further details regarding acceptable transmission content in the US All of these documents can be downloaded from the Linx website at www.linxtechnologies.com. Another area of consideration is that the data structure can affect the output power level. The FCC allows output power in the 260 to 470MHz band to be averaged over a 100ms time frame. Because OOK modulation activates the carrier for a ‘1’ and deactivates the carrier for a ‘0’, a data stream that sends more ‘0’s has a lower average output power over 100ms. This allows the instantaneous output power to be increased, thus extending range. Figure 14: A T-Pad Attenuator Layout Example – 10 – – 11 – Power Supply Requirements The module does not have an internal Vcc TO MODULE voltage regulator; therefore it requires a clean, well-regulated power source. While 10Ω it is preferable to power the unit from a Vcc IN battery, the unit can also be operated from 10µF a power supply as long as noise is less than 20mV. Power supply noise can significantly affect the transmitter modulation; therefore, providing a clean power supply for the Figure 15: Supply Filter module should be a high design priority. + A 10-ohm 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. These values may need to be adjusted depending on the noise present on the supply line. Typical Applications The LC Series transmitter is ideal for the transmission of remote control / command data. One of the easiest way to transmit on / off data or switch closures is to use an encoder and decoder. These ICs provide a number of data lines that can be connected to switches or buttons or even a microcontroller. When a line is taken high on the encoder, a corresponding line goes high on the decoder as long as the address matches. Figure 16 shows an example using the Linx MS Series encoder. 750 1 GND GND 2 DATA VCC 3 GND GND 4 LADJ/GND ANT 8 7 6 5 TXM-xxx-LC 100k 100k 220 1 2 3 4 5 6 7 8 9 10 0 The MS Series Encoder Data Guide explains this circuit and the many features of the encoder in detail, so please refer to that document for more information. A 750-ohm resistor is used on the LADJ line of the transmitter to reduce the output power of the transmitter. This is appropriate for some antennas, but may need to be adjusted depending on the design. Typically, a resistor pad is placed on the board and a potentiometer is used by the FCC test lab to adjust the output power to the maximum legal limit. The potentiometer value is measured and the closest standard value resistor is placed for final testing. If the level adjust resistor does not provide enough attenuation, a T-pad attenuator can be placed between the transmitter and antenna. This is a network of three resistors that provides a set amount of attenuation while maintaining a 50-ohm match between the antenna and the transmitter. Application Note AN-00150 gives the formulas for calculating the resistor values. If not needed, the series resistors can be zero ohms or shorted and the parallel one not placed. ESD Concerns 0 OPEN D6 D5 D7 D4 SEL_BAUD0 D3 SEL_BAUD1 D2 GND VCC GND VCC GND D1 TX_CNTL D0 DATA_OUT SEND MODE_IND CREATE_ADDR This circuit uses the LC Series transmitter and the MS Series encoder to transmit button presses. The MS Series has eight data lines, which are connected to buttons that pull the line high when pressed. When not used, the lines are pulled low by 100k-ohm resistors. The encoder begins a transmission when the SEND line is taken high. Diodes are used to pull this line high when any data line is pulled high while isolating the data lines from each other. 20 19 18 17 16 15 14 13 12 11 100k 100k 100k 100k The module has basic ESD protection built in, but in cases where the antenna connection is exposed to the user it is a good idea to add additional protection. A Transient Voltage Suppressor (TVS) diode, varistor or similar component can be added to the antenna line. These should have low capacitance and be designed for use on antennas. Protection on the supply line is a good idea in designs that have a user-accessible power port. 100k 100k 220 100k LICAL-ENC-MS001 Figure 16: LC Series Transmitter and MS Series Encoder – 12 – – 13 – Antenna Considerations Helpful Application Notes from Linx The choice of antennas is a critical and often overlooked design consideration. The range, performance and legality of an RF link are critically dependent upon the antenna. While adequate antenna performance can often be obtained by trial and error methods, antenna Figure 17: Linx Antennas design and matching is a complex task. Professionally designed antennas such as those from Linx (Figure 17) help ensure maximum performance and FCC and other regulatory compliance. It is not the intention of this manual to address in depth many of the issues that should be considered to ensure that the modules function correctly and deliver the maximum possible performance. We recommend reading the application notes listed in Figure 18 which address in depth key areas of RF design and application of Linx products. These applications notes are available online at www.linxtechnologies.com or by contacting Linx. Linx transmitter modules typically have an output power that is higher than the legal limits. This allows the designer to use an inefficient antenna such as a loop trace or helical to meet size, cost or cosmetic requirements and still achieve full legal output power for maximum range. If an efficient antenna is used, then some attenuation of the output power will likely be needed. This can easily be accomplished by using the LADJ line. A receiver antenna should be optimized for the frequency or band in which the receiver operates and to minimize the reception of off-frequency signals. The efficiency of the receiver’s antenna is critical to maximizing range performance. Unlike the transmitter antenna, where legal operation may mandate attenuation or a reduction in antenna efficiency, the receiver’s antenna should be optimized as much as is practical. It is usually best to utilize a basic quarter-wave whip until your prototype product is operating satisfactorily. Other antennas can then be evaluated based on the cost, size and cosmetic requirements of the product. Additional details are in Application Note AN-00500. Helpful Application Note Titles Note Number Note Title AN-00100 RF 101: Information for the RF Challenged AN-00125 Considerations for Operation Within the 260–470MHz Band AN-00130 Modulation Techniques for Low-Cost RF Data Links AN-00140 The FCC Road: Part 15 from Concept to Approval AN-00150 Use and Design of T-Attenuation Pads AN-00160 Considerations for Sending Data over a Wireless Link AN-00232 General Considerations for Sending Data with the LC Series AN-00500 Antennas: Design, Application, Performance AN-00501 Understanding Antenna Specifications and Operation Figure 18: Helpful Application Note Titles 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, read Linx Application Note AN-00160. Interference or changing signal conditions can corrupt 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. – 14 – – 15 – Interference Considerations Pad Layout The RF spectrum is crowded and the potential for conflict with 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. The pad layout diagram in Figure 19 is designed to facilitate both hand and automated assembly. 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 produces noise and hashing on the output and reduces 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 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 shorter useful distances for the link. 0.065" 0.340" 0.070" 0.100" Figure 19: Recommended PCB Layout Board Layout Guidelines The module’s design makes integration straightforward; however, it is still critical to exercise care in PCB layout. Failure to observe good layout techniques can result in a significant degradation of the module’s performance. A primary layout goal is to maintain a characteristic 50-ohm impedance throughout the path from the antenna to the module. Grounding, filtering, decoupling, routing and PCB stack-up are also important considerations for any RF design. The following section provides some basic design guidelines. During prototyping, the module should be soldered to a properly laid-out circuit board. The use of prototyping or “perf” boards results in poor performance and is strongly discouraged. Likewise, the use of sockets can have a negative impact on the performance of the module and is discouraged. The module should, as much as reasonably possible, be isolated from other components on your PCB, especially high-frequency circuitry such as crystal oscillators, switching power supplies, and high-speed bus lines. When possible, separate RF and digital circuits into different PCB regions. – 16 – – 17 – Make sure internal wiring is routed away from the module and antenna and is secured to prevent displacement. Do not route PCB traces directly under the module. There should not be any copper or traces under the module on the same layer as the module, just bare PCB. The underside of the module has traces and vias that could short or couple to traces on the product’s circuit board. The Pad Layout section shows a typical PCB footprint for the module. A ground plane (as large and uninterrupted as possible) should be placed on a lower layer of your PC board opposite the module. This plane is essential for creating a low impedance return for ground and consistent stripline performance. Use care in routing the RF trace between the module and the antenna or connector. Keep the trace as short as possible. Do not pass it under the module or any other component. Do not route the antenna trace on multiple PCB layers as vias add inductance. Vias are acceptable for tying together ground layers and component grounds and should be used in multiples. Microstrip Details A transmission line is a medium whereby RF energy is transferred from one place to another with minimal loss. This is a critical factor, especially in high-frequency products like Linx RF modules, because the trace leading to the module’s antenna can effectively contribute to the length of the antenna, changing its resonant bandwidth. In order to minimize loss and detuning, some form of transmission line between the antenna and the module should be used unless the antenna can be placed very close (