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1、AppNote 404 Copyright 2002, EM Microelectronic-Marin SA Application Note 404 Title: EM4095 Application Note Product Family: RFID Part Number:EM4095 Keywords:RFID Transceiver, Reader Chip, EM4095 Date:25 September 2002 TABLE OF CONTENT 1Introduction.2 2Operational Description.3 2.1Resonant circuit pa
2、rameters.3 2.2EM4095 architecture .4 2.3System performance evaluations .4 3Design tips.5 3.1Board design .5 3.2Power supply stability.5 3.3Analog ground pin AGND.5 3.4Design of DEMOD_IN capacitive divider.5 3.5Maximum current on ANT driver outputs.5 3.6Signal MOD.5 3.7Band pass filter tuning.5 4Calc
3、ulating an example .7 4.1Reader antenna properties.7 4.1.1Reader antenna inductivity.7 4.1.2Reader antenna resistance .7 4.1.3Resonant capacitor .7 4.1.4Reader antenna current and voltage.7 4.1.5Reader antenna quality factor .7 4.2Capacitor divider.8 4.3Real Resonant frequency:.8 4.4Sensitivity to r
4、eader antenna signal.8 4.5Power dissipation .8 4.6Temperature.9 4.7Signal damping.9 4.8Band-pass filter tuning.9 5Interfacing a read-only transponder: e.g. EM4100.10 5.1Microcontroller interface .10 5.1.1Sleep mode (SHD) .10 5.1.2Modulation (MOD).10 5.1.3Ready and clock signal (RDY/CLK).10 5.2Comman
5、d transmission (uplink).10 5.3Signal reception on DEMOD_IN.10 6Interfacing a read/write transponder: e.g. EM4069.11 6.1Microcontroller interface .11 6.1.1Sleep mode (SHD) .11 6.1.2Modulation (MOD).11 6.1.3Ready and clock signal (RDY/CLK).11 6.2Command transmission (uplink).11 6.3Signal reception on
6、DEMOD_IN.12 7Interfacing a read/write transponder: e.g. EM4150.13 7.1Microcontroller interfache .13 7.1.1Sleep mode (SHD) .13 7.1.2Modulation (MOD).13 7.1.3Ready and clock signal (RDY/CLK).13 7.2Command transmission (uplink).13 8Schematic and PCB.14 8.1Schematic of the EM4095 demo board .14 8.2Print
7、ed Circuit Board (PCB) of the EM4095 demo board .14 EM MICROELECTRONIC - MARIN SA AppNote 404 Copyright 2002, EM Microelectronic-Marin SA 1 Introduction This application note introduces the CMOS integrated transceiver circuit EM4095 for RFID applications working with transponders at a frequency of t
8、ypically 125 kHz. The paper describes the interoperability with a read-only and a read/write transponder in specific examples. The application note offers helpful design guidelines. Firstly, an technical overview on the EM4095 is given. Secondly, the designer obtains practical design tips. Designing
9、 a typical reader circuit setup is shown by an example in the 4th chapter. The following chapters explain the interoperability of the EM4095 with read-only and read/write transponders. Finally, EM Microelectronic-Marin SA offers a plug-and- play schematic for a typical reader setup using the EM4095.
10、 The corresponding PCB source files will be directly available from the homepage . EM4095 Advantages low cost of external components ensured operation in resonance bigger area of reliable AM modulation easier analyze and system design due to only two system variables precise sampling positioning sim
11、ple to use low power consumption Figure 1: Pin Assignement EM4095 features Integrated PLL system to achieve self adaptive carrier frequency to antenna resonant frequency No external quartz required 100 kHz to 150 kHz carrier frequency range Direct antenna driving using bridge drivers Data transmissi
12、on by OOK (100% Amplitude Modulation) using bridge driver Data transmission by Amplitude Modulation with externally adjustable modulation index using single ended driver Multiple transponder protocol compatibility (e.g. EM400X, EM4050, EM4150, EM4070, EM4170, EM4069) Sleep mode 1A USB compatible pow
13、er supply range -40C to +85C temperature range Small outline plastic package SO16 or PSOP2 16 P +5V LA CDV1 CDV2 CRES EM4095 2 3 4 5 6 7 8 1 15 14 13 12 11 10 9 16 +5V RDY/CLK C DEC C AGND MOD DEMOD_OUT SHD C DC2 C FCAP Figure 2: Typical operating configuration for read only mode SO16 VSS RDY/CLK AN
14、T1 DVDD DVSS ANT2 DC2 FCAP SHD DEMOD_OUT MOD AGND VDD CDEC_IN DEMOD_IN CDEC_OUT AppNote 404 Copyright 2002, EM Microelectronic-Marin SA 2 Operational Description Technical background on how the EM4095 transceiver is operating is given in this chapter. 2.1 Resonant circuit parameters In RFID system w
15、here RF frequency is defined by resonator there are three variables (resonant frequency of antenna, resonant frequency of transponder and RF driving frequency). In system using PLL there are only two variables, since the resonant frequency of the antenna and the RF driving frequency are the same. Th
16、e analysis shows that for a system having defined tolerances on antenna and transponder side the range where one demodulation chain (AM) with fixed sampling point can be used is much larger for PLL system. In fact taking in account technically achievable tolerances the resonator system using one sam
17、pling point is not feasible, two channels with 90 shifted sampling points are needed (AM/FM). This leads to more expensive system which is also more complex to operate. A PLL system with one sampling point has also limitations for tolerance range of transponder and antenna. As a general rule can be
18、notified; the higher the quality factors of the two resonant circuits are, the lower tolerances are acceptable (this is also true for a resonator system). An RFID system with air transponder coils is normally not problematic. For transponders with a Q lower than 15, a tolerance of 5 kHz on the anten
19、na and transponder side is acceptable. Transponders with ferrite core coils have usually higher quality factors (up to 40) and are therefore much more sensitive to tolerances. Figure 3: EM4095 Block Diagram VDD SHD AGND VSS to all blocks LOOP FILTER VCO in this case the connection to the printed coi
20、l should be disabled. When using an external coil the resonance capacitors should be changed, so that the circuit is tuned to resonance. Details are described in the EM4095 application note. So, if you want to connect your own antenna to the Development Kit EM4095, you will have to: Disconnect the i
21、ntegrated coil by cutting the two nets, which are connected, to LB1 however, our design, which also has an air coil, the Q factor is calculated at 34.9. Is this ok, given that EMs recommendation is to take Q value as high as possible? Answer: A quality factor of 35 should give you improved detection
22、 distance, while affecting the data transfer rate. The recovery time to switch from one state to another is higher due to the increased time to dampen the oscillation. EM MICROELECTRONIC - MARIN SA AppNote 403 Copyright 2001, EM Microelectronic-Marin SA Question: Im using the EM4095 demoboard. How d
23、o I have to initialise the system in Write mode? (Bitmuster, Timing). With which data rate can EM4150 Transponders be programmed? Answer: The data rate of the EM4150 RFID transponder depends on the chip version that you have selected. Please refer to the last page of the corresponding data sheet. Co
24、ncerning your write mode problems, it could be due to one of the following causes: The transponders main supply. In effect, notice in EM4150 datasheet (Page 3), that the supply current/write is 15 times bigger than the supply current/read. It means that the reading distance is always bigger than the
25、 write distance. One solution will be to reduce the distance between transponder and transceiver. A chip write protection. If you lock a part or the complete EEPROM area, your chip will protect all its data. For more information you could refer to the EM4150 datasheet, fig.6 To write on a chips memo
26、ry, youve to wait for a LIW (Listen Window). At this moment your transceiver must send the RM pattern and the write command. If you send your command without waiting for a LIW, the transponder wont understand the command. In write mode, you dont need to initialize anything. The chip initialization i
27、s made just after the chips Power On Reset. Question: Our customer is using the EM4095 reader demoboard and needs the specification of the serial protocol (Start/stop bit etc.) to interface a microcontroller. Is an encrypted protocol version of the EM4095 in the roadmap? Our customer would like to copy the EM4095 reader demoboard layout for its application. Which program was used (eg. Orcad. Eagle) to create the layout file? Answer: Concerning your first question, the serial protocol sent by the microcon