EVB90109 MELEXIS | Alldatasheet
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M LX90109 Evaluation B oard
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M inim um PC B size (30 * 30 m m ) including a M LX90109 transceiver IC and an optim ized antenna Tuned resonance frequency to 125kH z M odulation netw ork on board for a m axim um flexibility Setup for fast O n/O ff keying m odulation m ode D IL-10 footprint for easy m ounting on prototype set up and developm ent kit O rdering Inform ation Part N o. EVB90109 A pplications Exam ples Evaluation B oard C ar Im m obilizers Portable readers Battery pow ered door locks Access control H ouse held appliances G eneral D escription The EVB90109 is an assem bled m odule that allow s evaluating the advantages of the M LX90109 transceiver IC . It w ill facilitate the starts of R FID applications and can be im plem ented in a com pact w ay, w ith m inim um developm ent tim e, and m inim um final system cost. All pins of the M LX90109 reader are available on a D IL socket for easy control w ith an external m icrocontroller. Tw o extra pins have been added for extended control options on the voltage on the M O D U pin. The EVB90109 can be used as a 125 kH z reader, to read out the load m odulation from a transponder. It can also be used to send inform ation to a transponder using O n/O ff keying m odulation. For fast protocol w hich required fast fall tim e on the reader’s antenna, the EVB90109 includes a “Fast decay” circuit com posed of an external transistor and diode in parallel on the antenna. This circuit is accessible through a digital pin on the D IL-10 connector.
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Param eter C ondition Sym bol M in Typ M ax U nits Supply Voltage Vdd 4.5 5 5.5 Volts Resonance frequency Vdd = 5Volts Fres 120 125 130 kHz Table 1: Electrical specifications
2 D escription
2.1 G eneral explanation
The EVB90109 consists of a single chip inductive R FID reader for the 125 kH z frequency range w ith an external inductance (L) and capacitance (C ) connected as a parallel resonant circuit. The antenna voltage am plitude can be set O n/O ff externally w ith the digital line M O D U R 2, w hich controls a resistive and capacitive netw ork called “M odulation netw ork” connected to the M O D U pin of the chip. This allow s m axim um reading distance and reliability, can be used to preserve energy by easily setting the evaluation board in pow er dow n m ode and finally allow s 100% m odulation for reader talk first applications. The EVB90109 also includes a “fast decay” circuit com posed of an external transistor and diode in parallel to the resonant antenna, used to short the antenna for negative sw ings to dissipate the rem aining energy into the transistor and then, to reduce the fall tim e of the antenna. For m ore inform ation, please refer to the application note “100% M odulation (O n/O ff keying)”. An additional footprint of “M odulation netw ork” is available on the board and is accessible through the M O D U R 3 digital connection. All others digital connections as SPEED , M O D E, M O D U , C LO C K and D A TA, are available on the D IL-10 connector. Figure 1: EVB90109 N ote: The EVB90109 does not include any pull-up resistors on the digital connections D ATA and C LO C K. This m ust be done externally, by configuring the IO ports of a m icrocontroller in pull-up m ode, or by adding tw o external resistors connected betw een the digital pins and Vdd. Parallel resonant antenna (L, C4, C5) Fast decay circuit (Q1, MLX90109 Modulation Network (R1, R2) Connector DIL-10
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2.2 Parallel antenna
The parallel antenna of the EVB90109 consists of the inductance (L) based on the M LX90125 reader coil and the tune capacitor (C 4), w hich form a resonant system at 125 kH z w ith a total (inductance and capacitance) antenna im pedance of about 1.3kO hm s. The M LX90109 is specified to drive a m inim al antenna im pedance of 1kO hm , w hich can be theoretically calculated using the follow ing form ula. rresantant LQZ ⋅⋅= ω C are should be taken that the presence of a transponder m ay reduce the theoretical antenna im pedance to be sm aller that the m inim um specified. Therefore it m ay be of interest to take som e extra m argin in the antenna design by taking a slightly higher quality factor to increase the antenna im pedance. A tune capacitance w ith a poor quality factor m ay also reduce the global perform ances of the antenna, as show n in the follow ing form ula. CLant QQQ //= Therefore, the tune capacitance should be taken w ith a high quality factor or low ESR (plastic or m ica) to not reduce the total im pedance of the antenna and m oreover, to not annihilate all the efforts m ade in the design of the antenna to w ork w ith a high quality factor and then to get the m axim um of operating distance.
2.3 M odulation netw ork
The m odulation netw ork is used to set the voltage on the M O D U pin of the M LX90109. As show n in the follow ing form ula, the voltage on the antenna can be adjusted according to this voltage. This features can be used to reduce the pow er consum ption of the chip by setting a low er voltage on the antenna. U nder no circum stances it can be used to m ake proportionnal m odulaiton, due to internal feedback loop w hich doesn’t allow this use. overshootM O D UD Dant VVVV −−= The EVB90109 is provided w ith tw o resistors R 1 and R 2 as the m odulation netw ok controlled through the pin M O D U R 2 to set the voltage on the antenna respectively O n (Vm odu to 0.8 Volts) and O ff (Vm odu to 5 Volts). O thers footprint C 1, C 3 and R 3 and an extra pin M O D U R 3 are available on the board and can be used for specific applications.
2.4 A ntenna voltage in read operation
The resistors R 1 and R 2 set VM O D U to 0.8V (1V for full tem perature range [–40, 85] C ) w hich is the low est possible voltage to guarantee that the antenna driver of the M LX90109 stays out of its linear operating zone. The field is set O n (VM O D U to 0.8V) and O ff (VM O D U to VD D ) w hen applying 0V and VD D on pin M O D U R 2.
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2.5 N oise cancellation in read operation
The resonant antenna is a natural band-pass filter, w hich becom es m ore effective as Q ant increases. The M LX90109 has an internal first order filtering of the envelope that changes according to the setting of the SPEED pin to fit to the biphase and M anchester data spectrum : 2kbaud (speed = 1): 400H z to 3.6kH z 4kbaud (speed = 0): 800H z to 7.2kH z N oise that is injected on M O D U pin or on VD D w ill cause Vant to change, and w ill therefore be considered to be data by the sam pler. This noise can sim ply be cancelled by adding a capacitor C 1 betw een M O D U and VD D . Together w ith the m odulation netw ork R 1 and R 2, its creates a high pass filter w ith cut off frequency at: ( ) 121 //2 CRR ⋅⋅⋅π N ote: D ue to the long tim e constant introduces and the parasitic oscillations that it m ay provoke w ith the transistor Q 1, the capacitor C 1 m ust be rem oved w hen using the EVB90109 in O n/O ff keying m odulation m ode.
2.6 A ntenna voltage in 100% m odulation operation
The m odulation netw ork R 1 and R 2 can be used to set the voltage am plitude on the antenna O n and O ff by applying 0 Volts and Vdd on the pin M O D U R 2. Sw itching O N the m agnetic field depends on the internal driver of M LX90109 and takes less than 5 carrier periods. Sw itching O FF the m agnetic field depend on the quality factor (Q ant) of the parallel antenna connected to the reader (about 24 periods w ith the EVB90109). To reduce this fall tim e, the “fast decay” circuit can be used.
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2.7 Fast decay circuit
Very sm all fall tim e m ay be required in fast protocol, to be understood by the transponder in the field. This is w hy, the EVB90109 include a “fast decay” circuit controlled through the pin FAST_D EC AY and com posed of the transitstor Q 1 and the diode D 1. The follow ing picture show s how to im plem ent the “fast decay” system . Picture 1: Fast D ecay m odule control, (1) Antenna, (2) M O D U R 2, (3) FAST_D EC AY
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3 Schem atic
The follow ing diagram show s the schem atic of the EVB90109. All com ponents in grey are not m ounted but the footprints are present if the user w ants to use it for dedicated applications. 1 8 MLX90109 VD D VD D L C R1C1 R2 R3 C3 COIL VSS SPEED MODE CLOCK DATA VDD MODUR3 MODUR2 D1 Q1
4 Fast_Decay
Figure 2: Schem atic of the EVB90109
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4 Physical outline
The follow ing figure show s the outline of the M LX90109 evaluation board. Figure 3: EVB90109 outline: top side R2 C1 R1 C3 D1 MLX90109 Coil DIL-10 DIL-10
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5 Pinning of the EVB 90109
Pin num ber D IL-10 N am e D escription
1 C O IL O scillator O utput
2 VSS G round
3 SPEED D ata rate selection
4 FAST_D EC AY Fast decay circuit control
5 M O D U R 3 M odulation N etw ork
6 M O D U R 2 M odulation N etw ork
7 M O D E D ecoding selection
8 C LO C K C lock signal
9 D ATA D ecoded data
10 VD D Pow er Supply
Table 2: Pinning of the EVB90109
6 C om ponents
R eference Value D escription R 1 39 kohm s M odulation netw ork R 2 8.2 kohm s M odulation netw ork R 3 N ot m ounted Additional resistor for the m odulation netw ork C 1 N ot m ounted N oise cancellation capacitance C 2 N ot m ounted Additional capacitance for the m odulation netw ork C 3 N ot m ounted Additional capacitance for the m odulation netw ork C 4 22nF Tune capacitance L1 73,7uH Inductance M LX90125 Table 3: C om ponents
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7 D isclaim er
D evices sold by M elexis are covered by the w arranty and patent indem nification provisions appearing in its Term of Sale. M elexis m akes no w arranty, express, statutory, im plied, or by description regarding the inform ation set forth herein or regarding the freedom of the described devices from patent infringem ent. M elexis reserves the right to change specifications and prices at any tim e and w ithout notice. Therefore, prior to designing this product into a system , it is necessary to check w ith M elexis for current inform ation. This product is intended for use in norm al com m ercial applications. Applications requiring extended tem perature range, unusual environm ental requirem ents, or high reliability applications, such as m ilitary, m edical life- support or life-sustaining equipm ent are specifically not recom m ended w ithout additional processing by M elexis for each application. The inform ation furnished by M elexis is believed to be correct and accurate. H ow ever, M elexis shall not be liable to recipient or any third party for any dam ages, including but not lim ited to personal injury, property dam age, loss of profits, loss of use, interrupt of business or indirect, special incidental or consequential dam ages, of any kind, in connection w ith or arising out of the furnishing, perform ance or use of the technical data herein. N o obligation or liability to recipient or any third party shall arise or flow out of M elexis’ rendering of technical or other services. © 2005 M elexis N V. All rights reserved. For the latest version of this docum ent, go to our w ebsite at w w w .m elexis.com O r for additional inform ation contact M elexis D irect: Europe and Japan: All other locations: Phone: +32 1367 0495 Phone: +1 603 223 2362 E-m ail: sales_europe@ m elexis.com E-m ail: sales_usa@ m elexis.com ISO /TS 16949 and ISO 14001 C ertified