EVB90109 MLX90109 Evaluation Board Features and Benefits Minimum PCB size (30 * 30 mm) including a MLX90109 transceiver IC and an optimized antenna Tuned resonance frequency to 125kHz Modulation network on board for a maximum flexibility Setup for fast On/Off keying modulation mode DIL-10 footprint for easy mounting on prototype set up and development kit Ordering Information Part No. EVB90109 Applications Examples Evaluation Board Car Immobilizers Portable readers Battery powered door locks Access control House held appliances General Description The EVB90109 is an assembled module that allows evaluating the advantages of the MLX90109 transceiver IC. It will facilitate the starts of RFID applications and can be implemented in a compact way, with minimum development time, and minimum final system cost. All pins of the MLX90109 reader are available on a DIL socket for easy control with an external microcontroller. Two extra pins have been added for extended control options on the voltage on the MODU pin. The EVB90109 can be used as a 125 kHz reader, to read out the load modulation from a transponder. It can also be used to send information to a transponder using On/Off keying modulation. For fast protocol which required fast fall time on the reader’s antenna, the EVB90109 includes a “Fast decay” circuit composed of an external transistor and diode in parallel on the antenna. This circuit is accessible through a digital pin on the DIL-10 connector. 390129010901 Rev 005 Page 1 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board Table of Contents 1 EVB90109 ELECTRICAL SPECIFICATIONS................................................................................................................................. 3 2 DESCRIPTION ............................................................................................................................................................................. 3 2.1 GENERAL EXPLANATION .......................................................................................................................... 3 2.2 PARALLEL ANTENNA ............................................................................................................................... 4 2.3 MODULATION NETWORK .......................................................................................................................... 4 2.4 ANTENNA VOLTAGE IN READ OPERATION ................................................................................................... 4 2.5 NOISE CANCELLATION IN READ OPERATION ............................................................................................... 5 2.6 ANTENNA VOLTAGE IN 100% MODULATION OPERATION............................................................................... 5 2.7 FAST DECAY CIRCUIT .............................................................................................................................. 6 3 SCHEMATIC................................................................................................................................................................................ 7 4 PHYSICAL OUTLINE ................................................................................................................................................................... 8 5 PINNING OF THE EVB90109 ....................................................................................................................................................... 9 6 COMPONENTS............................................................................................................................................................................ 9 7 DISCLAIMER..............................................................................................................................................................................10 390129010901 Rev 005 Page 2 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 1 EVB90109 Electrical Specifications Parameter Supply Voltage Resonance frequency Condition Vdd = 5Volts Symbol Vdd Fres Min 4.5 120 Typ 5 125 Max 5.5 130 Units Volts kHz Table 1: Electrical specifications 2 Description 2.1 General explanation The EVB90109 consists of a single chip inductive RFID reader for the 125 kHz frequency range with an external inductance (L) and capacitance (C) connected as a parallel resonant circuit. The antenna voltage amplitude can be set On/Off externally with the digital line MODUR2, which controls a resistive and capacitive network called “Modulation network” connected to the MODU pin of the chip. This allows maximum reading distance and reliability, can be used to preserve energy by easily setting the evaluation board in power down mode and finally allows 100% modulation for reader talk first applications. The EVB90109 also includes a “fast decay” circuit composed of an external transistor and diode in parallel to the resonant antenna, used to short the antenna for negative swings to dissipate the remaining energy into the transistor and then, to reduce the fall time of the antenna. For more information, please refer to the application note “100% Modulation (On/Off keying)”. An additional footprint of “Modulation network” is available on the board and is accessible through the MODUR3 digital connection. All others digital connections as SPEED, MODE, MODU, CLOCK and DATA, are available on the DIL-10 connector. Parallel resonant antenna (L, C4, C5) Connector DIL-10 Modulation Network (R1, R2) MLX90109 Fast decay circuit (Q1, Figure 1: EVB90109 Note: The EVB90109 does not include any pull-up resistors on the digital connections DATA and CLOCK. This must be done externally, by configuring the IO ports of a microcontroller in pull-up mode, or by adding two external resistors connected between the digital pins and Vdd. 390129010901 Rev 005 Page 3 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 2.2 Parallel antenna The parallel antenna of the EVB90109 consists of the inductance (L) based on the MLX90125 reader coil and the tune capacitor (C4), which form a resonant system at 125 kHz with a total (inductance and capacitance) antenna impedance of about 1.3kOhms. The MLX90109 is specified to drive a minimal antenna impedance of 1kOhm, which can be theoretically calculated using the following formula. Z ant = Qant ⋅ ωres ⋅ Lr Care should be taken that the presence of a transponder may reduce the theoretical antenna impedance to be smaller that the minimum specified. Therefore it may be of interest to take some extra margin in the antenna design by taking a slightly higher quality factor to increase the antenna impedance. A tune capacitance with a poor quality factor may also reduce the global performances of the antenna, as shown in the following formula. Qant = QL // QC Therefore, the tune capacitance should be taken with a high quality factor or low ESR (plastic or mica) to not reduce the total impedance of the antenna and moreover, to not annihilate all the efforts made in the design of the antenna to work with a high quality factor and then to get the maximum of operating distance. 2.3 Modulation network The modulation network is used to set the voltage on the MODU pin of the MLX90109. As shown in the following formula, the voltage on the antenna can be adjusted according to this voltage. This features can be used to reduce the power consumption of the chip by setting a lower voltage on the antenna. Under no circumstances it can be used to make proportionnal modulaiton, due to internal feedback loop which doesn’t allow this use. Vant = V DD − VMODU − Vovershoot The EVB90109 is provided with two resistors R1 and R2 as the modulation netwok controlled through the pin MODUR2 to set the voltage on the antenna respectively On (Vmodu to 0.8 Volts) and Off (Vmodu to 5 Volts). Others footprint C1, C3 and R3 and an extra pin MODUR3 are available on the board and can be used for specific applications. 2.4 Antenna voltage in read operation The resistors R1 and R2 set VMODU to 0.8V (1V for full temperature range [–40, 85] C) which is the lowest possible voltage to guarantee that the antenna driver of the MLX90109 stays out of its linear operating zone. The field is set On (VMODU to 0.8V) and Off (VMODU to VDD) when applying 0V and VDD on pin MODUR2. 390129010901 Rev 005 Page 4 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 2.5 Noise cancellation in read operation The resonant antenna is a natural band-pass filter, which becomes more effective as Qant increases. The MLX90109 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 Manchester data spectrum: 2kbaud (speed = 1): 400Hz to 3.6kHz 4kbaud (speed = 0): 800Hz to 7.2kHz Noise that is injected on MODU pin or on VDD will cause Vant to change, and will therefore be considered to be data by the sampler. This noise can simply be cancelled by adding a capacitor C1 between MODU and VDD. Together with the modulation network R1 and R2, its creates a high pass filter with cut off frequency at: 1 2 ⋅ π ⋅ ( R1 // R2 ) ⋅ C1 Note: Due to the long time constant introduces and the parasitic oscillations that it may provoke with the transistor Q1, the capacitor C1 must be removed when using the EVB90109 in On/Off keying modulation mode. 2.6 Antenna voltage in 100% modulation operation The modulation network R1 and R2 can be used to set the voltage amplitude on the antenna On and Off by applying 0 Volts and Vdd on the pin MODUR2. Switching ON the magnetic field depends on the internal driver of MLX90109 and takes less than 5 carrier periods. Switching OFF the magnetic field depend on the quality factor (Qant) of the parallel antenna connected to the reader (about 24 periods with the EVB90109). To reduce this fall time, the “fast decay” circuit can be used. 390129010901 Rev 005 Page 5 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 2.7 Fast decay circuit Very small fall time may be required in fast protocol, to be understood by the transponder in the field. This is why, the EVB90109 include a “fast decay” circuit controlled through the pin FAST_DECAY and composed of the transitstor Q1 and the diode D1. The following picture shows how to implement the “fast decay” system. Picture 1: Fast Decay module control, (1) Antenna, (2) MODUR2, (3) FAST_DECAY 390129010901 Rev 005 Page 6 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 3 Schematic The following diagram shows the schematic of the EVB90109. All components in grey are not mounted but the footprints are present if the user wants to use it for dedicated applications. 4 Fast_Decay Q1 D1 L VDD VDD C C1 R1 1 VSS 2 2 SPEED 3 3 4 R2 R3 8 MLX90109 COIL 1 10 VDD 7 9 DATA 6 8 CLOCK 5 7 MODE C3 5 MODUR3 6 MODUR2 Figure 2: Schematic of the EVB90109 390129010901 Rev 005 Page 7 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 4 Physical outline The following figure shows the outline of the MLX90109 evaluation board. Coil DIL-10 1 C4 DIL-10 10 R1 R3 C3 2 MLX90109 C1 3 9 8 R2 D1 4 7 5 6 Q1 Figure 3: EVB90109 outline: top side 390129010901 Rev 005 Page 8 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 5 Pinning of the EVB90109 Pin number DIL-10 1 2 3 4 5 6 7 8 9 10 Name COIL VSS SPEED FAST_DECAY MODUR3 MODUR2 MODE CLOCK DATA VDD Description Oscillator Output Ground Data rate selection Fast decay circuit control Modulation Network Modulation Network Decoding selection Clock signal Decoded data Power Supply Table 2: Pinning of the EVB90109 6 Components Reference R1 R2 R3 C1 C2 C3 C4 L1 Value 39 kohms 8.2 kohms Not mounted Not mounted Not mounted Not mounted 22nF 73,7uH Description Modulation network Modulation network Additional resistor for the modulation network Noise cancellation capacitance Additional capacitance for the modulation network Additional capacitance for the modulation network Tune capacitance Inductance MLX90125 Table 3: Components 390129010901 Rev 005 Page 9 of 10 Evaluation Board Aug-2005 EVB90109 MLX90109 Evaluation Board 7 Disclaimer Devices sold by Melexis are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. Melexis makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. Melexis reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with Melexis for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical lifesupport or life-sustaining equipment are specifically not recommended without additional processing by Melexis for each application. The information furnished by Melexis is believed to be correct and accurate. However, Melexis shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interrupt of business or indirect, special incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of Melexis’ rendering of technical or other services. © 2005 Melexis NV. All rights reserved. For the latest version of this document, go to our website at www.melexis.com Or for additional information contact Melexis Direct: Europe and Japan: All other locations: Phone: +32 1367 0495 E-mail: [email protected] Phone: +1 603 223 2362 E-mail: [email protected] ISO/TS 16949 and ISO14001 Certified 390129010901 Rev 005 Page 10 of 10 Evaluation Board Aug-2005