EVB90109
MLX90109 Evaluation Board
390129010901 Page 1 of 10 Evaluation Board
Rev 005 Aug-2005
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.
EVB90109
MLX90109 Evaluation Board
390129010901 Page 2 of 10 Evaluation Board
Rev 005 Aug-2005
Table of Contents
1 EVB90109 ELECTRICAL SPECIFICATIONS................................................................................................................................. 3
2 DESCRIPTION............................................................................................................................................................................. 3
2.1
G
ENERAL EXPLANATION
.......................................................................................................................... 3
2.2
P
ARALLEL ANTENNA
...............................................................................................................................4
2.3
M
ODULATION NETWORK
.......................................................................................................................... 4
2.4
A
NTENNA VOLTAGE IN READ OPERATION
................................................................................................... 4
2.5
N
OISE CANCELLATION IN READ OPERATION
...............................................................................................5
2.6
A
NTENNA VOLTAGE IN
100%
MODULATION OPERATION
............................................................................... 5
2.7
F
AST DECAY CIRCUIT
..............................................................................................................................6
3 SCHEMATIC................................................................................................................................................................................ 7
4 PHYSICAL OUTLINE ................................................................................................................................................................... 8
5 PINNING OF THE EVB90109 ....................................................................................................................................................... 9
6 COMPONENTS............................................................................................................................................................................ 9
7 DISCLAIMER..............................................................................................................................................................................10
EVB90109
MLX90109 Evaluation Board
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Rev 005 Aug-2005
1 EVB90109 Electrical Specifications
Parameter Condition Symbol Min Typ Max Units
Supply Voltage
Vdd
4.5
5
5.5
Volts
Resonance frequency Vdd = 5Volts Fres 120 125 130 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.
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.
Parallel
na (L
, C4, C5
)
Fast decay circuit (Q1
,
MLX90109
Modulation Network (R1
, R2
)
Connector DIL
-
10
EVB90109
MLX90109 Evaluation Board
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Rev 005 Aug-2005
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.
rresantant
LQZ ⋅⋅=
ω
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.
CLant
QQQ //=
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.
overshootMODUDDant
VVVV −−=
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.
EVB90109
MLX90109 Evaluation Board
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Rev 005 Aug-2005
2.5 Noise cancellation in read operation
The resonant antenna is a natural band-pass filter, which becomes more effective as Q
ant
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:
( )
121
//2 1CRR ⋅⋅⋅
π
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.
EVB90109
MLX90109 Evaluation Board
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Rev 005 Aug-2005
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
EVB90109
MLX90109 Evaluation Board
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Rev 005 Aug-2005
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.
1 8
7
6
5
2
3
4
MLX90109
VDD
VDD
L
C
R1
C1
R2 R3 C3
COIL
VSS
SPEED
MODE
CLOCK
DATA
VDD
MODUR3
MODUR2
1
2
3
5
6
7
8
9
10
D1 Q1
4
Fast_Decay
Figure 2: Schematic of the EVB90109
EVB90109
MLX90109 Evaluation Board
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Rev 005 Aug-2005
4 Physical outline
The following figure shows the outline of the MLX90109 evaluation board.
Figure 3: EVB90109 outline: top side
R2
C1
R1
R3
C3 D1
C4
Q
1
MLX90109
Coil
DIL
-
10
DIL
-
10
1
2
3
4
5
10
9
8
7
6
EVB90109
MLX90109 Evaluation Board
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Rev 005 Aug-2005
5 Pinning of the EVB90109
Pin number DIL-10 Name Description
1 COIL Oscillator Output
2 VSS Ground
3 SPEED Data rate selection
4 FAST_DECAY Fast decay circuit control
5 MODUR3 Modulation Network
6 MODUR2 Modulation Network
7 MODE Decoding selection
8 CLOCK Clock signal
9 DATA Decoded data
10 VDD Power Supply
Table 2: Pinning of the EVB90109
6 Components
Reference Value Description
R1 39 kohms Modulation network
R2 8.2 kohms Modulation network
R3 Not mounted Additional resistor for the modulation network
C1 Not mounted Noise cancellation capacitance
C2 Not mounted Additional capacitance for the modulation network
C3 Not mounted Additional capacitance for the modulation network
C4 22nF Tune capacitance
L1 73,7uH Inductance MLX90125
Table 3: Components
EVB90109
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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 life-
support 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 Phone: +1 603 223 2362
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