EM4022
Typical Operating Configurations
Medium frequency applications are those which cannot
use the integrated full wave rectifier and where the
transponder power is transmitted through a coil. External
microwave schottky diodes are required to rectify the
carrier wave. An external power storage capacitor can be
added to improve reading range.
Low frequency inductive transponder .
VDD
M
These applications allow higher data rates (64 kbit/s).
Where reading rates of 500 transponders per second
can be achieved
CPX
Coil1
L
EM4022
High frequency RF transponder implementation.
Coil2
GAP
VSS
VDD
M
Coil1
CPX
D1
D3
Fig. 2
EM4022
Low frequency applications are those applications that
can make use of the on-chip full wave rectifier bridge to
rectify the incident energy. These are typically
applications that use inductive coupling to transmit
energy to the chip. The carrier frequency is typically less
than 500 kHz. The design of the on-chip rectifier and
resonance capacitor is optimized for frequencies in the
order of 125 kHz. Low frequency transponders can be
implemented using just a EM4022 chip and an external
coil that resonates with the on-chip tuning capacitor at
the required carrier frequency. An external power
storage capacitor is required to maintain the supply
voltage above the integrated power on reset level.
In a very strong field, due to the forward resistance of the
diode, the GAP input must be limited at VSS-0.3V by a
schottky diode (D1)
D2*
D1
Coil2
GAP
VSS
Fig. 4
D2 in figure 2 and 3 is optional and is only used for GAP
enable versions. All diodes are schottky type.
High frequency applications are similar to medium
frequency applications. These are typically applications
that use electromagnetic RF coupling to transmit energy
to the chip using carrier frequencies greater than
100 MHz. High frequency transponders can be
implemented using a EM4022 chip, two or three
microwave diodes and a printed antenna. High frequency
RF coupled applications typically have higher reading
distances (> 4 m) and
Medium frequency (13.56 MHz) inductive transponder
implementation
VDD
M
Bi-frequency applications are possible by implementing
a coil between coil1 and coil2 connections in the high
frequency application (fig. 4).
CPX
EM4022
C
L
D2*
GAP
VSS
D1
Fig. 3
L:
coil antenna (typical value 1.35 µH).
tuning capacitor (typical value 100 pF)
C:
2
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