MC33690 Datasheet, PDF (5/24 Pages) Motorola, Inc – Standalone Tag Reader Circuit

Freescale S^Me^Cm³³i⁶c⁹o⁰nductor, Inc.
DESCRIPTION
TAG READER MODULE
The Tag Reader module is dedicated for
automotive or industrial applications where
information has to be transmitted contactless.
The tag reader module is a write/read (challenge/
response) controller for applications which
demand high security level.
The tag reader module is connected to a serial
tuned LC circuit which generates a magnetic field
power supplying the tag.
The use of a synchronous sample & hold
technique allows communication with all
avalaible tags using admittance switching
producing absorption of the RF field.
Load amplitude or phase shift modulation can be
detected at high bit rates up to 8kHz.
125kHz is the typical operational carrier
frequency of the tag reader module with a 8MHz
clock.
Figure 2 : Tag Reader block diagram
R_A
TD1
L_A
1/32 counter
1/2
125kHz
4MHz
8MHz
AM Data
Clock 8MHz
125kHz
Self synchronous
C_A
sample & hold
TD2
Setup & Preload
R₁
RD
R₂
11.25° , 22.5° , 33.75° , 45° , 56.25° , 67.5° , 78.75° , 90°
+ 0°, -11.25°, -22.5°, -33.75°, -45°, -56.25°, -67.5°, -78.75°
VDD
Buffer
500ns
S/H
+
-
Buffer
Comparator
+
100KΩ
-
VDD
500µA
DQ
C
Shutdown
LVR
Interface
Data out
AGND
C_EXT
CEXT
10nF
© Motorola, Inc., 2002.
F^Mo^Or ^TM^Oo^Rr^Oe^LAIn^Sfo^EMrm^ICa^Ot^Nio^Dn^UCO^Tn^ORT^Sh^Pis^ROP^Dro^Ud^Cu^TSct,
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revision 4.8, 5 February 2002