CF45538NSRG4 Datasheet, PDF (14/19 Pages) Texas Instruments – TIRIS RF-Module IC for Automotive

Typical Receiver Circuit Configuration
RI45538NS
GND
VCC
7
TXLO
8
TXHI
To receiving circuit
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LC resonance circuit
T1
R1
L1
134.2KHz
Antenna
T2
C1
In this circuit configuration, by selecting a value for R1 within a range of several hundred ohms and in
accordance with the characteristics of MOSFETs (T1 and T2) and introducing the selected value, the
through current which is consumed by the MOSFETs themselves during transmission can be reduced. If
the value for R1 is too high, the on-state resistances of T1 and T2 become very high and they will have
difficulty in driving the LC resonance circuit, leading to a possible reduction of available data
communication distance. Therefore, it is recommended that the value for R1 be defined after careful
evaluation of the characteristics of T1 and T2.
L1 and C1 in the LC resonance circuit may be mutually exchanged in position without giving significant
adverse effects to the operating performance of the circuit. However, the connection as is as illustrated
above is most preferable since it reduces potential influence of high-voltage transmission signals produced
at C1 on T1 and T2, thus a higher efficiency is gained.
12 Typical Receiver Circuit Configuration
Three simple CMOS inverter type amplifiers are integrated in this RF-module IC in order to amplify the
FSK signals received from a remote TIRIS transponder up to a satisfactory logic level. The IC is designed
so as to permit their amplification factor and frequency characteristics to be selected within a certain range
by the use of appropriate external parts and/or circuits. A typical applied receiver circuit is illustrated
below.
14
TIRIS RF-Module IC for Automotive
SCBU036 – December 1996
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