TFDU7100-TR3 VISHAY [Vishay Siliconix], TFDU7100-TR3 Datasheet - Page 7

• Manufacturer Part Number: TFDU7100-TR3
• Description: Infrared Transceiver Module (FIR, 4 Mbit/s) for IrDA combined with Remote Control Receiver (36 kHz to 38 kHz Carrier)
• Manufacturer: VISHAY [Vishay Siliconix]

Recommended Circuit Diagram
Operated at a clean low impedance power supply the
TFDU7100 needs no additional external components
beside a resistor at the open collector RC-RXD-out-
put. However, depending on the entire system design
and board layout, additional components may be
required (see figure 2).
The capacitor C1 is buffering the supply voltage and
eliminates the inductance of the power supply line.
This one should be a Tantalum or other fast capacitor
to guarantee the fast rise time of the IRED current.
The resistor R1 is the current limiting resistor, which
may be used to reduce the operating current to levels
below the specified controlled values for saving bat-
tery power.
Vishay’s transceivers integrate a sensitive receiver
and a built-in power driver. The combination of both
needs a careful circuit board layout. The use of thin,
long, resistive and inductive wiring should be avoided.
The inputs (TXD, SD) and the output RXD should be
directly (DC) coupled to the I/O circuit.
The capacitor C2 combined with the resistor R2 is the
low pass filter for smoothing the supply voltage. R2,
C1 and C2 are optional and dependent on the quality
Recommended Application Circuit Components
Document Number 84773
Rev. 1.1, 27-Sep-06
Component
RXD
V
V
GND
RC-RXD
SD
TXD
CC
IRED
19600
C1
C2
R1
R2
R3
Figure 2. Recommended Application Circuit
C1
R3
R1
R2
depends on current to be adjusted
C2
Recommended Value
0.1 µF, Ceramic
10 kΩ, 0.125 W
47 Ω, 0.125 W
4.7 µF, 16 V
IRED Anode
V
Ground
RC-RXD
SD
TXD
RXD
IRED Cathode
CC1
of the supply voltages V
unstable power supply with dropping voltage during
transmission may reduce the sensitivity (and trans-
mission range) of the transceiver.
The placement of these parts is critical. It is strongly
recommended to position C2 as close as possible to
the transceiver power supply pins. An Tantalum
capacitor should be used for C1 while a ceramic
capacitor is used for C2.
In addition, when connecting the described circuit to
the power supply, low impedance wiring should be
used.
When extended wiring is used the inductance of the
power supply can cause dynamically a voltage drop
at V
follow the fast current rise time. In that case another
4.7 µF (type, see table under C1) at V
ful.
The RC-RXD output is an open collector driver.
Therefore it needs an external pull-up resistor of e.g.
10 kΩ (R3).
Under extreme EMI conditions as placing an RF-
transmitter antenna on top of the transceiver, we rec-
ommend to protect all inputs by a low-pass filter, as a
minimum a 12 pF capacitor, especially at the RXD
port. The transceiver itself withstands EMI at GSM
frequencies above 500 V/m. When interference is
observed, it is picked up by the wiring to the inputs. It
is verified by DPI measurements that as long as the
interfering RF - voltage is below the logic threshold
levels of the inputs and equivalent levels at the out-
puts no interference is expected.
One should keep in mind that basic RF - design rules
for circuit design should be taken into account. Espe-
cially longer signal lines should not be used without
termination. See e.g. "The Art of Electronics" Paul
Horowitz, Winfield Hill, 1989, Cambridge University
Press, ISBN: 0521370957.
CC2
. Often some power supplies are not apply to
VJ 1206 Y 104 J XXMT
Vishay Part Number
293D 475X9 016B
CRCW-0805-47R
CRCW-0805-10K
Vishay Semiconductors
CCx
and injected noise. An
TFDU7100
CC2
www.vishay.com
will be help-
7