TFBS5711 VISHAY [Vishay Siliconix], TFBS5711 Datasheet - Page 7

• Manufacturer Part Number: TFBS5711
• Description: Fast Infrared Transceiver Module (MIR, 1.152 Mbit/s) for IrDA
• Manufacturer: VISHAY [Vishay Siliconix]

Recommended Circuit Diagram for
IrDA
In general Vishay transceivers are using the identical
circuit for IrDA and Remote Control operation. For
using the IrDA transceiver as an RC transmitter no
change of the operating circuit is necessary. Used
with a clean low impedance power supply the
TFBS5711 only needs an external series current lim-
iting resistor. However, depending on the entire sys-
tem design and board layout, additional external
components may be required (see figure 1).
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 and this
is supply voltage dependent, see derating curve in fig-
ure 4, to avoid too high internal power dissipation.
Vishay’s transceivers integrate a sensitive receiver
Table 1.
Recommended Application Circuit Components
Document Number 82634
Rev. 1.3, 05-Dec-03
VISHAY
Component
18560
SD
Txd
Rxd
GND
®
V
V
C1
C2
R1
R2
1
2
and Remote Control Operation
Figure 1. Recommended Application Circuit
C1
5 V supply voltage: 5.6
R1
R2
C3
using two 2.8 , 0.125 W resistors in series).
3.3 V supply voltage: 2.0
C2
Recommended Value
IRED Anode
V
Ground
SD
Txd
Rxd
cc1
0.1 F, Ceramic
47 , 0.125 W
4.7 F, 16 V
s. text 0.25 W (recommended
V
cc2
s. text 0.25 W
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 of the supply voltages V
noise. An unstable power supply with dropping volt-
age during transmission may reduce the sensitivity
(and transmission 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
low the fast current rise time. In that case another 4.7
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.
Keep in mind that basic RF - design rules for circuit
design should be taken into account. Especially
longer signal lines should not be used without termi-
nation. See e.g. "The Art of Electronics" Paul Horow-
itz, Winfield Hill, 1989, Cambridge University Press,
ISBN: 0521370957.
F (type, see table under C1) at V
2
. Often some power supplies are not apply to fol-
e.g. 2 x CRCW-1206-2R0-F-RT1 for 3.3 V supply voltage
CRCW-1206-47R0-F-RT1
VJ 1206 Y 104 J XXMT
Vishay Part Number
293D 475X9 016B
Vishay Semiconductors
TFBS5711
1
and V
2
will be helpful.
2
www.vishay.com
and injected
7