Datasheet

TFBS4711
www.vishay.com
Vishay Semiconductors
Rev. 3.1, 03-Jul-2018
6
Document Number: 82633
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Storage
The storage and drying processes for all Vishay transceivers
(TFDUxxxx and TFBSxxx) are equivalent to MSL4.
The data for the drying procedure is given on labels on the
packing and also in the application note “Taping, Labeling,
Storage and Packing”.
Fig. 2 - Solder Profile, RSS Recommendation
RECOMMENDED CIRCUIT DIAGRAM
Operated with a clean low impedance power supply the
TFBS4711 needs no additional external components.
However, depending on the entire system design and board
layout, additional components may be required (see figure
1).
Fig. 3 - Recommended Application Circuit
Note
*)
R1 is optional when reduced intensity is used
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 battery 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 shutdown input
must be grounded for normal operation, also when the
shutdown function is not used.
The inputs (TXD, SD) and the output RXD should be directly
connected (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
CC1
and injected noise. An unstable power supply with dropping
voltage during transmision 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 pins.
When extended wiring is used as in bench tests the
inductance of the power supply can cause dynamically a
voltage drop at V
CC2
. Often some power supplies are not
able to follow the fast current rise time. In that case another
4.7 μF (type, see table under C1) at V
CC2
will be helpful.
Under extreme EMI conditions as placing an
RF-transmitter antenna on top of the transceiver, we
recommend 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, the wiring to the
inputs picks it up. 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
outputs no interferences are expected.
One should keep in mind that basic RF - design rules for
circuits design should be taken into account. Especially
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.
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
0 50 100 150 200 250 300 350
Time (s)
Temperature (°C)
20 s
2 °C...4 °C/s
2 °C...4 °C/s
90 s...120 s
T
≥
217 °C for 50 s max
T
peak
= 260 °C max.
50 s max.
T
≥
255 °C for 20 s max
19261
19295-2
V
IRED
V
CC
GND
SD
TXD
RXD
V
CC2
, IRED A
V
CC1
Ground
SD
TXD
RXD
R2
R1
(1)
C1
C2
TABLE 1 - RECOMMENDED APPLICATION
CIRCUIT COMPONENTS
COMPONEN
T
RECOMMENDED
VALUE
VISHAY PART NUMBER
C1 4.7 μF, 16 V 293D 475X9 016B
C2 0.1 μF, ceramic VJ 1206 Y 104 J XXMT
R1
Depends on current
to be adjusted
R2 47 Ω, 0.125 W CRCW-1206-47R0-F-RT1