TFBS6712 Vishay, TFBS6712 Datasheet - Page 8

• Manufacturer Part Number: TFBS6712
• Description: Low Profile Fast Infrared Transceiver Fir, 4 Mbit/s For Irda Applications With Low Voltage Logic 1.8 V
• Manufacturer: Vishay

Mode Switching
The TFBS6712 is in the SIR mode after power on as
a default mode, therefore the FIR data transfer rate
has to be set by a programming sequence using the
TXD and SD inputs as described below. The low fre-
quency mode covers speeds up to 115.2 kbit/s. Sig-
nals with higher data rates should be detected in the
high frequency mode. Lower frequency data can also
be received in the high frequency mode but with
reduced sensitivity. To switch the transceivers from
low frequency mode to the high frequency mode and
vice versa, the programming sequences described
below are required.
Setting to the High Bandwidth Mode
(0.576 Mbit/s to 4 Mbit/s)
1. Set SD input to logic "HIGH".
2. Set TXD input to logic "HIGH". Wait t
3. Set SD to logic "LOW" (this negative edge latches
state of TXD, which determines speed setting).
4. After waiting t
“LOW”. The hold time of TXD is limited by the maxi-
mum allowed pulse length.
TXD is now enabled as normal TXD input for the high
bandwidth mode.
Truth table
Document Number 84674
Rev. 1.2, 21-Feb-07
high
low
low
low
low
low
SD
h
t 200 ns TXD can be set to logic
high > 80µs
TXD
high
low
low
low
x
Inputs
Optical input Irradiance [mW/m
s
t 200 ns.
< Max. irradiance E
> Max. irradiance E
> Min. irradiance E
in angular range
in angular range
in angular range
< 4
x
x
x
Setting to the Lower Bandwidth Mode
(2.4 kbit/s to 115.2 kbit/s)
1. Set SD input to logic "HIGH".
2. Set TXD input to logic "LOW". Wait t
3. Set SD to logic "LOW" (this negative edge latches
state of TXD, which determines speed setting).
4. TXD must be held for t
TXD is now enabled as normal TXDinput for the lower
bandwidth mode.
e
SD
TXD
e
e
2
]
Figure 4. Mode Switching Timing Diagram
50 %
low active (echo)
weakly pulled
low (active)
t
(500 k:)
s
Vishay Semiconductors
RXD
high
high
high
x
h
50 %
t 200 ns.
t
h
Outputs
50 %
TFBS6712
High: FIR
Low: SIR
s
www.vishay.com
t 200 ns.
Transmitter
I
0
0
0
0
0
e
14873
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