Linear Technology DC112A Demo Manual page 4

DEMO MANUAL DC112A
OPERATIO
IrDA-SIR
Because SIR systems transmit a pulse for a zero and
nothing for a one (see Figure 3a), the two photographs
demonstrating the SIR modulation show a sequence of
zeros. In both photographs, the input data to the transmit-
ter is shown on the bottom and the output of the IR receiver
IrDA-SIR (1m)
RECEIVER
OUTPUT
TRANSMITTER
INPUT
4
Arrow.com. Arrow.com. Arrow.com. Arrow.com.
Downloaded from Downloaded from Downloaded from Downloaded from
U
0 1
DATA RATES: 2400BAUD TO 115kBAUD
BIT INTERVAL: 417µs TO 8.7µs
PULSE WIDTH: 3/16 OF INTERVAL OR 1.63µs
3b
is shown on the top. Note that the receiver output is a TTL
LOW for a transmitted light pulse. The two photos, Figures
3b and 3c, show received data at 1 meter and 1cm. There
is not much difference at distances in between.
0 0 1 1 0 1
3a
IrDA-SIR (1cm)
RECEIVER
OUTPUT
TRANSMITTER
INPUT
Figure 3. IrDA-SIR Modulation
NRZ DATA
0
IrDA-SIR HIGH = LIGHT TRANSMITTED
1328 F02a
3c