LTC1348 LINER [Linear Technology], LTC1348 Datasheet - Page 7

• Manufacturer Part Number: LTC1348
• Description: 3.3V/5V Low Power RS232 3-Driver/5-Receiver Transceiver
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
High Data Rates
The LTC1348 maintains true RS232 5V minimum driver
output even at high data rates. Figure 5 shows a test circuit
with 2m wires connecting the two test chips. Both chips
are run from 3.3V supplies. Figure 6 shows the typical line
waveforms with all three drivers, loaded with 1000pF and
3k , toggling simultaneously at 120kbaud. Figure 7 shows
0.1 F
0.1 F
1000pF
1000pF
1000pF
0.1 F
0.1 F
0.1 F
0.1 F
DR1 OUT
Figure 5. Data Rate Evaluation Circuit
DR2 OUT
DR3 OUT
DR1 OUT
DR2 OUT
DR3 OUT
RX1 IN
RX2 IN
RX3 IN
RX4 IN
RX5 IN
RX1 IN
RX2 IN
RX3 IN
RX4 IN
RX5 IN
V
V
V
V
+
+
CC
CC
C2
C2
C1
C2
C1
C1
C2
C1
U
+
–
+
+
+
–
–
–
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12
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12
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INFORMATION
U
LTC1348
LTC1348
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
W
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C3
C3
C3
C3
DR1 IN
RX1 OUT
DR2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DR3 IN
RX5 OUT
DREN
RXEN
GND
DRIVER 1 IN
RX1 OUT
DRIVER 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DRIVER 3 IN
RX5 OUT
DREN
RXEN
GND
+
–
+
–
LT1348 • F05
V
V
–
–
0.1 F
0.1 F
U
0.1 F
0.1 F
the same circuit with a single 1000pF/3k loaded driver
driven at 250kbaud, and the other two drivers loaded but
not toggling. This closely approximates the actual behav-
ior of an RS232 serial port, with only one driver (TX) driven
at high speed and the other two drivers (RTS and DTR)
driven at a relatively low data rate or at DC. Under the same
conditions, the LTC1348 can go as fast as 350kbaud and
still meet EIA562 ( 3.7V) minimum driver output levels.
RECEIVER OUTPUT
RECEIVER OUTPUT
DRIVER OUTPUT
DRIVER OUTPUT
DRIVER INPUT
DRIVER INPUT
Figure 7. Driver Test Results at 250kbps
Figure 6. Driver Test Result at 120kbps
LTC1348
LTC1348 G06
LTC1348 G07
7