MAX220–MAX249
+5V-Powered, Multichannel
RS-232 Drivers/Receivers
Test Circuits/Timing Diagrams
+3V
0V*
+3V
INPUT
0V
OUTPUT
V+
OUTPUT
0V
V-
t
PHLR
t
PHLS
V
CC
50%
50%
GND
t
PLHR
t
PLHS
INPUT
50%
50%
t
PLHT
t
PHLT
*EXCEPT FOR R2 ON THE MAX243
WHERE -3V IS USED.
Figure 1. Transmitter Propagation-Delay Timing
Figure 2. Receiver Propagation-Delay Timing
EN
R
X
OUT
R
X
IN
a) TEST CIRCUIT
150pF
EN INPUT
+3V
0V
V+
EN
OUTPUT ENABLE TIME (t
ER
)
+3.5V
RECEIVER
OUTPUTS
+0.8V
a) TIMING DIAGRAM
b) ENABLE TIMING
+3V
EN INPUT
V
OH
RECEIVER
OUTPUTS
V
OL
c) DISABLE TIMING
V
OL
+ 0.5V
0V
OUTPUT DISABLE TIME (t
DR
)
V
OH
- 0.5V
V
CC
- 2V
b) TEST CIRCUIT
EN
1 OR 0
T
X
3kΩ
50pF
V-
+5V
0V
-5V
OUTPUT DISABLE TIME (t
DT
)
R
X
1kΩ
V
CC
- 2V
SHDN
+3V
0V
Figure 3. Receiver-Output Enable and Disable Timing
Figure 4. Transmitter-Output Disable Timing
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