+3V to +5.5V RS-232 Transceivers
with AutoShutdown
MAX3221/MAX3223/MAX3243
Table 3. Required Capacitor Values
V
CC
V
(V)
C1
(µF)
C2, C3, C4
(µF)
CC
0.1μF
3.0 to 3.6
4.5 to 5.5
3.0 to 5.5
0.1
0.047
0.1
0.1
V
CC
0.33
0.47
C1+
V+
V-
C3
C4
C1
C1-
C2+
MAX3221
MAX3223
MAX3243
Table 4. Logic Family Compatibility with
Various Supply Voltages
C2
C2-
SYSTEM
POWER-
SUPPLY
VOLTAGE
(V)
V
SUPPLY
VOLTAGE
(V)
CC
T_ OUT
T_ IN
COMPATIBILITY
R_ IN
R_ OUT
Compatible with all CMOS
families.
3.3
5
3.3
5
EN (MAX3221/3)
FORCEOFF
5kΩ
0V
1000pF
Compatible with all TTL and
CMOS-logic families.
V
CC
GND
Compatible with ACT and
HCT CMOS, and with TTL.
Incompatible with AC, HC,
or CD4000 CMOS.
5
3.3
Figure 8. Loopback Test Circuit
5V/div
T1IN
5V/div
T1IN
5V/div
5V/div
T1OUT
R1OUT
5V/div
5V/div
T1OUT
R1OUT
5μs/div
2μs/div
V
CC
= +3.3V, 120kbps
V
CC
= +3.3V, 235kbps
C1–C4 = 0.1μF
C1–C4 = 0.1μF
Figure 9. Loopback Test Result at 120kbps
Figure 10. Loopback Test Result at 235kbps
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