+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
MAX3238
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capaci-
tors with a larger nominal value. The capacitor’s equiv-
alent series resistance (ESR), which usually rises at low
temperatures, influences the amount of ripple on V+
and V-.
INVALID HIGH
+2.7V
RECEIVER INPUT LEVELS
INDETERMINATE
+0.3V
0V
-0.3V
INDETERMINATE
-2.7V
INVALID HIGH
INVALID LOW
Table 3. Required Minimum Capacitance
Values
V
CC
(V)
3.0 to 3.6
3.15 to 3.6
4.5 to 5.5
3.0 to 5.5
C1
(µF)
0.22
0.1
0.047
0.22
C2, C3, C4, C
BYPASS
(µF)
0.22
0.1
0.33
1
Figure 4a. Receiver Positive/Negative Thresholds for
INVALID
INVALID
REGION
RECEIVER
INPUTS
VOLTAGE
TRANSMITTER
INPUTS
VOLTAGE
TRANSMITTER
OUTPUTS
VOLTAGE
INVALID
OUTPUT
V
CC
0
V+
V
CC
0
V-
* ALL RECEIVERS/TRANSMITTERS INACTIVE
** ANY ONE RECEIVER/TRANSMITTER BECOMES ACTIVE
I
NVL
t
AUTOSHDN
t
AUTOSHDN
t
WU
t
WU
*
**
FORCEON = GND, FORCEOFF = V
CC
Figure 4b. AutoShutdown Plus and
INVALID
Timing Diagram
8
_______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
