Datasheet

Keep communications cables short to minimize capaci-
tive loading. Lowering the capacitive loading on the
transmitter outputs reduces the MAX3218’s power con-
sumption. Using short, low-capacitance cable also
helps transmission at the highest data rates.
EIA/TIA-232E and
_____________EIA/TIA-562 Standards
RS-232 circuits consume much of their power because
the EIA/TIA-232E standard demands that the transmit-
ters deliver at least 5V to receivers with impedances
that can be as low as 3k Ω. For applications where
power consumption is critical, the EIA/TIA-562 standard
provides an alternative.
EIA/TIA-562 transmitter output voltage levels need only
reach ±3.7V, and because they have to drive the same
3kΩ receiver loads, the total power consumption is con-
siderably reduced. Since the EIA/TIA-232E and
EIA/TIA-562 receiver input voltage thresholds are the
same, interoperability between EIA/TIA-232E and
EIA/TIA-562 devices is guaranteed. Maxim’s MAX560
and MAX561 are EIA/TIA-562 transceivers that operate
on a single supply from 3.0V to 3.6V, and the MAX562
transceiver operates from 2.7V to 5.25V while produc-
ing EIA/TIA-562 levels.
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
_______________________________________________________________________________________ 9
TRANSMITTERS ENABLED, INVALID HIGH
AUTOSHUTDOWN, TRANSMITTERS DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
TRANSMITTERS ENABLED, INVALID HIGH
-2.8V
-0.3V
+2.8V
AUTOSHUTDOWN RECEIVER INPUT THRESHOLD (V)
+0.3V
(a)
(b)
0V
INDETERMINATE
INDETERMINATE
V-
V
CC
0V
V+
0
V
CC
t
INVL
t
WU
INVALID
REGION
RECEIVER
INPUT
VOLTAGE
(V)
INVALID
OUTPUT
(V)
t
INVH
Figure 4. AutoShutdown Trip Levels
Figure 5. AutoShutdown with Initial Turn-On to Wake Up a
System
FORCEON
MASTER SHDN LINE
0.1µF 1M
FORCEOFF
MAX3218
POWER
MANAGEMENT
UNIT