Datasheet

MAX3250
±50V Isolated, 3.0V to 5.5V,
250kbps, 2 TX/2 RX, RS-232 Transceiver
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Detailed Description
The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated
EIA/TIA-232 and V.28/V.24 communications interface
with high data-rate capabilities. The MAX3250 is a dual
die part that operates with up to ±50V difference
between the RS-232 side and the logic side (ISOCOM
to GND). This makes the device ideal for operation in
noisy conditions with high common-mode voltages.
This feature prevents damage to the device if RS-232
lines are inadvertently short-circuited to a +24V or ±48V
power bus.
The MAX3250 typically draws 15mA of supply current
when unloaded. Supply current drops to 20µA when
the device is placed in shutdown mode.
The MAX3250 has two receivers and two drivers and is
guaranteed to operate at data rates up to 250kbps. The
device features a FAULT open-drain output to signal an
excessive isolated-side voltage condition on any of the
RS-232 inputs. This output can drive an alarm LED or can
be monitored by the processor to prevent operation
under these conditions. The receiver outputs are high
impedance in shutdown, allowing multiple interfaces
(IrDA, RS-232, RS-485) to be connected to the same
UART (Figure 1). The MAX3250 is a low-cost replacement
for opto-isolated transceivers.
Isolated Power Supply
The MAX3250 drives a high-frequency square wave into
C1 and a complementary square wave into C2. These
POWER
CONTROLLER
FAULT
SHDN
GND C1- C2- C1+ C2+ ISOCOM
TOUT2
RIN2
ISOVCC
C3+
C3-
C4+
C4-
V+
V-
TIN1
ROUT1
ROUT2
TIN2
TOUT1
RIN1
RS-232
CHARGE
PUMP
V
CC
MAX3250
FAULT
DETECTOR
OSC
Figure 1. Functional Diagram