±15kV ESD-Protected, Down to 10nA, 3.0V to 5.5V,
Up to 1Mbps, True RS-232 Transceivers
MAX3222E/MAX3232E/MAX3237E/MAX3241E
†
/MAX3246E
V
CC
0.1µF
V
CC
V
CC
0.1µF
V
CC
C1+
C1
C1-
C2+
C2
C2-
T_ IN
V+
C3
C1
C1+
C1-
V+
C3
MAX3222E
MAX3232E
MAX3237E
MAX3241E
MAX3246E
V-
C4
T_ OUT
C2
C2+
C2-
T_ IN
MAX3222E
MAX3232E
MAX3237E
MAX3241E
MAX3246E
V-
C4
T_ OUT
R_ OUT
R_ IN
R_ OUT
R_ IN
5kΩ
GND
3kΩ
1000pF
(2500pF, MAX3237E only)
GND
5kΩ
7kΩ
150pF
MINIMUM SLEW-RATE TEST CIRCUIT
MAXIMUM SLEW-RATE TEST CIRCUIT
Figure 1. Slew-Rate Test Circuits
Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3222E/MAX3232E/MAX3237E/MAX3241E/
MAX3246Es’ internal power supply consists of a regu-
lated dual charge pump that provides output voltages
of +5.5V (doubling charge pump) and -5.5V (inverting
charge pump) over the +3.0V to +5.5V V
CC
range. The
charge pump operates in discontinuous mode; if the
output voltages are less than 5.5V, the charge pump is
enabled, and if the output voltages exceed 5.5V, the
charge pump is disabled. Each charge pump requires
a flying capacitor (C1, C2) and a reservoir capacitor
(C3, C4) to generate the V+ and V- supplies (Figure 1).
into a high-impedance state when the device is in shut-
down mode (SHDN = GND). The MAX3222E/
MAX3232E/MAX3237E/MAX3241E/MAX3246E permit
the outputs to be driven up to ±12V in shutdown.
The MAX3222E/MAX3232E/MAX3241E/MAX3246E
transmitter inputs do not have pullup resistors. Connect
unused inputs to GND or V
CC
. The MAX3237E’s trans-
mitter inputs have a 400kΩ active positive-feedback
resistor, allowing unused inputs to be left unconnected.
MAX3237E MegaBaud Operation
For higher-speed serial communications, the
MAX3237E features MegaBaud operation. In
MegaBaud operating mode (MBAUD = V
CC
), the
MAX3237E transmitters guarantee a 1Mbps data rate
with worst-case loads of 3kΩ in parallel with 250pF for
+3.0V < V
CC
< +4.5V. For +5V ±10% operation, the
MAX3237E transmitters guarantee a 1Mbps data rate
into worst-case loads of 3kΩ in parallel with 1000pF.
RS-232 Transmitters
The transmitters are inverting level translators that con-
vert TTL/CMOS-logic levels to ±5V EIA/TIA-232-compli-
ant levels.
The MAX3222E/MAX3232E/MAX3237E/MAX3241E/
MAX3246E transmitters guarantee a 250kbps data rate
with worst-case loads of 3kΩ in parallel with 1000pF,
providing compatibility with PC-to-PC communication
software (such as LapLink™). Transmitters can be par-
alleled to drive multiple receivers or mice.
The MAX3222E/MAX3237E/MAX3241E/MAX3246E
transmitters are disabled and the outputs are forced
LapLink is a trademark of Traveling Software.
8
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic
output levels. The MAX3222E/MAX3237E/MAX3241E/
MAX3246E receivers have inverting three-state outputs.
Drive
EN
high to place the receiver(s) into a high-
impedance state. Receivers can be either active or
inactive in shutdown (Table 1).
______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
