_______________Detailed Description

Dual Charge-Pump Voltage Converter

The MAX3222E/MAX3232E/MAX3237E/MAX3241E’s

internal power supply consists of a regulated dual

charge pump that provides output voltages of +5.5V

(doubling charge pump) and -5.5V (inverting 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).

RS-232 Transmitters

The transmitters are inverting level translators that con-

vert TTL/CMOS-logic levels to ±5.0V EIA/TIA-232-com-

pliant levels.

The MAX3222E/MAX3232E/MAX3237E/MAX3241E

transmitters guarantee a 250kbps data rate with worst-

case loads of 3k

Ω in parallel with 1000pF, providing

compatibility with PC-to-PC communication software

(such as LapLink™). Transmitters can be paralleled to

drive multiple receivers or mice.

The MAX3222E/MAX3237E/MAX3241E’s transmitters are

disabled and the outputs are forced into a high-imped-

ance state when the device is in shutdown mode (SHDN =

GND). The MAX3222E/MAX3232E/MAX3237E/MAX3241E

permit the outputs to be driven up to ±12V in shutdown.

The MAX3222E/MAX3232E/MAX3241E transmitter

inputs do not have pull-up resistors. Connect unused

inputs to GND or VCC. The MAX3237E transmitter

inputs have a 400k

Ω 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

guarantee a 1Mbps data rate with worst-case loads of

3k

±10% operation, the MAX3237E transmitters guarantee a

1Mbps data rate into worst-case loads of 3k

Ω in parallel

with 1000pF.

RS-232 Receivers

The receivers convert RS-232 signals to CMOS-logic

output levels. The MAX3222E/MAX3237E/MAX3241E

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 shut-

down (Table 1).

±15kV ESD-Protected, Down to 10nA, 3.0V to 5.5V,

Up to 1Mbps, True RS-232 Transceivers

_______________________________________________________________________________________

7

_________________________________________________Pin Description (continued)

No Connection

N.C.

—

MegaBaud Control Input. Connect to

GND for normal operation; connect to

MBAUD

15*

Noninverting Complementary

Receiver Outputs. Always active.

R_OUTB

16

Shutdown Control. Active low.

SHDN

14*

+3.0V to +5.5V Supply Voltage

26

FUNCTION

NAME

MAX3237E

11, 14

—

—

—

—

—

20

18

19

17

TSSOP/

SSOP

SO/DIP

MAX3222E

1, 10, 11,

20

—

—

—

—

—

—

—

19

16

TSSOP/

SSOP

SO/DIP

MAX3232E

—

—

20, 21

22

26

PIN

MAX3241E

*These pins have an active positive feedback resistor internal to the MAX3237E, allowing unused inputs to be left unconnected.

LapLink is a trademark of Traveling Software.