±15kV ESD-Protected, 2.5V, 1µA, 460kbps,

RS-232 Compatible Transceivers

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7

Pin Description (continued)

Detailed Description

Dual Charge-Pump Voltage Converter

The MAX3316E–MAX3319Es’ internal power supply

consists of a regulated dual charge pump that provides

output voltages of +4.4V (doubling charge pump) and

-4.3V (inverting charge pump), over the +2.25V to

+3.0V range. The charge pump operates in discontinu-

ous mode: if the output voltages are less than 4.4V, the

charge pump is enabled; if the output voltages exceed

4.4V, 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.

The READY output (MAX3318E/MAX3319E) is low

when the charge pumps are disabled in shutdown

mode. The READY signal asserts high when V- goes

below -2.75V.

RS-232 Compatible Transmitters

The MAX3316E–MAX3319Es’ transmitters are inverting

level translators that convert CMOS-logic levels to

RS-232 compatible voltage levels. They guarantee a

460kbps data rate with worst-case loads of 3k

Ω in parallel

with 1000pF, providing compatibility with PC-to-PC

communication software (such as LapLink™).

The MAX3317E’s transmitters are turned off (high

impedance) when SHDN is asserted low, putting the

device in shutdown mode. The MAX3318E/MAX3319Es’

transmitters are turned off (high impedance) when

FORCEOFF is asserted low, or when the AutoShutdown

Plus circuitry senses that all receiver and transmitter

inputs are inactive for more than 30 seconds.

The transmitter outputs can be driven to ±12V when

power is off. The transmitter inputs do not have internal

RS-232 Receivers

The MAX3316E–MAX3319Es’ receivers convert ±3.7V

to ±13.2V RS-232 signal levels into CMOS-logic output

levels. The receivers are rated to receive signals up to

±25V. The MAX3316E/MAX3318E/MAX3319Es’

receivers feature inverting outputs that always remain

active (Table 1). The MAX3317E’s receivers have

inverting, three-state outputs. In shutdown, the

receivers can be active or inactive (Table 2).

The MAX3318E/MAX3319E feature an INVALID output

that is asserted low when no valid RS-232 voltage levels

have been detected on all receiver inputs. Because

INVALID indicates the receiver’s input condition, it

is independent of the states of FORCEON and

FORCEOFF.

MAX3317E Shutdown Mode

Supply current falls to less than 1µA in shutdown mode

(SHDN = low). When shut down, the device’s charge

pulled to ground, and the transmitter outputs are dis-

abled (high impedance). The time required to exit shut-

LapLink is a trademark of Traveling Software.

PIN

MAX3316E

MAX3317E MAX3318E MAX3319E

NAME

FUNCTION

Shutdown Control, Active Low

Ready to Transmit Output, Active High. READY is

enabled high when V- goes below -3.5V and the

device is ready to transmit.

Valid Signal Detector Output, Active Low. A logic

high indicates that a valid RS-232 level is present

on a receiver input.

Force-On Input, Active High. Drive high to override

AutoShutdown Plus, keeping transmitters and

receivers on (FORCEOFF must be high) (Table 1).

Force-Off Input, Active Low. Drive low to shut

down transmitters, receivers, and charge pump.

This overrides AutoShutdown Plus and FORCEON

(Table 1).

FORCEOFF

FORCEON

INVALID

READY

SHDN

—

1

10

12

16

20

14

11

1

—

20

—

—

—

—

—

—

—

—

—

SSOP

TSSOP