MAX3228E/AE and MAX3229E/AE feature a separate

and

INVALID outputs. The transmitter inputs (T_IN),

FORCEON and

This feature allows maximum flexibility in interfacing to

system’s logic supply voltage (+1.65V to +5.5V), and

bypass it with a 0.1µF capacitor to GND. If the logic

Software-Controlled Shutdown

If direct software control is desired, connect

FORCE-

OFF and FORCEON together to disable AutoShutdown.

The microcontroller then drives

FORCEOFF and

FORCEON like a

SHDN input, INVALID can be used to

alert the microcontroller to indicate serial data activity.

±15kV ESD Protection

As with all Maxim devices, ESD-protection structures are

incorporated on all pins to protect against electrostatic

discharges encountered during handling and assembly.

The driver outputs and receiver inputs of the

MAX3228E/AE and MAX3229E/AE have extra protection

against static electricity. Maxim’s engineers have devel-

oped state-of-the-art structures to protect these pins

against ESD of ±15kV without damage. The ESD struc-

tures withstand high ESD in all states: normal operation,

shutdown, and powered down. After an ESD event

Maxim’s E versions keep working without latchup,

whereas competing RS-232 products can latch and

must be powered down to remove latchup.

ESD protection can be tested in various ways; the trans-

mitter outputs and receiver inputs of this product family

are characterized for protection to the following limits:

1) ±15kV using the Human Body Model.

2) ±8kV using the Contact Discharge method specified

in IEC 1000-4-2.

3) ±15kV using the IEC 1000-4-2 Air-Gap method.

ESD Test Conditions

ESD performance depends on a variety of conditions.

Contact Maxim for a reliability report that documents test

setup, test methodology, and test results.

Human Body Model

Figure 5a shows the Human Body Model, and Figure 5b

shows the current waveform it generates when dis-

charged into a low impedance. This model consists of a

100pF capacitor charged to the ESD voltage of interest,

which is then discharged into the test device through a

1.5kΩ resistor.

Table 3. Output Control Truth Table

TRANSCEIVER STATUS

FORCEON

FORCEOFF

RECEIVER STATUS

INVALID

Shutdown (AutoShutdown)

Low

High

High-Z

L

Shutdown (Forced Off)

X

Low

High-Z

†

Normal Operation (Forced On)

High

High

Active

†

Normal Operation (AutoShutdown)

Low

High

Active

H

X = Don’t care.

† = I

NVALID output state is determined by R_IN input levels.

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

Ω

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 5a. Human Body ESD Test Models

90%

36.8%

TIME

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

Ir

10%

0

0

AMPERES

Figure 5b. Human Body Model Current Waveform

±15kV ESD-Protected +2.5V to +5.5V

RS-232 Transceivers in UCSP and WLP

_______________________________________________________________________________________

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