MAX3228E(2001) Просмотр технического описания (PDF) - Maxim Integrated

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MAX3228E
(Rev.:2001)

±15kV ESD-Protected +2.5V to +5.5V RS-232 Transceivers in UCSP

Maxim Integrated 

±15kV ESD-Protected +2.5V to +5.5V

RS-232 Transceivers in UCSP

Table 3. Output Control Truth Table

TRANSCEIVER STATUS

Shutdown (AutoShutdown)

Shutdown (Forced Off)

Normal Operation (Forced On)

Normal Operation (AutoShutdown)

FORCEON

Low

X

High

Low

X = Don’t care.

† = INVALID output state is determined by R_IN input levels.

FORCEOFF

High

Low

High

High

RECEIVER STATUS

High-Z

High-Z

Active

Active

INVALID

L

†

†

H

MAX3228E/MAX3229E feature a separate logic supply

input (VL) that sets VOH for the receiver and INVALID

outputs. The transmitter inputs (T_IN), FORCEON and

FORCEOFF, are also referred to VL. This feature allows

maximum flexibility in interfacing to different systems

and logic levels. Connect VL to the system’s logic sup-

ply voltage (+1.65V to +5.5V), and bypass it with a

0.1µF capacitor to GND. If the logic supply is the same

as VCC, connect VL to VCC. Always enable VCC before

enabling the VL supply. VCC must be greater than or

equal to the VL supply.

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 electro-

static discharges encountered during handling and

assembly. The driver outputs and receiver inputs of the

MAX3228E/MAX3229E have extra protection against

static electricity. Maxim’s engineers have developed

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

ESD of ±15kV without damage. The ESD structures with-

stand high ESD in all states: normal operation, shut-

down, and powered down. After an ESD event Maxim’s

E versions keep working without latchup, whereas com-

peting 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.

RC 1MΩ

CHARGE-CURRENT

LIMIT RESISTOR

HIGH-

VOLTAGE

DC

SOURCE

Cs

100pF

RD 1500Ω

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

DEVICE

UNDER

TEST

Figure 5a. Human Body ESD Test Models

IP 100%

90%

Ir

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

AMPERES

36.8%

10%

0

0 tRL

TIME

tDL

CURRENT WAVEFORM

Figure 5b. Human Body Model Current Waveform

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.

_______________________________________________________________________________________ 9

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