not the absolute voltages. Increasing the size of C1 and

C2 increases the time V+ and V- take to reach their final

µF close to

the MAX3212. Increase this to 4.7

µF if there are no other

(15cm) away from the MAX3212.

Component suppliers are listed in Table 1.

RS-232 Drivers

All three drivers are identical and deliver EIA/TIA-232E

tween 2.7V and 3.6V. When FORCEOFF is driven low or

when the AutoShutdown circuitry senses invalid voltage

levels at all receiver inputs, the drivers are disabled

and the outputs are forced into a high-impedance

state.

RS-232 Receivers

The MAX3212 receivers convert RS-232 signals to

CMOS-logic output levels. All receivers have one in-

verting three-state output. Receiver 5 also has a com-

plementary (noninverting) output. In shutdown, all five

inverting receivers can be either active or inactive

under logic control.

The complementary output (R5OUTB) is always active,

regardless of the state of EN or the part’s shutdown sta-

tus. R5OUTB can monitor RS-232 activity while the

other receivers are high impedance. This allows Ring

Indicator to be monitored without forward biasing other

devices connected to the receiver outputs. This is ideal

down. (See Figure 2.)

Enable Control

The EN input has two functions: It allows enabling/dis-

abling of the receivers, and it is used to reset the transi-

tion detector.

Driving EN low places five inverting receiver outputs

(R_OUT) into a high-impedance state. R5OUTB is

always active, regardless of the state of EN or the part’s

shutdown status (Table 2). EN has no effect on T_OUT.

EN also resets the transition detector. Drive EN high and

then low to reset the TRAN output low. TRAN goes high

when a transition occurs on any receiver input.

+2.7V to +3.6V-Powered, 1µA Supply Current,

3-Driver/5-Receiver, True RS-232 Transceiver

6

_______________________________________________________________________________________

Table 1. Suggested Component Suppliers

Table 2. AutoShutdown Logic

MANUFACTURER

PART NUMBER

PHONE

FAX

Motorola

MMBD6050LT1

USA (408) 749-0510

USA (408) 991-7420

Murata-Erie

LQH4N150K-TA

USA (404) 436-1300

Japan (075) 951-9111

USA (404) 684-1541

Japan (075) 955-6526

Sumida

CD43150

USA (708) 956-0666

Japan (03) 3607-5111

USA (708) 956-0702

Japan (03) 3607-5428

TDK

NLC453232T-150K

USA (708) 803-6100

Japan (03) 3278-5111

USA (708) 803-6296

Japan (03) 3278-5358

Allegro

TMPD6050LT

USA (508) 853-5000

USA (508) 853-5049

Philips

PMBD6050

USA (401) 762-3800

USA (401) 767-4493

RS-232 SIGNAL

PRESENT AT

RECEIVER INPUT

FORCEOFF INPUT

FORCEON

INPUT

INVALID OUTPUT

TRANSCEIVER STATUS

Yes

H

X

H

Normal Operation

No

H

H

L

Normal Operation (Forced On)

No

H

L

L

Shutdown (AutoShutdown)

Yes

L

X

H

Shutdown (Forced Off)

No

L

X

L

Shutdown (Forced Off)

Diodes

Inductors