MAX218CWP 查看數據表（PDF） - Maxim Integrated

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MAX218CWP

1.8V to 4.25V-Powered, True RS-232 Dual Transceiver

Maxim Integrated 

1.8V to 4.25V-Powered,

True RS-232 Dual Transceiver

Table 1. Suggested Component Suppliers

MANUFACTURER

Inductors—Surface Mount

PART NUMBER

Murata-Erie

LQH4N150K-TA

Sumida

CD43150

TDK

Diodes—Surface Mount

Central Semiconductor

Motorola

Philips

Diodes—Through-Hole

Motorola

NLC453232T-150K

CMPSH-3, Schottky

MMBD6050LT1, Silicon

PMBD6050, Silicon

1N6050, Silicon

1N5817, Schottky

PHONE

USA (404) 436-1300

Japan (075) 951-9111

USA (708) 956-0666

Japan (03) 3607-5111

USA (708) 803-6100

Japan (03) 3278-5111

USA (516) 435-1110

USA (408) 749-0510

USA (401) 762-3800

USA (408) 749-0510

FAX

USA (404) 436-3030

Japan (075) 955-6526

USA (708) 956-0702

Japan (03) 3607-5428

USA (708) 803-6296

Japan (03) 3278-5358

USA (516) 435-1824

USA (408) 991-7420

USA (401) 767-4493

USA (408) 991-7420

RS-232 Drivers

The two drivers are identical, and deliver EIA/TIA-232E

and EIA/TIA-562 output voltage levels when VDD is

between 1.8V and 4.25V. The transmitters drive up to

3kΩ in parallel with 1000pF at up to 120kbps. Connect

dufonrriuvceseerdsdibndtyoritvaaekhriniignghpS-—uimHt—sDp—teNo–dealointwhce.erTsGhtaeNteDtrwaonhrseVmnCiS—tCtHe.—rD—DoN–uistiapsbulolteswat.hree

RS-232 Receivers

The two receivers are identical, and accept both

EIA/TIA-232E and EIA/TIA-562 input signals. The

CMOS receiver outputs swing rail-to-rail. When EN is

hS—iHg—Dh—,N–t.heWrehceenivEeNrs

are active

is low, the

regardless of the

receiver outputs

state of

are put

into a high-impedance state. This allows two RS-232

ports (or two ports of different types) to be wired-ORed

at the UART.

S—H—D—N–

and

EN

determine

the

Operating Modes

MAX218’s mode of opera-

tion, as shown in Table 2.

Table 2. Operating Modes

–S—H—D—N–

EN

RECEIVER

OUTPUT

DRIVER

OUTPUT

DC-DC

CONVERTER

SUPPLY

CURRENT

L L High-Z High-Z

OFF

Minimum

L H Enabled High-Z

OFF

Minimum

H L High-Z Enabled

ON

Normal

H H Enabled Enabled

ON

Normal

When

S—H—D—N–

is

low,

the

power

supplies

are

Shutdown

disabled and

the transmitters are put

Receiver operation is not

inaftfoecatehdigbhy-imtapkiendgaS—nHc—eD—N–stlaotwe..

Power consumption is dramatically reduced in shutdown

mode. Supply current is minimized when the receiver

inputs are static in any of three states: floating (ground),

GND, or VCC.

__________Applications Information

Operation from Regulated/Unregulated

Dual System Power Supplies

The MAX218 is intended for use with three different

power-supply sources: it can be powered directly from

a battery, from a 3.0V or 3.3V power supply, or simulta-

neously from both. Figure 1 shows the single-supply

configuration. Figure 2 shows the circuit for operation

from both a 3V supply and a raw battery supply—an

ideal configuration where a regulated 3V supply is

being derived from two cells. In this application, the

MAX218’s logic levels remain appropriate for interface

with 3V logic, yet most of the power for the MAX218 is

drawn directly from the battery, without suffering the

efficiency losses of the DC-DC converter. This pro-

longs battery life.

Bypass the input supplies with 0.1µF at VCC (C4) and at

least 1µF at the inductor (C5). Increase C5 to 4.7µF if

the power supply has no other bypass capacitor con-

nected to it.

6 _______________________________________________________________________________________

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