Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsInterface ICsInterface IC - transceivers RS232 2/2 SSOP 20

_______________General Description

The MAX3218 RS-232 transceiver is intended for bat -

tery-powered EIA/TIA-232E and V.28/V.24 communica-

tions interfaces that need two drivers and two receivers

with minimum power consumption from a single low-

voltage supply. It provides a wide +1.8V to +4.25V

operating voltage range while maintaining true RS-232

and EIA/TIA-562 voltage levels. The MAX3218 runs

from two alkaline, NiCd, or NiMH cells without any form

of voltage regulator. A guaranteed 120kbps data rate

provides compatibility with popular software for com -

municating with personal computers.

Supply current is reduced to 1 µA with Maxim’s new

AutoShutdown™ feature. When the MAX3218 does not

sense a valid signal level on the receiver inputs, the on-

board power-supply and drivers shut down. This

occurs if the RS-232 cable is disconnected or if the

transmitters of the connected peripheral are turned off.

The system turns on again when a valid level is applied

to either RS-232 receiver input. As a result, the system

saves power without changes to the existing software.

Additionally, the MAX3218 can be forced into or out of

shutdown, under logic control.

While shut down, all receivers can remain active or can

be disabled under logic control, permitting a system

incorporating the CMOS MAX3218 to monitor external

devices while in low-power shutdown. Three-state dri -

vers are provided on both receiver outputs so that multi -

ple receivers, generally of different interface standards,

can be on the same bus. The MAX3218 is available in

20-pin DIP and SSOP packages.

________________________Applications

Battery-Powered Equipment

Subnotebook Computers

PDAs

Hand-Held Equipment

Peripherals

Cellular Phones

____________________________Features

BETTER THAN BIPOLAR!

♦ 1µA Supply Current Using AutoShutdown™

♦ Operates Directly from Two Alkaline,

NiCd or NiMH Cells

♦ +1.8V to +4.25V Single-Supply Voltage Range

♦ 120kbps Data Rate Guaranteed

♦ Low-Cost Surface-Mount Components

♦ Meets EIA/TIA-232E Specifications

♦ Three-State Receiver Outputs

♦ Flow-Through Pinout

♦ On-Board DC-DC Converters

♦ 20-Pin SSOP and DIP Packages

______________Ordering Information

†

Contact factory for dice specifications.

MAX3218*

1µA Supply Current, 1.8V to 4.25V-Powered

RS-232 Transceiver with AutoShutdown™

________________________________________________________________

Maxim Integrated Products

Call toll free 1-800-998-8800 for free samples or literature.

PART

MAX3218CPP

MAX3218CAP 0°C to +70°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

20 Plastic DIP

20 SSOP

19-0380; Rev 0; 3/95

MAX3218C/D

MAX3218EPP -40°C to +85°C

0°C to +70°C Dice

†

20 Plastic DIP

™ AutoShutdown is a trademark of Maxim Integrated Products.

MAX3218EAP -40°C to +85°C 20 SSOP

GND

V+

C1+

GND

FORCEON

FORCEOFF

INVALID

TOP VIEW

C1-

V-

T1OUT

T2OUT

T2IN

T1IN

GND

R1IN

R2IN

R2OUT

R1OUT

DIP/SSOP

MAX3218

__________________Pin Configuration

Summary of content (12 pages)

PAGE 1
9-0380; Rev 0; 3/95 1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ The MAX3218 RS-232 transceiver is intended for bat tery-powered EIA/TIA-232E and V.28/V.24 communications interfaces that need two drivers and two receivers with minimum power consumption from a single lowvoltage supply. It provides a wide +1.8V to +4.25V operating voltage range while maintaining true RS-232 and EIA/TIA-562 voltage levels.
PAGE 2
MAX3218 1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ ABSOLUTE MAXIMUM RATINGS Supply Voltages VCC ....................................................................-0.3V to +4.6V V+ .......................................................... (VCC - 0.3V) to +7.5V V- .......................................................................+0.3V to -7.4V VCC to V- ..........................................................................+12V LX ..............................
PAGE 3
1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ (Circuit of Figure 1, V CC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, T Typical values are at VCC = 3.0V, TA = +25°C.) PARAMETER CONDITIONS A = T MIN to T MAX, unless otherwise noted. MIN TYP MAX UNITS +25 V EIA/TIA-232E RECEIVER INPUTS Input Voltage Range Input Threshold Low Input Threshold High -25 VCC = 2.0V to 4.25V 0.4 VCC = 1.8V to 4.25V 0.3 V VCC = 1.8V to 4.25V 3.0 VCC = 1.8V to 3.
PAGE 4
__________________________________________Typical Operating Characteristics (Circuit of Figure 1, VCC = 1.8V, all transmitter outputs loaded with 3kΩ, TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. SUPPLY VOLTAGE TRANSMITTING SUPPLY CURRENT vs. LOAD CAPACITANCE SUPPLY CURRENT (mA) VCC = 2.
PAGE 5
1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ PIN NAME FUNCTION 1 LX 2 INVALID 3 FORCEON Drive high when FORCEOFF = high to override automatic circuitry, keeping transmitters on. 4 FORCEOFF Drive low to shut down transmitters and on-board power supply, overriding all automatic circuitry and FORCEON. 5, 17, 20 GND Ground 6 VCC Supply Voltage Input, 1.8V to 4.25V. Bypass to GND with at least 1µF.
PAGE 6
MAX3218 1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ Table 1.
PAGE 7
1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ POWER MANAGEMENT UNIT OR KEYBOARD CONTROLLER MAX3218 FORCEON FORCEOFF X H H X L L RECEIVER STATUS Receiver Enabled Receiver Disabled Shutdown CPU I/O CHIP WITH UART RS-232 When FORCEOFF is low, power supplies are disabled and the transmitters are placed in a high-impedance state. Receiver operation is not affected by taking FORCEOFF low. Power consumption is dramatically reduced in shutdown mode.
PAGE 8
MAX3218 1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ MAX3218 shuts down after sensing invalid RS-232 levels for greater than 30 µs, ensuring that the AutoShutdown mode is not enabled for slow-moving signals (>1V/µs). Another system with AutoShutdown may need a period of time to wake up. Figure 5 shows a circuit that forces the transmitters on for 100ms after start-up, allowing enough time for the other system to realize that the MAX3218 system is awake.
PAGE 9
Keep communications cables short to minimize capacitive loading. Lowering the capacitive loading on the transmitter outputs reduces the MAX3218’s power consumption. Using short, low-capacitance cable also helps transmission at the highest data rates. TRANSMITTERS ENABLED, INVALID HIGH EIA/TIA-232E and _____________EIA/TIA-562 Standards +2.8V INDETERMINATE +0.3V 0V AUTOSHUTDOWN, TRANSMITTERS DISABLED, 1µA SUPPLY CURRENT, INVALID LOW -0.3V INDETERMINATE -2.
PAGE 10
MAX3218 1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ 15µH 3V DC-DC CONVERTER MAX878 OR MAX756 OR MAX856 1N6050 1µF C2 C5 1µF 6 C4 0.1µF 3 4 2 VCC 1 LX 19 V+ V- 15 C3 1µF FORCEON C1+ FORCEOFF INVALID 7 T1IN 8 T2IN 9 R1OUT 18 C1 0.47µF MAX3218 C1- 16 T1OUT 14 T1 T2OUT 13 T2 R1IN 12 R1 5k 10 R2OUT R2IN 11 R2 5k GND 5, 17, 20 Figure 6.
PAGE 11
1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ PART SUPPLY VOLTAGE (V) No. OF TRANSMITTERS/ RECEIVERS No. OF RECEIVERS ACTIVE IN SHUTDOWN GUARANTEED DATA RATE (kbps) EIA/TIA232 OR 562 MAX212 3.0 to 3.6 3/5 5 120 232 Drives mice MAX3212 2.7 to 3.6 3/5 5 120 232 AutoShutdown, complementary receiver, drives mice, transient detection MAX218 1.8 to 4.25 2/2 2 120 232 Operates directly from a battery without a voltage regulator MAX3218 1.8 to 4.
PAGE 12
MAX3218 1µA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown™ ___________________Chip Topography INVALID LX GND V+ FORCEON C1+ FORCEOFF GND C1V- 0.101" (2.565mm) GND V CC T1OUT T1IN T2OUT T2IN R1IN R2OUT R2IN R1OUT 0.122" (3.099mm) TRANSISTOR COUNT: 571 SUBSTRATE CONNECTED TO GND ________________________________________________________Package Information DIM α E H C L A A1 B C D E e H L α INCHES MILLIMETERS MIN MAX MIN MAX 0.068 1.99 1.73 0.078 0.002 0.21 0.05 0.