Maxim MAX3218CAP, MAX3218EAP, MAX3218CPP, MAX3218C-D, MAX3218EPP Datasheet

19-0380; Rev 0; 3/95

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

RS-232 Transceiver with AutoShutdown™

_______________General Description

The MAX3218 RS-232 transceiver is intended for bat­tery-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. 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 com­municating with personal computers.

Supply current is reduced to 1µA with Maxim’s new
AutoShutdown™ feature. When the MAX3218 does not
sense a valid signal level on the receiver inputs, the on­board 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 dri­vers are provided on both receiver outputs so that multi­ple receivers, generally of different interface standards,
can be on the same bus. The MAX3218 is available in
20-pin DIP and SSOP packages.

____________________________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

PART

MAX3218CPP
MAX3218CAP 0°C to +70°C
MAX3218C/D
MAX3218EPP -40°C to +85°C
MAX3218EAP -40°C to +85°C 20 SSOP

†

Contact factory for dice specifications.

TEMP. RANGE PIN-PACKAGE

0°C to +70°C

0°C to +70°C Dice

20 Plastic DIP
20 SSOP

†

20 Plastic DIP

MAX3218*

________________________Applications

__________________Pin Configuration

Battery-Powered Equipment
Subnotebook Computers
PDAs
Hand-Held Equipment
Peripherals
Cellular Phones

* Patent Pending
™ AutoShutdown is a trademark of Maxim Integrated Products.

________________________________________________________________

TOP VIEW

INVALID

FORCEON

FORCEOFF

GND

V
T1IN
T2IN

R1OUT
R2OUT

LX

1
2
3
4

MAX3218

5
6

CC

7
8
9

10

DIP/SSOP

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

GND

20

V+

19

C1+

18

GND

17

C1-

16

V-

15

T1OUT

14

T2OUT

13

R1IN

12

R2IN

11

Maxim Integrated Products

1

1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™

ABSOLUTE MAXIMUM RATINGS

Supply Voltages

....................................................................-0.3V to +4.6V

V

CC

V+.......................................................... (V

V-.......................................................................+0.3V to -7.4V

to V-..........................................................................+12V

V

CC

LX ................................................................-0.3V to (1V + V+)

Input Voltages

T_IN, FORCEON, FORCEOFF

R_IN.................................................................................±25V

MAX3218

Output Voltages

T_OUT.............................................................................±15V)

R_OUT....................................................-0.3V to (V

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

............................ -0.3V to +7V

- 0.3V) to +7.5V

CC

CC

+ 0.3V)

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VCC= 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA= T
Typical values are at V

DC CHARACTERISTICS

Supply Current, Shutdown µA
Supply Current,

AutoShutdown™ Disabled

LOGIC INPUTS AND RECEIVER OUTPUTS

Input Logic Threshold Low
Input Logic Threshold High

AUTOSHUTDOWN (FORCEON = GND, FORCEOFF = VCC)

Receiver Input Thresholds,
Transmitters Enabled

Receiver Input Thresholds
Transmitters Disabled

INVALID Output Low Voltage 0.4
INVALID Output High Voltage V

= 3.0V, TA= +25°C.)

CC

VCC= 3.0V, TA= +25°C, all R_IN open,
FORCEON = GND, FORCEOFF = V

FORCEOFF = GND, TA= +25°C, VCC= 3.0V
FORCEON = FORCEOFF = VCC= 3.0V, no load mA2.0 3.0

T_IN, FORCEON, FORCEOFF
T_IN, FORCEON, FORCEOFF
T_IN, FORCEON = FORCEOFF = 0V or V
R_OUT, I
R_OUT, I
R_OUT, 0V ≤ R_OUT ≤ VCC,

FORCEON = FORCEOFF = 0V

Figure 4a

1µA supply current, Figure 4a
I

OUT

I

OUT

CONDITIONS

= 1.0mA

OUT

= -0.4mA

OUT

Positive threshold
Negative threshold -2.8

= 1.0mA, -0.3V < R_IN < 0.3V
= -0.4mA, |R_IN|> 2.8V

Short-Circuit Duration, R_OUT, T_OUT to GND ....... Continuous

Continuous Power Dissipation (T

Plastic DIP (derate 11.11mW/°C above +70°C) ..........889mW

SSOP (derate 8.00mW/°C above +70°C) ..................640mW

Operating Temperature Ranges

MAX3218C_ P................................................... 0°C to +70°C

MAX3218E_ P................................................. -40°C to +85°C

Storage Temperature Range ........................... -65°C to +150°C

Lead Temperature (soldering, 10sec) ........................... +300°C

CC

CC

CC

VCC- 0.25

MIN

A

to T

= +70°C)

, unless otherwise noted.

MAX

1.0 10

CC

2.8

UNITSMIN TYP MAXPARAMETER

V1.8 4.25Operating Voltage Range

µA1.0 10Supply Current, AutoShutdown™

V0.33 x V
V0.67 x V

µA0.001 ±1Input Leakage Current

V0.4Output Voltage Low
VVCC- 0.25 VCC- 0.08Output Voltage High

µA0.05 ±10Output Leakage Current

V

V-0.3 0.3
V

2 _______________________________________________________________________________________

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

RS-232 Transceiver with AutoShutdown™

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VCC= 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA= T
Typical values are at V

EIA/TIA-232E RECEIVER INPUTS

Input Threshold Low

Input Threshold High
Input Hysteresis V

Input Resistance

EIA/TIA-232E TRANSMITTER OUTPUTS

Output Short-Circuit Current mA

= 3.0V, TA= +25°C.)

CC

VCC= 2.0V to 4.25V
VCC= 1.8V to 4.25V
VCC= 1.8V to 4.25V
V

CC

-15V < R_IN < 15V kΩ357

All transmitter outputs loaded with 3kΩ to groundOutput Voltage Swing V±5 ±6
VCC= 0V, -2V < T_OUT < 2V

CONDITIONS

0.4

0.3

= 1.8V to 3.6V

to T

MIN

MAX

0.7

±24 ±100

, unless otherwise noted.

UNITSMIN TYP MAXPARAMETER

3.0

2.8

TIMING CHARACTERISTICS

(Circuit of Figure 1, VCC= 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA= T
Typical values are at V

= 3.0V, TA= +25°C.)

CC

MIN

to T

, unless otherwise noted.

MAX

MAX3218

V-25 +25Input Voltage Range
V

V

Ω300Output Resistance

Receiver Output Enable Time
Receiver Output Disable Time
Transmitter Output Enable Time
Transmitter Output Disable Time

Receiver Propagation Delay

Transmitter Propagation Delay

AUTOSHUTDOWN TIMING

Receiver Threshold to
Transmitters Enabled

Receiver Positive or Negative
Threshold to INVALID High

Receiver Positive or Negative
Threshold to INVALID Low

ER
DR
ET

DT
PHLR
PLHR
PHLT
PLHT

WU

INVH

INVL

CONDITIONS

2500pF || 3kΩ load each transmitter, one trans­mitter switching, 150pF load each receiver

150pF load
150pF load
2500pF || 3kΩ load
2500pF || 3kΩ load
TA= +25°C, VCC= 3.0V, RL= 3kΩ to 7kΩ,

CL= 50pF to 2500pF, measured from
+3V to -3V or -3V to +3V

Figure 4b µs250t

Figure 4b µs1t

Figure 4b µs30t

UNITSMIN TYP MAXSYMBOLPARAMETER

kbps120 235Data Rate

ns90 300t
ns200 500t
µs250 450t

ns500t
290 1000t
260 1000t

1.9 2.7t

1.8 2.7t

ns

µs

V/µs3.0 30Transition Region Slew Rate

_______________________________________________________________________________________ 3

1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™

__________________________________________Typical Operating Characteristics

(Circuit of Figure 1, VCC= 1.8V, all transmitter outputs loaded with 3kΩ, TA = +25°C, unless otherwise noted.)

140

120

MAX3218

100

80

60

40

SUPPLY CURRENT (mA)

20

0

SUPPLY CURRENT vs.

SUPPLY VOLTAGE

1 TRANSMITTER FULL DATA RATE
1 TRANSMITTER 1/8 DATA RATE
RL = 3kΩ + 2500pF

240kbps

120kbps

20kbps

0kbps

2.4 3.0

1.8
SUPPLY VOLTAGE (V)

3.6

4.2

2V/div

MAX3218-01

TIME TO EXIT SHUTDOWN

(ONE TRANSMITTER HIGH,

ONE TRANSMITTER LOW)

TRANSMITTING SUPPLY CURRENT

vs. LOAD CAPACITANCE

100

VCC = 2.4V

90
80

235kbps
70
60

120kbps
50

SUPPLY CURRENT (mA)

40

20kbps

30
20

1000

0

LOAD CAPACITANCE (pF)

FORCEON, FORCEOFF

V

OH

T_OUT

TRANSMITTER 1 OPERATING 
AT SPECIFIED BIT RATE, 
TRANSMITTER 2 OPERATING 
AT 1/16 THAT RATE.


3000

2000

4000

MAX3218-02

5000

V

1.8V

TRANSMITTER OUTPUT VOLTAGE vs. 

LOAD CAPACITANCE AT 120kbps

8
6
4
2

0

-2

-4

TRANSMITTER OUTPUT VOLTAGE (V)

-6

-8
1000

0

LOAD CAPACITANCE (pF)

2000

3000

V

V

OUT+

OUT-

4000

R

MAX3218-04

5000

CC =

= 3kΩ || 2500pF

L

100µs/div

V

OL

SLEW RATE vs.

TRANSMITTER CAPACITANCE

12

10

8

6

4

SLEW RATE (V/µs)

DATA RATE 120kbps,
TRANSMITTERS LOADED WITH 

2

3kΩ PLUS INDICATED CAPACITANCE


0

1000

0

+SLEW

-SLEW

2000

3000

LOAD CAPACITANCE (pF)

4 _______________________________________________________________________________________

4000

MAX3218-05

5000

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

RS-232 Transceiver with AutoShutdown™

______________________________________________________________Pin Description

PIN

1

6

Inductor/Diode Connection PointLX

INVALID2

FORCEOFF4

CC

Output of Invalid Signal Detector. Low if invalid RS-232 levels are present on all receiver inputs,
otherwise high.

Drive high when FORCEOFF = high to override automatic circuitry, keeping transmitters on.FORCEON3
Drive low to shut down transmitters and on-board power supply, overriding all automatic

circuitry and FORCEON.
GroundGND5, 17, 20
Supply Voltage Input, 1.8V to 4.25V. Bypass to GND with at least 1µF.V
Transmitter InputsT1IN, T2IN7, 8
Receiver OutputsR1OUT, R2OUT9, 10
Receiver InputsR2IN, R1IN11, 12
Transmitter Outputs, swing between V+ and V-T2OUT, T1OUT13, 14
Negative Supply generated on-boardV-15
Terminal for Charge-Pump CapacitorC1-, C1+16, 18
Positive Supply generated on-boardV+19

FUNCTIONNAME

MAX3218

_______________Detailed Description

The MAX3218 line driver/receiver is intended for bat­tery-powered EIA/TIA-232 and V.28/V.24 communica­tions interfaces that require two drivers and two
receivers. The operating voltage extends from 1.8V to

4.25V, yet the device maintains true RS-232 and
EIA/TIA-562 transmitter output voltage levels. This wide
supply voltage range permits direct operation from a
variety of batteries without the need for a voltage regu­lator. For example, the MAX3218 can be run directly
from a single lithium cell or a pair of alkaline cells. It
can also be run directly from two NiCd or NiMH cells
from full-charge voltage down to the normal 0.9V/cell
end-of-life point. The 4.25V maximum supply voltage
allows the two rechargeable cells to be trickle- or fast­charged while driving the MAX3218.

The circuit comprises three sections: power supply,
transmitters, and receivers. The power-supply section
converts the supplied input voltage to 6.5V, providing the
voltages necessary for the drivers to meet true RS-232
levels. External components are small and inexpensive.

The transmitters and receivers are guaranteed to oper­ate at 120kbps data rates, providing compatibility with
LapLink™ and other high-speed communications soft­ware.

The MAX3218 is equipped with Maxim’s new propri­etary AutoShutdown™ circuitry. This achieves a 1µA
supply current by shutting down the device when the
RS-232 cable is disconnected or when the connected
peripheral transmitters are turned off. While shut down,
both receivers can remain active or can be disabled
under logic control. With this feature, the MAX3218 can
be in low-power shutdown mode and still monitor activi­ty on external devices. Three-state drivers are provid­ed on both receiver outputs.

Three-state drivers on both receiver outputs are provid­ed so that multiple receivers, generally of different inter­face standards, can be wire-ORed at the UART.

Switch-Mode Power Supply

The switch-mode power supply uses a single inductor
with one diode and three small capacitors to generate
±6.5V from an input voltage in the 1.8V to 4.25V range.

Inductor Selection

Use a 15µH inductor with a saturation current rating of at
least 350mA and less than 1Ω resistance. Table 1 lists
suppliers of inductors that meet the 15µH/350mA/1Ω
specifications.

™ LapLink is a trademark of Traveling Software, Inc.

AutoShutdown is a trademark of Maxim Integrated Products.

_______________________________________________________________________________________ 5

1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™

Table 1. Suggested Component Suppliers

MANUFACTURER PHONEPART NUMBER FAX

Inductors

USA [phone]LQH4N150K-TAMurata-Erie USA [phone]

MAX3218

Diodes—Surface-Mount

Diodes—Through-Hole

Motorola

CD43150Sumida

NLC453232T-150KTDK

1N5817 (Schottky)

USA [phone]
Japan [phone]

USA [phone]
Japan [phone]

USA [phone]TMPD6050LTAllegro USA [phone]
USA [phone]CMPSH-3 (Schottky)Central Semiconductor USA [phone]
USA [phone]MMBD6050LT1 (silicon)Motorola USA [phone]
USA [phone]PMBD6050 (silicon)Philips USA [phone]

USA [phone]1N6050 (silicon),

USA [phone]
Japan [phone]

USA [phone]
Japan [phone]

USA [phone]

Diode Selection

Key diode specifications are fast recovery time (<10ns),
average current rating (>100mA), and peak current rat­ing (>350mA). Inexpensive fast silicon diodes, such as
the 1N6050, are generally recommended. More expen­sive Schottky diodes improve efficiency and give slightly
better performance at very low VCCvoltages. Table 1
lists suppliers of both surface-mount and through-hole
diodes. 1N914s are usually satisfactory, but specifica­tions and performance vary widely with different manu­facturers.

Capacitor Selection

Use capacitors with values at least as indicated in
Figure 1. Capacitor C2 determines the ripple on V+, but
not the absolute voltage. Capacitors C1 and C3 deter­mine both the ripple and the absolute voltage of V-.
Bypass VCCto GND with at least 1µF (C4) placed close
to pins 5 and 6. If the VCCline is not bypassed else­where (e.g., at the power supply), increase C4 to 4.7µF.

You may use ceramic or polarized capacitors in all
locations. If you use polarized capacitors, tantalum
types are preferred because of the high operating fre­quency of the power supplies (about 250kHz). If alu­minum electrolytics are used, higher capacitance
values may be required.

1.8V to

4.25V
1µF

15µH 1N6050

C4

61
V

CC

3



FORCEON

4



FORCEOFF

2

INVALID

T1IN 14

7

8

T2IN

R1OUT

9

R2OUT

10

LX

MAX3218

T1

T2

R1

5k

R2

5k

GND

5, 17, 20

19

V+

V-

C1+

C1-

T1OUT

T2OUT

R1IN

R2IN

C2
1µF

15

C3
1µF

18

C1

0.47µF

16

13

12

11

Figure 1. Typical Operating Circuit

6 _______________________________________________________________________________________

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

RS-232 Transceiver with AutoShutdown™

FORCEOFF

POWER

MANAGEMENT

UNIT OR

KEYBOARD

CONTROLLER



CPU

Figure 2. Interface Under Control of PMU

FORCEON

INVALID

I/O

CHIP

WITH

UART

MAX3218

RS-232

RS-232 Drivers

The two drivers are identical, and deliver EIA/TIA-232E
and EIA/TIA-562 output voltage levels when VCCis
between 1.8V and 4.25V. One transmitter can drive up
to 3kΩ in parallel with 2500pF at up to 120kbps.
Connect unused drivers to either GND or VCC. When
FORCEOFF is driven low, or when AutoShutdown circuit­ry senses invalid voltage levels at all receiver inputs, the
drivers are disabled and their outputs are forced into a
high-impedance state. Driver inputs do not have internal
pull-up resistors.

RS-232 Receivers

The two receivers are identical, and accept both
EIA/TIA-232E and EIA/TIA-562 input signals. The
CMOS receiver outputs are inverting and swing rail-to­rail. Receivers are disabled only when FORCEON and
FORCEOFF inputs are low. (See Table 2.)

Table 2. Receiver Status

FORCEON FORCEOFF RECEIVER STATUS

HX
XH
LL

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. Supply current is minimized
when the receiver inputs are static in any one of three
states: floating (ground), GND, or VCC.

A 1µA supply current is achieved with Maxim’s new
AutoShutdown feature, which operates when FORCEON
is low and FORCEOFF is high. When the MAX3218
senses no valid signal level on either receiver input for
typically 30µs, the on-board power supply and drivers
shut down, reducing supply current to 1µA. Internal 5kΩ
resistors pull undriven receiver inputs to ground. This
occurs if the RS-232 cable is disconnected or if the con­nected peripheral transmitters 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 BIOS or operating
system. When using the AutoShutdown feature, INVALID
is high when the device is on and low when the device is
shut down. The INVALID output indicates the condition
of the receiver inputs.

Table 3 summarizes the MAX3218 operating modes.
FORCEON and FORCEOFF override the automatic cir­cuitry and force the transceiver into its normal operating
state or into its low-power standby state. When neither
control is asserted, the IC selects between these states
automatically based on receiver input levels. Figure 4
depicts valid and invalid RS-232 receiver levels. The

Receiver Enabled
Receiver Disabled

Shutdown

AutoShutdown™

MAX3218

Table 3. AutoShutdown Logic

RS-232 SIGNAL

PRESENT AT

RECEIVER INPUT

_______________________________________________________________________________________ 7

INVALID OUTPUTFORCEOFF INPUT TRANSCEIVER STATUSFORCEON INPUT

X
H

L
X
X

HHYes Normal Operation

LHNo Normal Operation (Forced On)
LHNo Shutdown (AutoShutdown)

HLYes Shutdown (Forced Off)

LLNo Shutdown (Forced Off)

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 30µs, 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. If the other system outputs
valid RS-232 signals within that time, the RS-232 ports on

MAX3218

both systems remain enabled.

__________Applications Information

Operation from Regulated/Unregulated

Dual System Power Supplies

The MAX3218 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 simulta­neously from both. Figure 1 shows the single-supply
configuration. Figure 6 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
MAX3218’s logic levels remain appropriate for interface
with 3V logic, yet most of the power for the MAX3218 is

drawn directly from the battery, without suffering the
efficiency losses of the DC-DC converter. This pro­longs battery life.

Bypass the input supplies with 0.1µF at V

(C4) and at

CC

least 1µF at the inductor (C5). Increase C5 to 4.7µF if
the power supply has no other bypass capacitor con­nected to it.

Low-Power Operation

The following suggestions will help you get maximum
life out of your batteries.

Transmit at the highest practical data rate. Although
this raises the supply current while transmission is in
progress, the transmission will be over sooner. If the
MAX3218 is shut down (using FORCEOFF) as soon as
each transmission ends, this practice will save energy.

Operate your whole system from the raw battery volt­age rather than suffer the losses of a regulator or DC­DC converter. If this is not possible, but your system is
powered from two cells and employs a 3V DC-DC con­verter to generate the main logic supply, use the circuit
of Figure 6. This circuit draws most of the MAX3218’s
power straight from the battery, but still provides logic­level compatibility with the 3V logic.

+0.3V to +2.8V

-0.3V to -2.8V

+

-

+

-

RxR_IN

R_OUT

FORCEOFF

FORCEON

•

FORCEON

FORCEOFF

•

•

•

•

30µs

DELAY

INVALID

•

FORCEOFF

INVALID IS AN INTERNALLY GENERATED SIGNAL
THAT IS USED BY THE AUTOSHUTDOWN LOGIC
AND APPEARS AS AN OUTPUT OF THE DEVICE.

POWER DOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.

Figure 3. AutoShutdown Logic

8 _______________________________________________________________________________________

FORCEON
0
0
0
0
1
1
1
1

INVALID
0
0
1
1
0
0
1
1

0
1
0
1
0
1
0
1

POWER DOWN

POWER DOWN

0
0
0
0
0
1
1
1

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

RS-232 Transceiver with AutoShutdown™

TRANSMITTERS ENABLED, INVALID HIGH

+2.8V

INDETERMINATE

+0.3V

-0.3V

-2.8V

AUTOSHUTDOWN RECEIVER INPUT THRESHOLD (V)

(a)

RECEIVER

INPUT

VOLTAGE

(V)

AUTOSHUTDOWN, TRANSMITTERS DISABLED,

0V

1µA SUPPLY CURRENT, INVALID LOW

INDETERMINATE

TRANSMITTERS ENABLED, INVALID HIGH

INVALID
REGION

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.

EIA/TIA-232E and

_____________EIA/TIA-562 Standards

RS-232 circuits consume much of their power because
the EIA/TIA-232E standard demands that the transmit­ters deliver at least 5V to receivers with impedances
that can be as low as 3kΩ. For applications where
power consumption is critical, the EIA/TIA-562 standard
provides an alternative.

EIA/TIA-562 transmitter output voltage levels need only
reach ±3.7V, and because they have to drive the same
3kΩ receiver loads, the total power consumption is con­siderably reduced. Since the EIA/TIA-232E and
EIA/TIA-562 receiver input voltage thresholds are the
same, interoperability between EIA/TIA-232E and
EIA/TIA-562 devices is guaranteed. Maxim’s MAX560
and MAX561 are EIA/TIA-562 transceivers that operate
on a single supply from 3.0V to 3.6V, and the MAX562
transceiver operates from 2.7V to 5.25V while produc­ing EIA/TIA-562 levels.

MAX3218

V

CC

INVALID
OUTPUT

(V)

(b)

0

V+

V

CC

0V

V-

t

INVL

Figure 4. AutoShutdown Trip Levels

_______________________________________________________________________________________ 9

POWER

MANAGEMENT

UNIT

t

INVH

t

WU

MASTER SHDN LINE

FORCEOFF

0.1µF 1M

FORCEON

MAX3218

Figure 5. AutoShutdown with Initial Turn-On to Wake Up a
System

1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™

MAX3218

3V

DC-DC

CONVERTER



MAX878

OR

MAX756

OR

MAX856

15µH

C5
1µF


6

V



C4

0.1µF


CC

3



FORCEON

4



FORCEOFF

2

INVALID

T1IN 14

7

8

T2IN

9

R1OUT

R2OUT

10

1N6050

1

LX

MAX3218

T1

T2

GND

R1

R2

5, 17, 20

1µF

C2

19

V+

T1OUT

T2OUT

5k

5k

C1+

C1-

R1IN

R2IN

15

V-

18

16

13

12

11

C3

1µF

C1

0.47µF

Figure 6. Operating from Unregulated and Regulated Supplies

10 ______________________________________________________________________________________

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

RS-232 Transceiver with AutoShutdown™

_____+3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim

GUAR-

ANTEED

DATA

RATE

(kbps)

12053/52.7 to 3.6MAX3212

12022/21.8 to 4.25MAX218

12022/21.8 to 4.25MAX3218

EIA/TIA-

232

OR 562

232

232

232

232

562
562120

FEATURES

Drives mice12053/53.0 to 3.6MAX212
AutoShutdown, complementary

receiver, drives mice, transient
detection

Operates directly from a battery
without a voltage regulator

Same as MAX218 but with
AutoShutdown

Pin-compatible with MAX214
Wide supply range56223053/52.7 to 5.25MAX562

0.1µF capacitors56212022/23.0 to 3.6MAX563

0.1µF capacitors23212022/23.0 to 5.5MAX3222
AutoShutdown, 0.1µF capacitors23212022/23.0 to 5.5MAX3223

PART

MAX560

SUPPLY

VOLTAGE

(V)

3.0 to 3.6 Pin-compatible with MAX21312024/5

No. OF

TRANSMITTERS/

RECEIVERS

No. OF

RECEIVERS

ACTIVE IN

SHUTDOWN

4/53.0 to 3.6MAX561

0

MAX3218

12022/23.0 to 5.5MAX3232

23212053/53.0 to 5.5MAX3241

23212013/53.0 to 5.5MAX3243

Pin-compatible with MAX232232

0.1µF capacitors, 2 complemen­tary receivers, drives mice

0.1µF capacitors, AutoShutdown,
complementary receiver,
drives mice

______________________________________________________________________________________ 11

1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™

___________________Chip Topography

INVALID

FORCEON

FORCEOFF

MAX3218

GND

V

CC

T1IN

T2IN

LX

R1OUT

(3.099mm)

GND

R2OUT

0.122"

R2IN

R1IN

V+

C1+
GND

C1­V-

0.101"

(2.565mm)

T1OUT

T2OUT

TRANSISTOR COUNT: 571
SUBSTRATE CONNECTED TO GND

________________________________________________________Package Information

DIM

A

A1

B
C

α

HE

C

L

D
E
e
H
L

α

INCHES



MIN

0.068

0.002

0.010

0.004

0.205

0.301

0.025

MAX

0.078

0.008

0.015

0.008

SEE VARIATIONS



0.209



0.311

0.037

0˚





8˚

MILLIMETERS

MIN

1.73

0.05

0.25

0.09


5.20

0.65 BSC0.0256 BSC



7.65

0.63

0˚

MAX

1.99

0.21

0.38

0.20


5.38


7.90

0.95

8˚

14
16
20
24
28

INCHES

MIN



0.239

0.239

0.278

0.317

0.397

DIM

PINS

e

SSOP

A

SHRINK

SMALL OUTLINE

B

A1

PACKAGE



D
D
D
D
D

MAX

0.249

0.249

0.289

0.328

0.407

MILLIMETERS

MAX

MIN

6.33

6.07

6.33

6.07

7.33

7.07

8.33

8.07

10.33

10.07

21-0056A

D

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

12

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© 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.