_______________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
1
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
20
19
18
17
16
15
14
13
1
2
3
4
5
6
7
8
GND
V+
C1+
GND
FORCEON
FORCEOFF
INVALID
LX
TOP VIEW
C1-
V-
T1OUT
T2OUT
T2IN
T1IN
VCC
GND
12
11
9
10
R1IN
R2IN
R2OUT
R1OUT
DIP/SSOP
MAX3218
__________________Pin Configuration
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V CC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, T A= TMIN to TMAX, unless otherwise noted.
Typical values are at VCC = 3.0V, TA= +25°C.)
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.
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 ................................................................-0.3V to (1V + V+)
Input Voltages
T_IN, FORCEON, FORCEOFF ............................ -0.3V to +7V
R_IN .................................................................................±25V
Output Voltages
T_OUT.............................................................................±15V)
R_OUT....................................................-0.3V to (VCC + 0.3V)
Short-Circuit Duration, R_OUT, T_OUT to GND ....... Continuous
Continuous Power Dissipation (TA= +70°C)
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
VCC = 3.0V, TA= +25°C, all R_IN open,
FORCEON = GND, FORCEOFF = VCC
IOUT = -0.4mA,
|
R_IN
|
> 2.8V
IOUT = 1.0mA, -0.3V < R_IN < 0.3V
1µA supply current, Figure 4a
Figure 4a
R_OUT, IOUT = 1.0mA
T_IN, FORCEON = FORCEOFF = 0V or VCC
T_IN, FORCEON, FORCEOFF
FORCEOFF = GND, TA= +25°C, VCC = 3.0V
R_OUT, 0V ≤R_OUT ≤VCC,
FORCEON = FORCEOFF = 0V
T_IN, FORCEON, FORCEOFF
R_OUT, IOUT = -0.4mA
CONDITIONS
V
VCC - 0.25
INVALID Output Low Voltage 0.4
V-0.3 0.3
Receiver Input Thresholds
Transmitters Disabled
V
2.8
Receiver Input Thresholds,
Transmitters Enabled
µA0.05 ±10Output Leakage Current
VVCC - 0.25 VCC - 0.08Output Voltage High
µA1.0 10Supply Current, AutoShutdown™
V1.8 4.25Operating Voltage Range
V0.4Output Voltage Low
µA0.001 ±1Input Leakage Current
V0.67 x VCC
Input Logic Threshold High
1.0 10
V0.33 x VCC
Input Logic Threshold Low
UNITSMIN TYP MAXPARAMETER
FORCEON = FORCEOFF = VCC = 3.0V, no load mA2.0 3.0
Supply Current,
AutoShutdown™ Disabled
Supply Current, Shutdown µA
INVALID Output High Voltage V
DC CHARACTERISTICS
AUTOSHUTDOWN (FORCEON = GND, FORCEOFF = VCC)
LOGIC INPUTS AND RECEIVER OUTPUTS
Positive threshold
Negative threshold -2.8
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V CC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, T A= TMIN to TMAX, unless otherwise noted.
Typical values are at VCC = 3.0V, TA= +25°C.)
ns500tDT
Transmitter Output Disable Time
2500pF || 3kΩload each transmitter, one trans-
mitter switching, 150pF load each receiver
TA= +25°C, VCC = 3.0V, RL= 3kΩto 7kΩ,
CL= 50pF to 2500pF, measured from
+3V to -3V or -3V to +3V
2500pF || 3kΩload
150pF load
150pF load
2500pF || 3kΩload
CONDITIONS
ns200 500tDR
Receiver Output Disable Time
ns90 300tER
kbps120 235Data Rate
Receiver Output Enable Time
V/µs3.0 30Transition Region Slew Rate
1.8 2.7tPLHT
Transmitter Propagation Delay
µs250 450tET
Transmitter Output Enable Time
ns
290 1000tPHLR
260 1000tPLHR
Receiver Propagation Delay
µs
1.9 2.7tPHLT
UNITSMIN TYP MAXSYMBOLPARAMETER
TIMING CHARACTERISTICS
(Circuit of Figure 1, V CC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, T A= TMIN to TMAX, unless otherwise noted.
Typical values are at VCC = 3.0V, TA= +25°C.)
VCC = 2.0V to 4.25V
CONDITIONS
0.4
UNITSMIN TYP MAXPARAMETER
VCC = 1.8V to 4.25V
VCC = 1.8V to 4.25V
V
0.3
Input Threshold Low
3.0
-15V < R_IN < 15V kΩ357
V
CC = 1.8V to 3.6V
Input Resistance
Input Hysteresis V
V
2.8
Input Threshold High
0.7
VCC = 0V, -2V < T_OUT < 2V
Output Short-Circuit Current mA
Ω300Output Resistance
±24 ±100
All transmitter outputs loaded with 3kΩto groundOutput Voltage Swing V±5 ±6
V-25 +25Input Voltage Range
EIA/TIA-232E RECEIVER INPUTS
EIA/TIA-232E TRANSMITTER OUTPUTS
Figure 4b µs250tWU
Receiver Threshold to
Transmitters Enabled
Figure 4b µs1tINVH
Receiver Positive or Negative
Threshold to INVALID High
Figure 4b µs30tINVL
Receiver Positive or Negative
Threshold to INVALID Low
AUTOSHUTDOWN TIMING
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
4 _______________________________________________________________________________________
8
-8 0
TRANSMITTER OUTPUT VOLTAGE vs.
LOAD CAPACITANCE AT 120kbps
MAX3218-04
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
3000
0
-2
-6
-4
1000 2000 5000
6
4
2
4000
VOUT+
VOUT-
12
0
SLEW RATE vs.
TRANSMITTER CAPACITANCE
MAX3218-05
LOAD CAPACITANCE (pF)
SLEW RATE (V/µs)
3000
4
2
01000 2000 5000
10
8
6
4000
+SLEW
-SLEW
DATA RATE 120kbps,
TRANSMITTERS LOADED WITH
3kΩ PLUS INDICATED CAPACITANCE
__________________________________________Typical Operating Characteristics
(Circuit of Figure 1, VCC = 1.8V, all transmitter outputs loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
120
140
01.8
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX3218-01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
3.6
60
40
20
2.4 3.0
80
100
4.2
1 TRANSMITTER FULL DATA RATE
1 TRANSMITTER 1/8 DATA RATE
RL = 3kΩ + 2500pF
240kbps
120kbps
20kbps
0kbps
100
20 0
TRANSMITTING SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3218-02
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
3000
60
50
30
40
1000 2000 5000
90
80
70
4000
20kbps
120kbps
VCC = 2.4V
TRANSMITTER 1 OPERATING
AT SPECIFIED BIT RATE,
TRANSMITTER 2 OPERATING
AT 1/16 THAT RATE.
235kbps
VOH
FORCEON, FORCEOFF
T_OUT
2V/div
VOL
TIME TO EXIT SHUTDOWN
(ONE TRANSMITTER HIGH,
ONE TRANSMITTER LOW)
100µs/div
VCC = 1.8V
RL = 3kΩ || 2500pF
_______________Detailed Description
The MAX3218 line driver/receiver is intended for bat-
tery-powered EIA/TIA-232 and V.28/V.24 communica -
tions 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 regu-
lator. 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 fast-
charged 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 oper-
ate at 120kbps data rates, providing compatibility with
LapLink™ and other high-speed communications soft-
ware.
The MAX3218 is equipped with Maxim’s new propri -
etary 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 activi-
ty on external devices. Three-state drivers are provid-
ed on both receiver outputs.
Three-state drivers on both receiver outputs are provid-
ed so that multiple receivers, generally of different inter-
face 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 1 Ωresistance. Table 1 lists
suppliers of inductors that meet the 15 µH/350mA/1Ω
specifications.
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
_______________________________________________________________________________________ 5
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
GroundGND5, 17, 20
Supply Voltage Input, 1.8V to 4.25V. Bypass to GND with at least 1µF.VCC
6
Transmitter InputsT1IN, T2IN7, 8
Receiver OutputsR1OUT, R2OUT9, 10
Drive low to shut down transmitters and on-board power supply, overriding all automatic
circuitry and FORCEON.
FORCEOFF4
Drive high when FORCEOFF = high to override automatic circuitry, keeping transmitters on.FORCEON3
PIN
Output of Invalid Signal Detector. Low if invalid RS-232 levels are present on all receiver inputs,
otherwise high.
INVALID2
Inductor/Diode Connection PointLX
1
FUNCTIONNAME
______________________________________________________________Pin Description
™ LapLink is a trademark of Traveling Software, Inc.
AutoShutdown is a trademark of Maxim Integrated Products.
MAX3218
Diode Selection
Key diode specifications are fast recovery time (<10ns),
average current rating (>100mA), and peak current rat-
ing (>350mA). Inexpensive fast silicon diodes, such as
the 1N6050, are generally recommended. More expen-
sive Schottky diodes improve efficiency and give slightly
better performance at very low V CC voltages. Table 1
lists suppliers of both surface-mount and through-hole
diodes. 1N914s are usually satisfactory, but specifica -
tions and performance vary widely with different manu-
facturers.
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 deter -
mine both the ripple and the absolute voltage of V-.
Bypass VCC to GND with at least 1 µF (C4) placed close
to pins 5 and 6. If the V CC line is not bypassed else -
where (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 fre-
quency of the power supplies (about 250kHz). If alu-
minum electrolytics are used, higher capacitance
values may be required.
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
6 _______________________________________________________________________________________
MANUFACTURER PHONEPART NUMBER FAX
USA (814) 237-1431LQH4N150K-TAMurata-Erie USA (814) 238-0490
USA (708) 956-0666
Japan (03) 3607-5111
CD43150Sumida USA (708) 956-0702
Japan (03) 3607-5428
USA (508) 853-5000TMPD6050LTAllegro USA (508) 853-7556
USA (708) 803-6100
Japan (03) 3278-5111
NLC453232T-150KTDK USA (708) 803-6296
Japan (03) 3278-5358
USA (516) 435-1110CMPSH-3 (Schottky)Central Semiconductor USA (516) 435-1824
USA (408) 749-0510MMBD6050LT1 (silicon)Motorola USA (408) 991-7420
USA (401) 762-3800PMBD6050 (silicon)Philips USA (401) 767-4493
USA (408) 749-05101N6050 (silicon),
1N5817 (Schottky)
Motorola USA (408) 991-7420
Table 1. Suggested Component Suppliers
GND
T2
T1
T2OUT
R1IN
R2IN
T1OUT
C1-
C1+
V-
T2IN
R1OUT
R2OUT
T1IN 14
18
C3
1µF
C1
0.47µF
C4
1µFC2
1µF
16
15
13
12
11
5, 17, 20
VCC
3
61
19
4
2
7
8
9
10
1.8V to
4.25V
LX
15µH 1N6050
V+
FORCEON
INVALID
FORCEOFF
5k
5k
R1
R2
MAX3218
Figure 1. Typical Operating Circuit
Inductors
Diodes—Surface-Mount
Diodes—Through-Hole
RS-232 Drivers
The two drivers are identical, and deliver EIA/TIA-232E
and EIA/TIA-562 output voltage levels when V CC is
between 1.8V and 4.25V. One transmitter can drive up
to 3kΩin parallel with 2500pF at up to 120kbps.
Connect unused drivers to either GND or V CC. When
FORCEOFF is driven low, or when AutoShutdown circuit-
ry 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-to-
rail. Receivers are disabled only when FORCEON and
FORCEOFF inputs are low. (See Table 2.)
Shutdown
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.
AutoShutdown™
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 con -
nected peripheral transmitters are turned off. The sys -
tem 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 cir-
cuitry 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
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
_______________________________________________________________________________________ 7
Table 3. AutoShutdown Logic
LHNo Normal Operation (Forced On)
LHNo Shutdown (AutoShutdown)
HLYes Shutdown (Forced Off)
LLNo Shutdown (Forced Off)
HHYes Normal Operation
RS-232 SIGNAL
PRESENT AT
RECEIVER INPUT INVALID OUTPUTFORCEOFF INPUT TRANSCEIVER STATUSFORCEON INPUT
H
L
X
X
X
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
CPU
I/O
CHIP
WITH
UART
MAX3218
RS-232
FORCEOFF
FORCEON
INVALID
Figure 2. Interface Under Control of PMU
Table 2. Receiver Status
FORCEON FORCEOFF RECEIVER STATUS
Receiver Enabled
Receiver Disabled
XH
LL
HX
MAX3218
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. If the other system outputs
valid RS-232 signals within that time, the RS-232 ports on
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 simulta-
neously 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 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.
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 volt-
age rather than suffer the losses of a regulator or DC-
DC converter. If this is not possible, but your system is
powered from two cells and employs a 3V DC-DC con-
verter 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 logic-
level compatibility with the 3V logic.
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
8 _______________________________________________________________________________________
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.
FORCEOFF
0
0
0
0
1
1
1
1
FORCEON
0
0
1
1
0
0
1
1
INVALID
0
1
0
1
0
1
0
1
POWER DOWN
0
0
0
0
0
1
1
1
POWER DOWN
FORCEOFF
FORCEON
INVALID
+
-
+
-
RxR_IN
FORCEON
FORCEOFF
R_OUT
30µs
DELAY
•
•
•
•
•
•
+0.3V to +2.8V
-0.3V to -2.8V
Figure 3. AutoShutdown Logic
Keep communications cables short to minimize capaci-
tive loading. Lowering the capacitive loading on the
transmitter outputs reduces the MAX3218’s power con-
sumption. 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 transmit-
ters deliver at least 5V to receivers with impedances
that can be as low as 3k Ω. 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
3kΩreceiver loads, the total power consumption is con-
siderably 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 produc-
ing EIA/TIA-562 levels.
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
_______________________________________________________________________________________ 9
TRANSMITTERS ENABLED, INVALID HIGH
AUTOSHUTDOWN, TRANSMITTERS DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
TRANSMITTERS ENABLED, INVALID HIGH
-2.8V
-0.3V
+2.8V
AUTOSHUTDOWN RECEIVER INPUT THRESHOLD (V)
+0.3V
(a)
(b)
0V
INDETERMINATE
INDETERMINATE
V-
VCC
0V
V+
0
VCC
tINVL
tWU
INVALID
REGION
RECEIVER
INPUT
VOLTAGE
(V)
INVALID
OUTPUT
(V)
tINVH
Figure 4. AutoShutdown Trip Levels Figure 5. AutoShutdown with Initial Turn-On to Wake Up a
System
FORCEON
MASTER SHDN LINE
0.1µF 1M
FORCEOFF
MAX3218
POWER
MANAGEMENT
UNIT
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
10 ______________________________________________________________________________________
Figure 6. Operating from Unregulated and Regulated Supplies
VCC LX
61V+
19
C4
0.1µF
C5
1µF
1µF
C2
15µH1N6050
3V
DC-DC
CONVERTER
MAX878
OR
MAX756
OR
MAX856
GND
T2
T1
T2OUT
R1IN
R2IN
T1OUT
C1-
C1+
V-
T2IN
R1OUT
R2OUT
T1IN 14
18
C1
0.47µF
C3
1µF
16
15
13
12
11
5, 17, 20
3
4
2
7
8
9
10
FORCEON
INVALID
FORCEOFF
5k
5k
R1
R2
MAX3218
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
______________________________________________________________________________________ 11
_____+3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim
0.1µF capacitors, AutoShutdown,
complementary receiver,
drives mice
23212013/53.0 to 5.5MAX3243
0.1µF capacitors23212022/23.0 to 5.5MAX3222
0.1µF capacitors56212022/23.0 to 3.6MAX563
Wide supply range56223053/52.7 to 5.25MAX562
Pin-compatible with MAX214
562
232
232
232
562120
232
EIA/TIA-
232
OR 562
3.0 to 3.6 Pin-compatible with MAX21312024/5
0
MAX560
4/53.0 to 3.6MAX561
Pin-compatible with MAX232232
Same as MAX218 but with
AutoShutdown
12022/21.8 to 4.25MAX3218
AutoShutdown, complementary
receiver, drives mice, transient
detection
12053/52.7 to 3.6MAX3212
No. OF
RECEIVERS
ACTIVE IN
SHUTDOWN
SUPPLY
VOLTAGE
(V)
Operates directly from a battery
without a voltage regulator
12022/21.8 to 4.25MAX218
12022/23.0 to 5.5MAX3232
AutoShutdown, 0.1µF capacitors23212022/23.0 to 5.5MAX3223
Drives mice12053/53.0 to 3.6MAX212
FEATURES
GUAR-
ANTEED
DATA
RATE
(kbps)
No. OF
TRANSMITTERS/
RECEIVERS
PART
0.1µF capacitors, 2 complemen-
tary receivers, drives mice
23212053/53.0 to 5.5MAX3241
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
__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
________________________________________________________Package Information
L
DIM
A
A1
B
C
D
E
e
H
L
α
DIM
D
D
D
D
D
MIN
0.068
0.002
0.010
0.004
0.205
0.301
0.025
0˚
MIN
0.239
0.239
0.278
0.317
0.397
MAX
0.078
0.008
0.015
0.008
0.209
0.311
0.037
8˚
MAX
0.249
0.249
0.289
0.328
0.407
MIN
1.73
0.05
0.25
0.09
5.20
7.65
0.63
0˚
MIN
6.07
6.07
7.07
8.07
10.07
MAX
1.99
0.21
0.38
0.20
5.38
7.90
0.95
8˚
PINS
14
16
20
24
28
MAX
6.33
6.33
7.33
8.33
10.33
INCHES
INCHES
MILLIMETERS
MILLIMETERS
α
SSOP
SHRINK
SMALL OUTLINE
PACKAGE
HE
D
A
A1
C
B
0.65 BSC0.0256 BSC
21-0056A
e
SEE VARIATIONS
___________________Chip Topography
C1+
GND
T1OUT
FORCEON
FORCEOFF
T2OUT
GND
T1IN
LX
INVALID V+
R2IN
R1OUT
T2IN R2OUT
0.101"
(2.565mm)
0.122"
(3.099mm)
R1IN
C1-
V-
GND
VCC
TRANSISTOR COUNT: 571
SUBSTRATE CONNECTED TO GND
