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MAX3218
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
General Description
Features
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.
BETTER THAN BIPOLAR!
Applications
Battery-Powered Equipment
Subnotebook Computers
PDAs
o 1µA Supply Current Using AutoShutdown
o Operates Directly from Two Alkaline,
NiCd or NiMH Cells
o +1.8V to +4.25V Single-Supply Voltage Range
o 120kbps Data Rate Guaranteed
o Low-Cost Surface-Mount Components
o Meets EIA/TIA-232E Specifications
o Three-State Receiver Outputs
o Flow-Through Pinout
o On-Board DC-DC Converters
o 20-Pin SSOP and DIP Packages
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX3218CPP+
MAX3218CAP+
MAX3218EAP+
0ºC to +70ºC
0ºC to +70ºC
-40ºC to +85ºC
20 Plastic DIP
20 SSOP
20 SSOP
+Denotes a lead(Pb)-free/RoHS-compliant package.
Pin Configuration
TOP VIEW
+
LX 1
20 GND
INVALID 2
19 V+
FORCEON 3
18 C1+
FORCEOFF 4
17 GND
Hand-Held Equipment
GND 5
Peripherals
VCC 6
15 V-
Cellular Phones
T1IN 7
14 T1OUT
T2IN 8
13 T2OUT
AutoShutdown is a trademark of Maxim Integrated Products.
19-0380; Rev 2; 5/18
MAX3218
16 C1-
R1OUT 9
12 R1IN
R2OUT 10
11 R2IN
DIP/SSOP
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
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 ................................................................-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
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.
Electrical Characteristics
(Circuit of Figure 1, VCC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at VCC = 3.0V, TA = +25°C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
4.25
V
DC CHARACTERISTICS
Operating Voltage Range
1.8
Supply Current, AutoShutdown™
VCC = 3.0V, TA = +25°C, all R_IN open,
FORCEON = GND, FORCEOFF = VCC
1.0
10
µA
Supply Current, Shutdown
FORCEOFF = GND, TA = +25°C, VCC = 3.0V
1.0
10
µA
Supply Current,
AutoShutdown™ Disabled
FORCEON = FORCEOFF = VCC = 3.0V, no load
2.0
3.0
mA
0.33 x VCC
V
±1
µA
0.4
V
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
T_IN, FORCEON, FORCEOFF
Input Logic Threshold High
T_IN, FORCEON, FORCEOFF
Input Leakage Current
T_IN, FORCEON = FORCEOFF = 0V or VCC
Output Voltage Low
R_OUT, IOUT = 1.0mA
Output Voltage High
R_OUT, IOUT = -0.4mA
Output Leakage Current
R_OUT, 0V ≤ R_OUT ≤ VCC,
FORCEON = FORCEOFF = 0V
0.67 x VCC
V
0.001
VCC - 0.25
VCC - 0.08
0.05
V
±10
µA
AUTOSHUTDOWN (FORCEON = GND, FORCEOFF = VCC)
Positive threshold
Negative threshold
Receiver Input Thresholds,
Transmitters Enabled
Figure 4a
Receiver Input Thresholds
Transmitters Disabled
1µA supply current, Figure 4a
INVALID Output Low Voltage
IOUT = 1.0mA, -0.3V < R_IN < 0.3V
INVALID Output High Voltage
IOUT = -0.4mA, |R_IN| > 2.8V
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2.8
-2.8
-0.3
VCC - 0.25
V
0.3
V
0.4
V
V
Maxim Integrated | 2
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
Electrical Characteristics (continued)
(Circuit of Figure 1, VCC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at VCC = 3.0V, TA = +25°C.)
PARAMETER
CONDITIONS
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 3.6V
2.8
Input Hysteresis
Input Resistance
0.7
-15V < R_IN < 15V
3
5
±6
V
V
7
kΩ
EIA/TIA-232E TRANSMITTER OUTPUTS
Output Voltage Swing
All transmitter outputs loaded with 3kΩ to ground
±5
Output Resistance
VCC = 0V, -2V < T_OUT < 2V
300
V
Ω
Output Short-Circuit Current
±24
±100
mA
Timing Characteristics
(Circuit of Figure 1, VCC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at VCC = 3.0V, TA = +25°C.)
PARAMETER
SYMBOL
Data Rate
CONDITIONS
MIN
TYP
2500pF || 3kΩ load each transmitter, one transmitter switching, 150pF load each receiver
120
235
MAX
UNITS
kbps
Receiver Output Enable Time
tER
90
300
ns
Receiver Output Disable Time
tDR
200
500
ns
Transmitter Output Enable Time
tET
250
450
µs
Transmitter Output Disable Time
Receiver Propagation Delay
Transmitter Propagation Delay
tDT
500
ns
tPHLR
150pF load
290
1000
tPLHR
150pF load
260
1000
tPHLT
2500pF || 3kΩ load
1.9
2.7
tPLHT
2500pF || 3kΩ load
1.8
2.7
TA = +25°C, VCC = 3.0V, RL = 3kΩ to 7kΩ,
CL = 50pF to 2500pF, measured from
+3V to -3V or -3V to +3V
Transition Region Slew Rate
3.0
30
ns
µs
V/µs
AUTOSHUTDOWN TIMING
Receiver Threshold to
Transmitters Enabled
tWU
Figure 4b
250
µs
Receiver Positive or Negative
Threshold to INVALID High
tINVH
Figure 4b
1
µs
Receiver Positive or Negative
Threshold to INVALID Low
tINVL
Figure 4b
30
µs
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Maxim Integrated | 3
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
Typical Operating Characteristics
(Circuit of Figure 1, VCC = 1.8V, all transmitter outputs loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
TRANSMITTING SUPPLY CURRENT
vs. LOAD CAPACITANCE
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
SUPPLY CURRENT (mA)
VCC = 2.4V
90
100
240kbps
80
60
120kbps
40
20kbps
20
0kbps
MAX3218-02
120
100
SUPPLY CURRENT (mA)
1 TRANSMITTER FULL DATA RATE
1 TRANSMITTER 1/8 DATA RATE
RL = 3kΩ + 2500pF
MAX3218-01
140
80
235kbps
TRANSMITTER 1 OPERATING
AT SPECIFIED BIT RATE,
TRANSMITTER 2 OPERATING
AT 1/16 THAT RATE.
70
60
120kbps
50
40
20kbps
30
20
0
2.4
1.8
3.0
3.6
1000
0
4.2
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
SUPPLY VOLTAGE (V)
TIME TO EXIT SHUTDOWN
(ONE TRANSMITTER HIGH,
ONE TRANSMITTER LOW)
FORCEON, FORCEOFF
VOH
2V/div
T_OUT
VCC = 1.8V
RL = 3kΩ || 2500pF
VOL
100μs/div
TRANSMITTER OUTPUT VOLTAGE vs.
LOAD CAPACITANCE AT 120kbps
6
MAX3218-05
12
MAX3218-04
10
VOUT+
4
SLEW RATE (V/μs)
TRANSMITTER OUTPUT VOLTAGE (V)
8
SLEW RATE vs.
TRANSMITTER CAPACITANCE
2
0
-2
+SLEW
8
-SLEW
6
4
DATA RATE 120kbps,
TRANSMITTERS LOADED WITH
3kΩ PLUS INDICATED CAPACITANCE
-4
VOUT-
2
-6
0
-8
0
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
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5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
Maxim Integrated | 4
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
Pin Description
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.
7, 8
T1IN, T2IN
Transmitter Inputs
9, 10
R1OUT, R2OUT
Receiver Outputs
11, 12
R2IN, R1IN
13, 14
T2OUT, T1OUT
15
V-
Negative Supply generated on-board
16, 18
C1-, C1+
Terminal for Charge-Pump Capacitor
19
V+
Positive Supply generated on-board
Inductor/Diode Connection Point
Output of Invalid Signal Detector. Low if invalid RS-232 levels are present on all receiver inputs,
otherwise high.
Receiver Inputs
Transmitter Outputs, swing between V+ and V-
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.
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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.
Maxim Integrated | 5
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
Table 1. Suggested Component Suppliers
MANUFACTURER
PART NUMBER
PHONE
FAX
Inductors
Murata-Erie
LQH4N150K-TA
USA (814) 237-1431
USA (814) 238-0490
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) 853-7556
Central Semiconductor
CMPSH-3 (Schottky)
USA (516) 435-1110
USA (516) 435-1824
Motorola
MMBD6050LT1 (silicon)
USA (408) 749-0510
USA (408) 991-7420
Philips
PMBD6050 (silicon)
USA (401) 762-3800
USA (401) 767-4493
1N6050 (silicon),
1N5817 (Schottky)
USA (408) 749-0510
USA (408) 991-7420
Diodes—Surface-Mount
Diodes—Through-Hole
Motorola
Diode Selection
Key diode specifications are fast recovery time (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 VCC voltages. 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 VCC to GND with at least 1µF (C4) placed close
to pins 5 and 6. If the VCC line 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
15μH
C4
1μF
6
VCC
3
4
2
1N6050
1
LX
C2
1μF
19
V+
V-
FORCEON
MAX3218
C1+
FORCEOFF
C1-
INVALID
7 T1IN
8 T2IN
9 R1OUT
15
C3
1μF
18
16
C1
0.47μF
T1OUT 14
T1
T2OUT 13
T2
R1IN 12
R1
5kΩ
10 R2OUT
R2IN 11
R2
5kΩ
GND
5, 17, 20
Figure 1. Typical Operating Circuit
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Maxim Integrated | 6
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
Table 2. Receiver Status
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEOFF
FORCEON
INVALID
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. Supply current is minimized
when the receiver inputs are static in any one of three
states: floating (ground), GND, or VCC.
AutoShutdown
Figure 2. Interface Under Control of PMU
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 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.)
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
Table 3. AutoShutdown Logic
RS-232 SIGNAL
PRESENT AT
RECEIVER INPUT
FORCEOFF INPUT
FORCEON INPUT
INVALID OUTPUT
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)
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TRANSCEIVER STATUS
Maxim Integrated | 7
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
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
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
+0.3V to +2.8V
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 VCC (C4) and at
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.
+
FORCEOFF
POWER DOWN
+
-0.3V to -2.8V
FORCEON
R_IN
Rx
R_OUT
•
•
FORCEON
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.
•
30µs
DELAY
INVALID
•
•
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
Figure 3. AutoShutdown Logic
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Maxim Integrated | 8
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
AUTOSHUTDOWN RECEIVER INPUT THRESHOLD (V)
MAX3218
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
IA/TIA-562 Standards
TRANSMITTERS ENABLED, INVALID HIGH
+2.8V
INDETERMINATE
+0.3V
0V
AUTOSHUTDOWN, TRANSMITTERS DISABLED,
1μA SUPPLY CURRENT, INVALID LOW
-0.3V
INDETERMINATE
-2.8V
TRANSMITTERS ENABLED, INVALID HIGH
(a)
RECEIVER
INPUT
VOLTAGE
(V)
INVALID
REGION
VCC
INVALID
OUTPUT
(V)
0
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.
POWER
MANAGEMENT
UNIT
MASTER SHDN LINE
0.1µF
tINVL
1M
tINVH
V+
VCC
0V
FORCEOFF FORCEON
VtWU
MAX3218
(b)
Figure 4. AutoShutdown Trip Levels
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Figure 5. AutoShutdown with Initial Turn-On to Wake Up a
System
Maxim Integrated | 9
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
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
FORCEOFF
C1+
C1
0.47μF
MAX3218
INVALID
7 T1IN
8 T2IN
9 R1OUT
18
C1- 16
T1OUT 14
T1
T2OUT 13
T2
R1IN 12
R1
5kΩ
10
R2OUT
R2IN 11
R2
5kΩ
GND
5, 17, 20
Figure 6. Operating from Unregulated and Regulated Supplies
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Maxim Integrated | 10
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
+3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim
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 4.25
2/2
2
120
232
Same as MAX218 but with
AutoShutdown
MAX560
3.0 to 3.6
4/5
2
120
562
Pin-compatible with MAX213
MAX561
3.0 to 3.6
4/5
0
120
562
Pin-compatible with MAX214
MAX562
2.7 to 5.25
3/5
5
230
562
Wide supply range
MAX563
3.0 to 3.6
2/2
2
120
562
0.1µF capacitors
MAX3222
3.0 to 5.5
2/2
2
120
232
0.1µF capacitors
MAX3223
3.0 to 5.5
2/2
2
120
232
AutoShutdown, 0.1µF capacitors
MAX3232
3.0 to 5.5
2/2
2
120
232
Pin-compatible with MAX232
MAX3241
3.0 to 5.5
3/5
5
120
232
0.1µF capacitors, 2 complementary receivers, drives mice
MAX3243
3.0 to 5.5
3/5
1
120
232
0.1µF capacitors, AutoShutdown,
complementary receiver,
drives mice
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FEATURES
Maxim Integrated | 11
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
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
0.078
1.73
1.99
0.002
0.008
0.05
0.21
0.010
0.015
0.25
0.38
0.004
0.008
0.09
0.20
SEE VARIATIONS
0.205
0.209
5.20
5.38
0.0256 BSC
0.65 BSC
0.301
0.311
7.65
7.90
0.025
0.037
0.63
0.95
0˚
8˚
0˚
8˚
DIM PINS
e
A
B
A1
SSOP
SHRINK
SMALL OUTLINE
PACKAGE
D
D
D
D
D
14
16
20
24
28
INCHES
MILLIMETERS
MAX
MIN MAX MIN
6.33
0.239 0.249 6.07
6.33
0.239 0.249 6.07
7.33
0.278 0.289 7.07
8.33
0.317 0.328 8.07
0.397 0.407 10.07 10.33
21-0056A
D
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Maxim Integrated | 12
1μA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown
MAX3218
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
3/95
Initial release
—
1
4/18
Added lead-free designation to part numbers in Ordering Information
1
2
5/18
Removed MAX3218C/D and MAX3218EPP+ from Ordering Information
1
DESCRIPTION
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and
max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2018 Maxim Integrated Products, Inc. | 13
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