_______________General Description
The MAX3221/MAX3223/MAX3243 achieve 1µA supply
current with Maxim’s revolutionary AutoShutdown™ feature. When the MAX3221/MAX3223/MAX3243 do not
sense a valid signal level on their 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 any RS-232 receiver input. As a result, the system
saves power without changes to the existing BIOS or
operating system.
The MAX3221/MAX3223/MAX3243 transceivers are 3Vpowered EIA/TIA-232 and V.28/V.24 communications
interfaces intended for notebook computer applications. A proprietary, high-efficiency, dual charge-pump
power supply and a low-dropout transmitter combine to
deliver true RS-232 performance from a single +3.0V to
+5.5V supply. A guaranteed data rate of 120kbps provides compatibility with popular software for communicating with personal computers.
The MAX3221/MAX3223/MAX3243 require only 0.1µF
capacitors in 3.3V operation, and can operate from input
voltages ranging from +3.0V to +5.5V. They are ideal for
3.3V-only systems, mixed 3.3V and 5.0V systems, or
5.0V-only systems that require true RS-232 performance.
The MAX3221 is a 1-driver/1-receiver 16-pin SSOP version of the 20-pin MAX3223 (2-driver/2-receiver). The
MAX3243 3-driver/5-receiver, complete serial port is
ideal for notebook or subnotebook computers. The
MAX3243 includes one complementary always-active
receiver. This receiver can monitor an external device
(such as a modem) in shutdown, without forward biasing the protection diodes in a UART that may have V
CC
completely removed.
____________________________Features
♦ 1µA Supply Current Achieved with AutoShutdown
♦ Small 0.1µF Capacitors
♦ True RS-232 Operation from V
CC
= +3.0V to +5.5V
♦ Meets EIA/TIA-562 Specifications Down to 2.7V
♦ Guaranteed 120kbps Data Rate
♦ 6V/µs Min Guaranteed Slew Rate
♦ Smallest Single-Supply RS-232 Transceiver
(MAX3221)
♦ Guaranteed Mouse Driveability (MAX3243)
♦ Small TSSOP Package (MAX3223/MAX3243)
________________________Applications
Notebook, Subnotebook, and Palmtop Computers
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
Printers
MAX3221/MAX3223/MAX3243*
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
________________________________________________________________ Maxim Integrated Products 1
19-0306; Rev 6; 3/99
PART
MAX3221CAE
MAX3221EUE†
-40°C to +85°C
0°C to +70°C
TEMP. RANGE PIN-PACKAGE
16 SSOP
16 TSSOP
* Covered by U.S. Patent numbers 4,636,930; 4,679,134; 4,777,577; 4,797,899; 4,809,152; 4,897,774; 4,999,761; and other patents pending.
†Future product—contact factory for availability.
AutoShutdown is a trademark of Maxim Integrated Products.
Pin Configurations appear at end of data sheet.
Typical Operating Circuits appear at end of data sheet.
MAX3223EPP -40°C to +85°C 20 Plastic DIP
MAX3223EAP -40°C to +85°C 20 SSOP
MAX3243CWI
0°C to +70°C 28 Wide SO
MAX3243CAI 0°C to +70°C 28 SSOP
MAX3243EWI -40°C to +85°C 28 Wide SO
MAX3243EAI -40°C to +85°C 28 SSOP
MAX3223CPP
MAX3223CAP 0°C to +70°C
0°C to +70°C 20 Plastic DIP
20 SSOP
______________Ordering Information
_____________________Selector Guide
MAX3221
MAX3223
MAX3243
1
2
3
1
2
3.0 to 5.5
3.0 to 5.5
3.0 to 5.55
Yes
Yes
Yes
PART Tx Rx VCCRANGE (V) AutoShutdown
MAX3221CUE†
0°C to +70°C 16 TSSOP
MAX3221EAE -40°C to +85°C 16 SSOP
MAX3223CUP 0°C to +70°C 20 TSSOP
MAX3223EUP -40°C to +85°C 20 TSSOP
MAX3243CUI 0°C to +70°C 28 TSSOP
MAX3243EUI -40°C to +85°C 28 TSSOP
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at 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.
VCC...........................................................................-0.3V to +6V
V+ (Note 1) ...............................................................-0.3V to +7V
V- (Note 1) ...............................................................+0.3V to -7V
V+ +
|V-
| (Note 1).................................................................+13V
Input Voltages
T_IN, FORCEOFF, FORCEON, EN (MAX3223) ......-0.3V to +6V
R_IN ...................................................................................±25V
Output Voltages
T_OUT.............................................................................±13.2V
R_OUT, INVALID ......................................-0.3V to (V
CC
+ 0.3V)
Short-Circuit Duration
T_OUT ......................................................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
16-Pin SSOP (derate 7.14mW/°C above +70°C) ...........571mW
16-Pin TSSOP (derate 6.70mW/°C above +70°C) .........533mW
20-Pin Plastic DIP (derate 11.11mW/°C above +70°C)....889mW
20-Pin SSOP (derate 8.00mW/°C above +70°C) ...........640mW
20-Pin TSSOP DIP (derate 7.00mW/°C above +70°C).....559mW
28-Pin Wide SO (derate 12.50mW/°C above +70°C) ............1W
28-Pin SSOP (derate 9.52mW/°C above +70°C) ...........762mW
28-Pin TSSOP (derate 8.70mW/°C above +70°C) .........696mW
Operating Temperature Ranges
MAX32_ _C_ _.......................................................0°C to +70°C
MAX32_ _E_ _....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Note 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V.
I
OUT
= 1.6mA
Receivers disabled
T_IN, EN, FORCEON, FORCEOFF
T_IN, EN, FORCEON, FORCEOFF
T_IN, FORCEON, FORCEOFF, EN (MAX3223)
I
OUT
= -1.0mA
CONDITIONS
VVCC- 0.6 VCC- 0.1Output Voltage High
V0.4Output Voltage Low
µA±0.05 ±10Output Leakage Current
µA±0.01 ±1.0Input Leakage Current
V
2.4
Input Logic Threshold High
µA1.0 10
V0.8Input Logic Threshold Low
UNITSMIN TYP MAXPARAMETER
VCC= 3.3V
VCC= 5.0V
2.0
Supply Current, AutoShutdown
Supply Current, Shutdown µA1.0 10
Supply Current,
AutoShutdown Disabled
VCC= 3.3V
or 5.0V,
T
A
= +25°C
mA0.3 1.0
2.7
Receiver Positive or Negative
Threshold to INVALID High (t
INVH
)
Figure 5 µs1
Receiver Threshold to
Transmitters Enabled (t
WU
)
Figure 5 µs250
Receiver Positive or Negative
Threshold to INVALID Low (t
INVL
)
Figure 5 µs30
Receiver Input Thresholds to
Transmitters Enabled
Figure 5 V
-2.7
INVALID Output Voltage Low
I
OUT
= 1.6mA V0.4
Receiver Input Thresholds to
Transmitters Disabled
1µA supply current, Figure 5 V-0.3 0.3
Positive threshold
Negative threshold
INVALID Output Voltage High
I
OUT
= -1.0mA VVCC- 0.6
DC CHARACTERISTICS
LOGIC INPUTS AND RECEIVER OUTPUTS
AUTOSHUTDOWN (FORCEON = GND, FORCEOFF = VCC)
All R_IN open, FORCEON = GND,
FORCEOFF = V
CC
FORCEOFF = GND
FORCEON = FORCEOFF = VCC,
no load
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC= +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at TA= +25°C.)
Note 2: C1–C4 = 0.1µF, tested at 3.3V ±10%. C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%.
200
Normal operation 200
Receiver Output Enable Time Normal operation ns
t
PLH
Receiver input to receiver output,
CL= 150pF
4 8.0 30
Transition-Region Slew Rate V/µs
VCC= 3.3V,
RL= 3kΩ to 7kΩ,
TA= +25°C,
measured from +3V to
-3V or -3V to +3V
Transmitter Skew
200
ns
t
PHL
- t
PLH
PARAMETER MIN TYP MAX UNITS
±25
Output Short-Circuit Current ±35 ±60 mA
Output Resistance 300 10M Ω
Output Leakage Current µA
Input Threshold Low
0.6 1.2
V
±5.0 ±5.4Output Voltage Swing V
Maximum Data Rate 120 235 kbps
Receiver Propagation Delay
0.3
µs
CONDITIONS
VCC= V+ = V- = 0V, transmitter output = ±2V
V
OUT
= ±12V, VCC= 0V or 3.0V to 5.5V,
transmitters disabled
RL= 3kΩ, CL= 1000pF, one transmitter switching
All transmitter outputs loaded with 3kΩ to ground
nsReceiver Output Disable Time
t
PHL
0.3
Input Voltage Range -25 25 V
Input Hysteresis 0.3 V
Input Threshold High V
Input Resistance 35 7kΩTA= +25°C
0.8 1.5
1.8 2.4
1.5 2.4
TA= +25°C
TA= +25°C
VCC= 3.3V
VCC= 3.3V
VCC= 5.0V
VCC= 5.0V
CL= 200pF to 2500pF
CL= 200pF to 1000pF 630
±5Transmitter Output Voltage V
T1IN = T2IN = GND, T3IN = VCC,
T3OUT loaded with 3kΩ to GND, T1OUT and
T2OUT loaded with 2.5mA each
MAX3221/MAX3223
MAX3243
200 1000
Receiver Skew
100
ns
t
PHL
- t
PLH
MAX3221/MAX3223
MAX3243
100 500
RECEIVER INPUTS
TIMING CHARACTERISTICS
TRANSMITTER OUTPUTS
MOUSE DRIVEABILITY (MAX3243)
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
4 _______________________________________________________________________________________
__________________________________________Typical Operating Characteristics
(VCC= +3.3V, 235kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA= +25°C, unless otherwise noted.)
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
0
MAX3221/MAX3223
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3221/3223-01
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
2000 30001000 4000 5000
V
OUT+
V
OUT-
0
2
4
6
8
10
12
14
16
18
20
22
150 500
MAX3221/MAX3223
SLEW RATE
vs. LOAD CAPACITANCE
MAX3221/3223-02
LOAD CAPACITANCE (pF)
SLEW RATE (V/µs)
2000 30001000 4000 5000
FOR DATA RATES UP TO 235kbps
+SLEW
-SLEW
5
10
15
20
25
30
35
40
0
5
10
15
20
25
30
35
0
MAX3221/MAX3223
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
MAX3221/3223-03
LOAD CAPACITANCE (pF)
MAX3223 SUPPLY CURRENT (mA)
MAX3221 SUPPLY CURRENT (mA)
2000 30001000 4000 5000
235kbps
120kbps
20kbps
-7.5
-5.0
-2.5
0
2.5
5.0
7.5
0
MAX3243
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3221/3223-04
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
2000 30001000 4000 5000
V
OUT
+
1 TRANSMITTER AT 235kbps
2 TRANSMITTERS AT 30kbps
V
OUT
-
ALL OUTPUTS LOADED WITH 3kΩ +CL
0.1µF CHARGE-PUMP CAPACITORS
FOR ALL DATA RATES UP TO 235kbps
4
6
8
10
12
14
16
18
20
22
24
0
MAX3243
SLEW RATE
vs. LOAD CAPACITANCE
MAX3221/3223-05
LOAD CAPACITANCE (pF)
SLEW RATE (V/µs)
2000 30001000 4000 5000
+SLEW
-SLEW
0
5
10
15
20
25
30
35
45
40
0
MAX3243
SUPPLY CURRENT vs. LOAD
CAPACITANCE WHEN TRANSMITTING DATA
MAX3221/3223-06
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
2000 30001000 4000 5000
235kbps
120kbps
20kbps
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
_______________________________________________________________________________________ 5
______________________________________________________________Pin Description
Noninverting Receiver Output—active in shutdownR2OUTB
Output of the valid signal detector. Indicates if a valid RS-232 level is present on receiver inputs logic “1”.
INVALID
Drive low to shut down transmitters and on-board power supply. This overrides all automatic circuitry and FORCEON (Table 1).
FORCEOFF
Drive high to override automatic circuitry keeping transmitters on
(FORCEOFF must be high) (Table 1).
FORCEON
Negative terminal of the voltage doubler charge-pump capacitorC1-
RS-232 Receiver InputsR_IN
RS-232 Transmitter OutputsT_OUT
TTL/CMOS Transmitter InputsT_IN
TTL/CMOS Receiver OutputsR_OUT
-5.5V generated by the charge pumpV-
Negative terminal of inverting charge-pump capacitorC2-
Positive terminal of inverting charge-pump capacitorC2+
Receiver Enable Control. Drive low for normal operation. Drive high to force
the receiver outputs into a high-Z state.
EN
FUNCTION
GroundGND
+3.0V to +5.5V Supply VoltageV
CC
LapLink is a trademark of Traveling Software.
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3221/MAX3223/MAX3243’s internal power
supply consists of a regulated dual charge pump that
provides output voltages of +5.5V (doubling charge
pump) and -5.5V (inverting charge pump), regardless
of the input voltage (VCC) over the +3.0V to +5.5V
range. The charge pumps operate in a discontinuous
mode: if the output voltages are less than 5.5V, the
charge pumps are enabled; if the output voltages
exceed 5.5V, the charge pumps are disabled. Each
charge pump requires a flying capacitor (C1, C2) and
a reservoir capacitor (C3, C4) to generate the V+ and
V- supplies.
RS-232 Transmitters
The transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. They
guarantee a 120kbps data rate with worst-case loads of
3kΩ in parallel with 1000pF, providing compatibility with
PC-to-PC communication software (such as Laplink™).
Typically, the MAX3221/MAX3223/MAX3243 can operate at data rates of 235kbps. Transmitters can be paralleled to drive multiple receivers or mice (MAX3243).
Figure 1 shows a complete system connection.
When FORCEOFF is driven to ground, or the AutoShutdown circuitry senses invalid voltage levels at all
receiver inputs, the transmitters are disabled and the
outputs are forced into a high-impedance state.
—
10
16
12
4
8
13
11
9
7
6
5
1
14
15
NAME
MAX3221
+5.5V generated by the charge pumpV+3
Positive terminal of the voltage doubler charge-pump capacitorC1+2
—
11
20
14
4
9, 16
8, 17
12, 13
10, 15
7
6
5
1
18
19
20
21
22
23
24
4–8
9, 10, 11
12, 13, 14
15–19
3
2
1
—
25
26
MAX32233MAX3243
27
2 28
PIN
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
6 _______________________________________________________________________________________
RS-232 Receivers
The MAX3221/MAX3223/MAX3243’s receivers convert
RS-232 signals to CMOS-logic output levels. All
receivers have one inverting three-state output. In shutdown (FORCEOFF = low) or in AutoShutdown, the
MAX3221/MAX3223’s receivers are active (Table 1).
Driving EN high places the receiver(s) in a high-impedance state. The MAX3243’s receivers are high impedance when the part is shut down.
The MAX3243 has an always-active complementary
output (R2OUTB). R2OUTB is an extra output that monitors receiver activity while the other receivers are high
impedance. This allows Ring Indicator to be monitored
without forward biasing other devices connected to the
receiver outputs. This is ideal for systems where V
CC
is
set to 0V in shutdown to accommodate peripherals,
such as UARTs (Figure 2).
Figure 1. Interface Under Control of PMU
Figure 2. The MAX3243 detects RS-232 activity when the
UART and interface are shut down.
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEOFF
FORCEON
INVALID
MAX3243
V
I/O
CPU
CHIP
WITH
UART
RS-232
(a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
CC
UART
GND
PROTECTION
DIODE
Rx
Tx
TO
µP
TRANSITION
DETECTOR
SHDN = GND
LOGIC
V
CC
PREVIOUS
RS-232
I
5k
V
CC
PROTECTION
DIODE
V
CC
Rx
UART
I
R2OUTB
R2OUT
THREE-STATED
GND
Tx
FORCEOFF = GND
T1IN
(b) NEW MAX3243: IN SHUTDOWN, R2OUTB IS USED TO MONITOR EXTERNAL
DEVICES AND R2OUT IS THREE STATED, ELIMINATING A CURRENT PATH
THROUGH THE UART'S PROTECTION DIODE.
MAX3243
R2IN
5k
T1OUT
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
_______________________________________________________________________________________ 7
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
MAX3221/MAX3223/MAX3243 sense no valid signal
levels on all receiver inputs for 30µs, the on-board
power supply and drivers are shut off, reducing supply
current to 1µA. This occurs if the RS-232 cable is disconnected or the connected peripheral transmitters are
turned off. The system turns on again when a valid level
is applied to any RS-232 receiver input. As a result, the
system saves power without changes to the existing
BIOS or operating system. When using AutoShutdown,
the INVALID output is high when the device is on and
low when the device is shut down. Because INVALID
indicates the receiver inputs’ condition, it can be used
in any mode (Figure 3).
Table 2 and Figure 3c summarize the MAX3221/
MAX3223/MAX3243 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. Figures 3a, 3b, and 5a
depict valid and invalid RS-232 receiver levels.
A mouse or other system with AutoShutdown may need
time to wake up. Figure 4 shows a circuit that forces the
transmitters on for 100ms, allowing enough time for the
Table 1a. MAX3221/MAX3223
FFOORRCCEEOOFFFF
and
Enable Control Truth Table
Table 1b. MAX3243
FFOORRCCEEOOFFFF
Control
Truth Table
Active*11
Active*01
FFOORRCCEEOOFFFF
High-Z10
High-Z00
T_OUT
EENN
High-Z
Active
High-Z
Active
R_OUT
Active*1
High-Z0
T_OUT
FFOORRCCEEOOFFFF
Active*
High-Z
R_OUT
Active
Active
R2OUTB
Figure 3a. MAX32_ _ Entering 1µA Supply Mode via
AutoShutdown
*Note: If the part is in AutoShutdown mode (FORCEOFF = V
CC
,
FORCEON = GND), it is shut down if no valid RS-232
levels are present on all receiver inputs.
Figure 4. AutoShutdown with Initial Turn-On to Wake Up a
Mouse or Another System
Figure 3b. MAX32_ _ with Transmitters Enabled Using
AutoShutdown
Figure 3c. AutoShutdown Logic
+0.3V
R_IN
-0.3V
* TRANSMITTERS ARE DISABLED, REDUCING SUPPLY CURRENT TO 1µA IF
ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs.
+2.7V
R_IN
-2.7V
* TRANSMITTERS ARE ENABLED IF:
ANY RECEIVER INPUT IS GREATER THAN +2.7V OR LESS THAN -2.7V.
ANY RECEIVER INPUT HAS BEEN BETWEEN +0.3V AND -0.3V FOR LESS THAN 30µs.
FORCEOFF
FORCEON
INVALID
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.
POWER
MANAGEMENT
UNIT
MASTER SHDN LINE
FORCEOFF
30µs
COUNTER
R
30µs
COUNTER
R
0.1µF 1M
FORCEON
MAX3221
MAX3223
MAX3243
TO MAX32_ _
POWER SUPPLY
AND TRANSMITTERS
INVALID
TO MAX32_ _
POWER SUPPLY
INVALID
POWER DOWN
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
8 _______________________________________________________________________________________
other system to realize that the MAX3221/MAX3223/
MAX3243 is awake. If the other system outputs valid
RS-232 signals within that time, the RS-232 ports on
both systems remain enabled.
When shut down, the device’s charge pumps are turned
off, V+ decays to VCC, V- decays to ground, and the
transmitter outputs are disabled (high impedance). The
time required to exit shutdown is typically 100µs (Figure
5b).
Software-Controlled Shutdown
If direct software control is desired, INVALID can be
used to indicate DTR or Ring Indicator signal. Tie
FORCEOFF and FORCEON together to bypass AutoShutdown so the line acts like a SHDN input.
___________Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical for
proper operation; either polarized or nonpolarized
capacitors may be used. The charge pump requires
0.1µF capacitors for 3.3V operation. For other supply
voltages, refer to Table 3 for required capacitor values.
Do not use values smaller than those listed in Table 3.
Increasing the capacitor values (e.g., by a factor of 2)
reduces ripple on the transmitter outputs and slightly
reduces power consumption. C2, C3, and C4 can be
increased without changing C1’s value. However, do
not increase C1 without also increasing the values
of C2, C3, and C4 to maintain the proper ratios (C1
to the other capacitors).
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capacitors with a larger nominal value. The capacitor’s equivalent series resistance (ESR) usually rises at
low temperatures and influences the amount of ripple
on V+ and V-.
Table 2. AutoShutdown Logic
RS-232 SIGNAL
PRESENT AT
RECEIVER INPUT
FFOORRCCEEOOFFFF
INPUT
FORCEON
INPUT
IINNVVAALLIIDD
OUTPUT
TRANSCEIVER STATUS
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)
(b)
(a)
Figure 5. AutoShutdown Trip Levels
RECEIVER INPUT LEVELS
+2.7V
+0.3V
0V
-0.3V
-2.7V
TRANSMITTERS ENABLED, INVALID HIGH
INDETERMINATE
AUTOSHUTDOWN, TRANSMITTERS DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
INDETERMINATE
TRANSMITTERS ENABLED, INVALID HIGH
RECEIVER
INPUT
VOLTAGE
(V)
INVALID
OUTPUT
V
CC
(V)
0
t
INVL
V+
V
CC
0
V-
t
INVH
INVALID
REGION
t
WU
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
_______________________________________________________________________________________ 9
Power-Supply Decoupling
In most circumstances a 0.1µF bypass capacitor is
adequate. In applications that are sensitive to powersupply noise, decouple VCCto ground with a capacitor
of the same value as the charge-pump capacitor C1.
Connect bypass capacitors as close to the IC as possible.
Transmitter Outputs
when Exiting Shutdown
Figure 6 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two transmitter outputs are shown going to opposite RS-232
levels. Each transmitter is loaded with 3kΩ in parallel
with 2500pF. The transmitter outputs display no ringing
or undesirable transients as they come out of shutdown. Note that the transmitters are enabled only when
the magnitude of V- exceeds approximately 3V. Figure
7a shows the MAX3243’s transmitter output voltage
vs. current per transmitter. Figure 7b is a mouse driver
test circuit.
Mouse Driveability (MAX3243)
The MAX3243 has been specifically designed to power
serial mice while operating from low-voltage power supplies. It has been tested with samples of ten major mouse
models from six manufacturers including the leading
three: Logitech (5 models), Mouse Systems, and
Microsoft. The MAX3243 successfully drove all serial
mice and met their respective current and voltage
requirements. Figure 7a shows the transmitter outputs
under increasing load current. The MAX3243’s switching
regulator ensures the transmitters will supply at least ±5V
during worst-case conditions. The AutoShutdown feature
does not work with a mouse, so FORCEOFF and
FORCEON should be connected to V
CC
.
High Data Rates
The MAX3221/MAX3223/MAX3243 maintain the RS-232
±5.0V minimum transmitter output voltage even at high
data rates. Figure 8 shows a transmitter loopback test
circuit. Figure 9 shows a loopback test result at
120kbps, and Figure 10 shows the same test at
235kbps. For Figure 9, all three transmitters were driven simultaneously at 120kbps into RS-232 loads in parallel with 1000pF. For Figure 10, a single transmitter
was driven at 235kbps, but all three transmitters were
loaded with an RS-232 receiver in parallel with 1000pF.
Interconnection with 3V and 5V Logic
The MAX3221/MAX3223/MAX3243 can directly interface with various 5V logic families, including ACT and
HCT CMOS. See Table 4 for more information on possible combinations of interconnections.
Figure 7a. MAX3243 Transmitter Output Voltage vs. Load
Current per Transmitter
Figure 6. Transmitter Outputs when Exiting Shutdown or
Powering Up
5V/div
2V/div
50µs/div
= +3.3V
V
CC
C1–C4 = 0.1µF
T2
T1
6
5
OUT
OUT
V
OUT
+
-
V
OUT
4
VCC = 3.0V
3
2
1
0
-1
-2
-3
-4
TRANSMITTER OUTPUT VOLTAGE (V)
-5
-6
T
1
V
T
2
T
V
CC
01234567
LOAD CURRENT PER TRANSMITTER (mA)
V
3
MAX3222-04
+
-
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
10 ______________________________________________________________________________________
Figure 7b. Mouse Driver Test Circuit
+3.3V
26
V
CC
MAX3243
V+
V-
T1OUT 9
27
C3
0.1µF
3
C4
0.1µF
COMPUTER SERIAL PORT
+V
C1
0.1µF
C2
0.1µF
0.1µF
28
C1+
24
C1-
1
C2+
2
C2-
T1IN
14
LOGIC
INPUTS
LOGIC
OUTPUTS
T2IN
13
T3IN
12
R2OUTB
20
R1OUT
19
R2OUT
18
R3OUT
17
R4OUT
16
R5OUT
15
T2OUT 10
T3OUT
R1IN
5k
R2IN 5
5k
R3IN
5k
R4IN
5k
R5IN 8
11
4
6
7
RS-232
INPUTS
+V
-V
GND
Tx
SERIAL
MOUSE
V
CC
TO POWER
MANAGEMENT
UNIT
23
22
21
FORCEON
FORCEOFF
INVALID
GND
5k
25
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
______________________________________________________________________________________ 11
Figure 10. Loopback Test Result at 235kbps
Figure 8. Loopback Test Circuit
Figure 9. Loopback Test Result at 120kbps
Table 4. Logic Family Compatibility with
Various Supply Voltages
Table 3. Required Capacitor Values
VCCSUPPLY
VOLTAGE
(V)
COMPATIBILITY
3.3 3.3
Compatible with all CMOS
families.
5 5
Compatible with all TTL and
CMOS-logic families.
SYSTEM
POWERSUPPLY
VOLTAGE
(V)
5 3.3
Compatible with ACT and
HCT CMOS, and with TTL.
Incompatible with AC, HC,
or CD4000 CMOS.
V
CC
(V)
C1
(µF)
C2, C3, C4
(µF)
3.0 to 3.6 0.1 0.1
4.5 to 5.5 0.047 0.33
3.0 to 5.5 0.1 0.47
V
CC
0.1µF
V
MAX3221
MAX3223
MAX3243
GND
C1
C2
C1+
C1-
C2+
C2-
T_ IN
R_ OUT
0V
V
CC
EN (MAX3221/3)
FORCEOFF
CC
V+
C3
V-
C4
T_ OUT
R_ IN
5k
1000pF
T1IN
T1OUT
R1OUT
5µs/div
V
= +3.3V, 120kbps
CC
C1–C4 = 0.1µF
5V/div
5V/div
5V/div
T1IN
T1OUT
R1OUT
2µs/div
V
= +3.3V, 235kbps
CC
C1–C4 = 0.1µF
5V/div
5V/div
5V/div
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
12 ______________________________________________________________________________________
__________________________________________________Typical Operating Circuits
MAX3223
FORCEON
EN
14
1
R2OUT10
R1OUT15
FORCEOFF
20
INVALID 11
R2IN
9
GND
18
RS-232
OUTPUTS
TTL/CMOS
INPUTS
T2IN
12
T1IN
13
C2-
6
C2+
5
C1-
4
C1+
2
R1IN
16
T2OUT
8
T1OUT 17
V-
7
V+
3
V
CC
V
CC
C4
0.1µF
C3
0.1µF
0.1µF
19
C1
0.1µF
C2
0.1µF
C5
+3.3V
RS-232
INPUTS
TO POWER
MANAGEMENT
UNIT
TTL/CMOS
OUTPUTS
5k
5k
MAX3243
FORCEOFF
23
R5OUT
15
R4OUT
16
R3OUT
17
R2OUT
18
R1OUT
19
R2OUTB
20
LOGIC
OUTPUTS
5k
5k
5k
5k
5k
R5IN 8
R4IN
7
R3IN
6
R2IN 5
R1IN
4
RS-232
INPUTS
GND
25
RS-232
OUTPUTS
LOGIC
INPUTS
T3IN
12
T2IN
13
T1IN
14
C2-
2
C2+
1
C1-
24
C1+
28
T3OUT
11
T2OUT 10
T1OUT 9
V-
3
V+
27
V
CC
V
CC
C4
0.1µF
C3
0.1µF
0.1µF
26
C1
0.1µF
C2
0.1µF
FORCEON
INVALID
22
21
TO POWER
MANAGEMENT UNIT
+3.3V
+3.3V
15
V
CC
MAX3221
V+
V-
T1OUT 13
3
C3
0.1µF
7
C4
0.1µF
C1
0.1µF
C2
0.1µF
0.1µF
C5
2
C1+
4
C1-
5
C2+
6
C2-
11
T1IN
R1OUT9
1
12
EN
FORCEON
GND
14
R1IN 8
5k
INVALID 10
FORCEOFF
16
TO POWER
MANAGEMENT
UNIT
V
CC
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
______________________________________________________________________________________ 13
______3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim
0.1µF capacitors, MAX242 pinout23212022/23.0 to 5.5MAX3222
0.1µF capacitors, AutoShutdown23212022/23.0 to 5.5MAX3223
0.1µF capacitors, AutoShutdown
complementary receiver,
drives mice
23212013/53.0 to 5.5MAX3243
0.1µF capacitors, MAX232 pinout232120N/A2/23.0 to 5.5MAX3232
0.1µF capacitors, 16-pin SSOP23212011/13.0 to 5.5MAX3221
232
562
232
562
232
EIA/TIA-
232
OR 562
2.7 to 3.6
AutoShutdown, complementary
receiver, drives mice, transient
detection
23553/5MAX3212
0.1µF capacitors12022/23.0 to 3.6MAX563
Operates directly from batteries
without a voltage regulator
12022/21.8 to 4.25MAX218
No. OF
RECEIVERS
ACTIVE IN
SHUTDOWN
POWER-
SUPPLY
VOLTAGE
(V)
230kbps guaranteed data rate23053/52.7 to 5.25MAX562
Drives mice12053/53.0 to 3.6MAX212
FEATURES
GUAR-
ANTEED
DATA
RATE
(kbps)
No. OF
TRANSMITTERS/
RECEIVERS
PART
0.1µF capacitors, 2 complementary receivers, drives mice
23212053/53.0 to 5.5MAX3241
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
14 ______________________________________________________________________________________
__________________________________________________________Pin Configurations
TOP VIEW
___________________Chip Information
MAX3221
TRANSISTOR COUNT: 269
MAX3223
TRANSISTOR COUNT: 339
MAX3243
TRANSISTOR COUNT: 476
16
15
14
13
12
11
10
9
FORCEOFF
V
CC
GND
T1OUT
FORCEON
T1IN
INVALID
R1OUT
C1+
C1-
C2+
C2-
R1IN
EN
1
2
3
V+
4
MAX3221
5
6
7
V-
8
SSOP/TSSOP
C2+
1
C2-
2
V-
3
R1IN
4
R2IN
5
R3IN
R4IN
R5IN
T1OUT
T2OUT
T3OUT
T3IN
T2IN
T1IN
MAX3243
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
C1+
V+
V
CC
GND
C1-
FORCEON
FORCEOFF
INVALID
R2OUTB
R1OUT
R2OUT
R3OUT
R4OUT
R5OUT
EN
1
C1+
2
V+
3
C1-
4
C2+
5
C2-
6
V-
7
T2OUT
8
R2IN
9
R2OUT
10
DIP/SSOP/TSSOP
MAX3223
20
19
18
17
16
15
14
13
12
11
FORCEOFF
V
CC
GND
T1OUT
R1IN
R1OUT
FORCEON
T1IN
T2IN
INVALID
SO/SSOP/TSSOP
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
______________________________________________________________________________________ 15
________________________________________________________Package Information
SSOP.EPS
TSSOP.EPS
MAX3221/MAX3223/MAX3243
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown
___________________________________________Package Information (continued)
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
SOICW.EPS
PDIPN.EPS
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