Maxim MAX324 ±15kv esd-protected, 1ua, 3.0v to 5.5v, 250kbps, rs-232 transceivers with autoshutdown Datasheet

19-1283; Rev 2; 1/98
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
The MAX3221E/MAX3223E/MAX3243E are 3V-powered
EIA/TIA-232 and V.28/V.24 communications interfaces
with automatic shutdown/wakeup features, high datarate capabilities, and enhanced electrostatic discharge
(ESD) protection. All transmitter outputs and receiver
inputs are protected to ±15kV using IEC 1000-4-2 AirGap Discharge, to ±8kV using IEC 1000-4-2 Contact
Discharge, and to ±15kV using the Human Body Model.
The MAX3221E/MAX3223E/MAX3243E achieve a
1µA supply current with Maxim’s revolutionary
AutoShutdown™ feature. They save power without
changes to the existing BIOS or operating system by entering low-power shutdown mode when the RS-232 cable is
disconnected, or when the transmitters of the connected
peripherals are off.
The transceivers have a proprietary low-dropout transmitter output stage, delivering true RS-232 performance
from a +3.0V to +5.5V supply with a dual charge pump.
The charge pump requires only four small 0.1µF capacitors for operation from a +3.3V supply. Each device is
guaranteed to run at data rates of 250kbps while maintaining RS-232 output levels.
The MAX3221E contains just one driver and one receiver,
making it the smallest single-supply RS-232 transceiver.
The MAX3223E has two drivers and two receivers. The
MAX3243E is a complete 3-driver/5-receiver serial port
ideal for notebook or subnotebook computers. It also
includes two noninverting receiver outputs that are always
active, allowing external devices to be monitored without
forward biasing the protection diodes in circuitry that may
be powered down.
The MAX3221E, MAX3223E, and MAX3243E are available in space-saving SSOP packages.
Features
♦ ESD Protection for RS-232 I/O Pins:
±15kV—Human Body Model
±8kV—IEC1000-4-2, Contact Discharge
±15kV—IEC1000-4-2, Air-Gap Discharge
♦ Latchup Free
♦ 1µA Supply Current
♦ 250kbps Guaranteed Data Rate
♦ 6V/µs Guaranteed Slew Rate
♦ Meets EIA/TIA-232 Specifications Down to 3.0V
♦ Smallest Single-Supply RS-232 Transceiver
(MAX3221E)
♦ Guaranteed Mouse Driveability (MAX3243E)
♦ Small 0.1µF Capacitors
Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX3221ECAE
0°C to +70°C
16 SSOP
MAX3221EEAE
-40°C to +85°C
16 SSOP
MAX3223ECPP
0°C to +70°C
20 Plastic DIP
MAX3223ECAP
0°C to +70°C
20 SSOP
MAX3223EEPP
-40°C to +85°C
20 Plastic DIP
MAX3223EEAP
-40°C to +85°C
20 SSOP
MAX3243ECWI
0°C to +70°C
28 Wide SO
MAX3243ECAI
0°C to +70°C
28 SSOP
MAX3243EEWI
-40°C to +85°C
28 Wide SO
MAX3243EEAI
-40°C to +85°C
28 SSOP
Applications
Selector Guide
Notebook, Subnotebook, and Palmtop Computers
Cellular Phones
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
Printers
PART
NO. OF
VCC RANGE
DRIVERS/
(V)
RECEIVERS
AUTOSHUTDOWN
MAX3221E
1/1
3.0 to 5.5
✔
MAX3223E
2/2
3.0 to 5.5
✔
MAX3243E
3/5
3.0 to 5.5
✔
Pin Configurations appear at end of data sheet.
Typical Operating Circuits appear at end of data sheet.
AutoShutdown is a trademark of Maxim Integrated Products.
†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; 5,649,210; and other patents pending.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAX3221E/MAX3223E/MAX3243E †
General Description
MAX3221E/MAX3223E/MAX3243E
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +6V
V+ to GND (Note 1) ..................................................-0.3V to +7V
V- to GND (Note 1) ...................................................+0.3V to -7V
V+ + |V-| (Note 1) .................................................................+13V
Input Voltages
T_IN, EN, FORCEON, FORCEOFF to GND ............-0.3V to +6V
R_IN to GND ......................................................................±25V
Output Voltages
T_OUT to GND................................................................±13.2V
R_OUT, R2OUTB, INVALID to GND .........-0.3V to (VCC + 0.3V)
Short-Circuit Duration
T_OUT to GND .........................................................Continuous
Continuous Power Dissipation (TA = +70°C)
16-Pin SSOP (derate 7.14mW/°C above +70°C) ...........571mW
20-Pin Plastic DIP (derate 11.11mW/°C above +70°C)....889mW
20-Pin SSOP (derate 8.00mW/°C above +70°C) ...........640mW
28-Pin Wide SO (derate 12.50mW/°C above +70°C)............1W
28-Pin SSOP (derate 9.52mW/°C above +70°C)............762mW
Operating Temperature Ranges
MAX32_ _EC_ _ ....................................................0°C to +70°C
MAX32_ _EE_ _..................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°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.
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
(VCC = +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC CHARACTERISTICS (VCC = 3.3V or 5.0V, TA = +25°C)
Supply Current, AutoShutdown
FORCEON = GND,
FORCEOFF = VCC, all R_IN open
1.0
10
µA
Supply Current, Shutdown
FORCEOFF = GND
1.0
10
µA
Supply Current,
AutoShutdown Disabled
FORCEON = FORCEOFF = VCC,
no load
0.3
1
mA
0.8
V
LOGIC INPUTS
Input Logic Threshold Low
T_IN, EN, FORCEON, FORCEOFF
Input Logic Threshold High
T_IN, EN, FORCEON,
FORCEOFF
VCC = 3.3V
2.0
VCC = 5.0V
2.4
Transmitter Input Hysteresis
V
0.5
V
T_IN, EN, FORCEON, FORCEOFF
±0.01
±1
µA
Output Leakage Current
R_OUT receivers disabled
±0.05
±10
µA
Output Voltage Low
IOUT = 1.6mA
0.4
V
Output Voltage High
IOUT = -1.0mA
Input Leakage Current
RECEIVER OUTPUTS
VCC - 0.6
VCC - 0.1
V
AUTOSHUTDOWN (FORCEON = GND, FORCEOFF = VCC)
2
Receiver Input Threshold to
INVALID Output High
Figure 5a
Receiver Input Threshold to
INVALID Output Low
Figure 5a
INVALID Output Voltage Low
IOUT = 1.6mA
INVALID Output Voltage High
IOUT = -1.0mA
Positive threshold
Negative threshold
2.7
-2.7
-0.3
VCC - 0.6
_______________________________________________________________________________________
V
0.3
V
0.4
V
V
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
(VCC = +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Receiver Positive or Negative
Threshold to INVALID High
tINVH
VCC = 5V, Figure 5b
1
µs
Receiver Positive or Negative
Threshold to INVALID Low
tINVL
VCC = 5V, Figure 5b
30
µs
Receiver or Transmitter Edge to
Transmitters Enabled
tWU
VCC = 5V, Figure 5b
100
µs
RECEIVER
INPUTS
Input Voltage
Range
-25
25
V
Input Voltage Range
-25
25
V
Input Threshold Low
TA = +25°C
Input Threshold High
TA = +25°C
VCC = 3.3V
0.6
1.2
VCC = 5.0V
0.8
1.5
V
VCC = 3.3V
1.5
2.4
VCC = 5.0V
1.8
2.4
Input Hysteresis
0.5
Input Resistance
3
5
V
V
7
kΩ
TRANSMITTER OUTPUTS
Output Voltage Swing
All transmitter outputs loaded with
3kΩ to ground
±5
±5.4
Output Resistance
VCC = V+ = V- = 0, TOUT = ±2V
300
10M
Output Short-Circuit Current
Output Leakage Current
VOUT = ±12V, VCC = 0 or 3V to
5.5V, transmitters disabled
V
Ω
±60
mA
±25
µA
MOUSE DRIVEABILITY (MAX3243E)
Transmitter Output Voltage
T1IN = T2IN = GND, T3IN = VCC,
T3OUT loaded with 3kΩ to GND,
T1OUT and T2OUT loaded with
2.5mA each
±5.0
V
ESD PROTECTION
R_IN, T_OUT
IEC 1000-4-2 Air-Gap Discharge
±15
IEC 1000-4-2 Contact Discharge
±8
Human Body Model
±15
kV
kV
_______________________________________________________________________________________
3
MAX3221E/MAX3223E/MAX3243E
ELECTRICAL CHARACTERISTICS (continued)
TIMING CHARACTERISTICS—MAX3221E/MAX3223E/MAX3243E
(VCC = +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
Maximum Data Rate
tPHL
Receiver Propagation Delay
CONDITIONS
MIN
RL = 3kΩ, CL = 1000pF,
one transmitter switching
250
TYP
UNITS
kbps
0.15
CL = 150pF
tPLH
MAX
µs
0.15
Receiver Output Enable Time
Normal operation
200
ns
Receiver Output Disable Time
Normal operation
200
ns
(Note 3)
100
ns
50
ns
Transmitter Skew
 tPHL - tPLH 
Receiver Skew
 tPHL - tPLH 
VCC = 3.3V,
RL = 3kΩ to 7kΩ,
TA = +25°C,
measured from
+3V to -3V or
-3V to +3V
Transition-Region Slew Rate
CL = 150pF to
1000pF
6
30
V/µs
CL = 150pF to
2500pF
4
30
Note 2: C1–C4 = 0.1µF, tested at 3.3V ±10%. C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%.
Note 3: Transmitter skew is measured at the transmitter zero cross points.
Typical Operating Characteristics
(VCC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ and CL, TA = +25°C, unless otherwise noted.)
MAX3221E/MAX3223E
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
VOUT+
4
3
2
14
1
0
-1
-2
-3
-4
-5
-6
SLEW RATE (V/µs)
12
T1 TRANSMITTING AT 250kbps
T2 (MAX3223E) TRANSMITTING AT 15.6kbps
-SLEW
10
+SLEW
8
6
4
2
VOUT-
FOR DATA RATES UP TO 250kbps
0
0
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
4
16
MAX3221-TOC2
6
5
MAX3221E/MAX3223E
SLEW RATE vs. LOAD CAPACITANCE
MAX3221E-01
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3221E/MAX3223E/MAX3243E
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
5000
0
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
_______________________________________________________________________________________
5000
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
250kbps
35
30
120kbps
25
20
20kbps
15
10
T1 TRANSMITTING AT 250kbps
T2 (MAX3223E) TRANSMITTING AT 15.6kbps
5
6
5
1 TRANSMITTER AT 250kbps
2 TRANSMITTERS AT 15.6kbps
2
1
0
-1
-2
-3
-4
VOUT-
-5
-6
0
0
1000
2000
3000
4000
0
5000
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
MAX3243E
SLEW RATE vs. LOAD CAPACITANCE
MAX3243E
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
50
SUPPLY CURRENT (mA)
12
10
8
6
4
250kbps
40
120kbps
30
20kbps
20
10
2
0
5000
60
MAX3243E-05
14
SLEW RATE (V/µs)
VOUT+
4
3
MAX3243E-06
SUPPLY CURRENT (mA)
40
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3224E-03
45
MAX3224E-04
MAX3243E
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3221E/MAX3223E
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
T1 TRANSMITTING AT 250kbps
T2 (MAX3223E) TRANSMITTING AT 15.6kbps
0
0
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
_______________________________________________________________________________________
5
MAX3221E/MAX3223E/MAX3243E
Typical Operating Characteristics (continued)
(VCC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ and CL, TA = +25°C, unless otherwise noted.)
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
MAX3221E/MAX3223E/MAX3243E
Pin Description
PIN
NAME
FUNCTION
—
EN
Receiver Enable Control. Drive low for normal operation. Drive high to
force the receiver outputs (R_OUT) into a high-impedance state.
2
28
C1+
3
3
27
V+
+5.5V generated by the charge pump
4
4
24
C1-
Negative terminal of the voltage doubler Charge-Pump Capacitor
5
5
1
C2+
Positive terminal of inverting Charge-Pump Capacitor
6
6
2
C2-
Negative terminal of inverting Charge-Pump Capacitor
7
7
3
V-
8
9, 16
4–8
R_IN
9
10, 15
15–19
R_OUT
10
11
21
INVALID
11
12, 13
12, 13, 14
T_IN
12
14
23
FORCEON
13
8, 17
9, 10, 11
T_OUT
—
—
20
R2OUTB
14
18
25
GND
Ground
15
19
26
VCC
+3.0V to +5.5V Supply Voltage
16
20
22
FORCEOFF
MAX3221E
MAX3223E
MAX3243E
1
1
2
Positive terminal of the voltage doubler Charge-Pump Capacitor
-5.5V generated by the charge pump
RS-232 Receiver Inputs
TTL/CMOS Receiver Outputs
Output of the Valid Signal Detector. INVALID is enabled high if a valid
RS-232 level is present on any receiver input.
TTL/CMOS Transmitter Inputs
Drive high to override automatic circuitry keeping transmitters and
charge pump on (FORCEOFF must be high) (Table 1).
RS-232 Transmitter Outputs
TTL/CMOS Noninverting Complementary Receiver Output. Always
active.
Force-Off Input, active low. Drive low to shut down transmitters,
receivers (MAX3243E, except R2OUTB), and on-board charge pump.
This overrides all automatic circuitry and FORCEON (Table 1).
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3221E/MAX3223E/MAX3243E’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), over the
+3.0V to +5.5V VCC range. The charge pumps operate
in 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.
LapLink is a trademark of Traveling Software.
6
RS-232 Transmitters
The transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. They
guarantee a 250kbps data rate with worst-case loads
of 3kΩ in parallel with 1000pF, providing compatibility
with PC-to-PC communication software such as
LapLink™. Transmitters can be paralleled to drive multiple receivers. The MAX3243E has been specifically
designed to drive serial mice. Figure 1 shows a complete system connection.
When FORCEOFF is driven to ground, or the
AutoShutdown circuitry senses invalid voltage levels on
all receiver inputs, the transmitters are disabled and the
outputs are forced into a high-impedance state. When
powered off or shut down, the output can be driven up
to ±12V. The transmitter inputs do not have pull-up
resistors.
_______________________________________________________________________________________
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
MAX3221E/MAX3223E/MAX3243E
POWERMANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
VCC
FORCEOFF
FORCEON
INVALID
PROTECTION
DIODE
MAX3243E
PREVIOUS
RS-232
VCC
I
Rx
5k
UART
Tx
CPU
I/O
CHIP
WITH
UART
GND
SHDN = GND
RS-232
a)
OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
VCC
TO
LOGIC
µP TRANSITION
DETECTOR
Figure 1. Interface Under Control of PMU
I
PROTECTION
DIODE
RS-232 Receivers
The MAX3221E/MAX3223E/MAX3243E’s receivers convert RS-232 signals to CMOS-logic output levels. All
receivers have inverting three-state outputs and can be
active or inactive. In shutdown (FORCEOFF = low) or in
AutoShutdown, the MAX3221E/MAX3223E’s receivers
are active (Table 1). Drive EN high to place the receiver(s) in a high-impedance state. The MAX3243E’s
receivers are high-impedance when the part is in shutdown (FORCEOFF = low).
The MAX3243E features an extra, always-active complementary output (R2OUTB). R2OUTB monitors
receiver activity while the other receivers are highimpedance. This allows Ring Indicator to be monitored
without forward biasing other devices connected to the
receiver outputs. This is ideal for systems where VCC
drops to 0 in shutdown to accommodate peripherals
such as UARTs (Figure 2).
MAX3243E
R2OUTB
VCC
Rx
THREE-STATED
UART
5k
Tx
GND
b)
R2IN
R2OUT
T1IN
T1OUT
FORCEOFF = GND
NEW MAX3243E: IN SHUTDOWN, R2OUTB IS USED TO MONITOR EXTERNAL
DEVICES AND R2OUT IS THREE STATED, ELIMINATING A CURRENT PATH
THROUGH THE UART'S PROTECTION DIODE.
Figure 2. The MAX3243E detects RS-232 activity when the
UART and interface are shut down.
_______________________________________________________________________________________
7
MAX3221E/MAX3223E/MAX3243E
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
Table 1. Output Control Truth Table
FORCEON
FORCEOFF
EN
(MAX3221E/
MAX3223E)
VALID
RECEIVER
LEVEL
T_OUT
R_OUT
(MAX3221E/
MAX3223E)
R_OUT
(MAX3243E)
R2OUTB
(MAX3243E)
Shutdown
(Forced Off)
X
0
0
X
High-Z
Active
High-Z
Active
X
0
1
X
High-Z
High-Z
High-Z
Active
Normal Operation
(Forced On)
1
1
0
X
Active
Active
Active
Active
1
1
1
X
Active
High-Z
Active
Active
Normal Operation
(AutoShutdown)
0
1
0
Yes
Active
Active
Active
Active
0
1
1
Yes
Active
High-Z
Active
Active
Shutdown
(AutoShutdown)
0
1
0
No
High-Z
Active
High-Z
Active
0
1
1
No
High-Z
High-Z
High-Z
Active
OPERATION
STATUS
X = Don’t Care
+2.7V
+0.3V
R_IN
-0.3V
30µs
COUNTER
R
TO MAX32_ _E
POWER SUPPLY
AND TRANSMITTERS
R_IN
INVALID
* 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
30µs
COUNTER
R
TO MAX32_ _E
POWER SUPPLY
INVALID
* 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.
Figure 3a. MAX32_ _E Entering 1µA Supply Mode via
AutoShutdown
Figure 3b. MAX32__E with Transmitters Enabled Using
AutoShutdown
The MAX3221E/MAX3223E/MAX3243E feature an
INVALID output that is enabled low when no valid RS-232
signal levels have been detected on all receiver inputs.
INVALID is functional in any mode (Figures 3 and 5).
signal levels on all receiver inputs for 30µs, the onboard charge pump 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 device 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.
AutoShutdown
The MAX3221E/MAX3223E/MAX3243E achieve a 1µA
supply current with Maxim’s new AutoShutdown feature, which operates when FORCEON is low and
FORCEOFF is high. When these devices sense no valid
8
_______________________________________________________________________________________
1µA Supply-Current, True +3V to +5.5V
RS-232 Transceivers with AutoShutdown™
POWER DOWN
FORCEON
INVALID
Table 2. INVALID Truth Table
RS-232 SIGNAL PRESENT
AT ANY RECEIVER INPUT
INVALID OUTPUT
Yes
High
No
Low
INVALID IS AN INTERNALLY GENERATED SIGNAL
THAT IS USED BY THE AUTOSHUTDOWN LOGIC
AND APPEARS AS AN OUTPUT OF THE DEVICE.
MAX3221E/MAX3223E/MAX3243E
FORCEOFF
POWER DOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3c. MAX32_ _E AutoShutdown Logic
TRANSMITTERS ENABLED, INVALID HIGH
MASTER SHDN LINE
0.1µF
1M
FORCEOFF FORCEON
MAX3221E
MAX3223E
MAX3243E
+2.7V
RECEIVER INPUT LEVELS
POWERMANAGEMENT
UNIT
INDETERMINATE
+0.3V
0
AUTOSHUTDOWN, TRANSMITTERS DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
-0.3V
INDETERMINATE
-2.7V
TRANSMITTERS ENABLED, INVALID HIGH
Figure 4. AutoShutdown with Initial Turn-On to Wake Up a
Mouse or Another System
Table 2 and Figure 3c summarize the MAX3221E/
MAX3223E/MAX3243E operating modes. FORCEON
and FORCEOFF override AutoShutdown. 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. Figure 5 shows the input levels and timing diagram for AutoShutdown operation.
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
other system to realize that the MAX3221E/MAX3223E/
MAX3243E are awake. If the other system transmits
valid RS-232 signals within that time, the RS-232 ports
on both systems remain enabled.
a)
RECEIVER
INPUT
VOLTAGE
(V)
VCC
INVALID
OUTPUT
(V)
0
Software-Controlled Shutdown
tINVL
tINVH
tWU
V+
VCC
0
When shut down, the device’s charge pumps are off, V+
is pulled to VCC, V- is pulled to ground, and the transmitter outputs are high impedance. The time required to
exit shutdown is typically 100µs (Figure 5b).
If direct software control is desired, INVALID can be
used to indicate DTR or Ring Indicator signal. Connect
FORCEOFF and FORCEON together to disable AutoShutdown so the line acts like a SHDN input.
INVALID
REGION
V-
b)
Figure 5. AutoShutdown Trip Levels
_______________________________________________________________________________________
9
RC 1M
CHARGE-CURRENT
LIMIT RESISTOR
HIGHVOLTAGE
DC
SOURCE
Cs
100pF
RC 50M to 100M
RD 1500Ω
CHARGE CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
DEVICE
UNDER
TEST
STORAGE
CAPACITOR
HIGHVOLTAGE
DC
SOURCE
Cs
150pF
RD 330Ω
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 7a. IEC1000-4-2 ESD Test Model
Figure 6a. Human Body ESD Test Models
I
IP 100%
90%
Ir
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
100%
90%
AMPERES
I PEAK
MAX3221E/MAX3223E/MAX3243E
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
36.8%
10%
0
0
tRL
TIME
tDL
CURRENT WAVEFORM
Figure 6b. Human Body Model Current Waveform
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures are
incorporated on all pins to protect against electrostatic
discharges encountered during handling and assembly.
The driver outputs and receiver inputs of the
MAX3221E/MAX3223E/MAX3243E have extra protection
against static electricity. Maxim’s engineers have developed state-of-the-art structures to protect these pins
against ESD of ±15kV without damage. The ESD structures withstand high ESD in all states: normal operation,
shutdown, and powered down. After an ESD event,
Maxim’s E versions keep working without latchup, whereas competing RS-232 products can latch and must be
powered down to remove latchup.
ESD protection can be tested in various ways; the transmitter outputs and receiver inputs of this product family
are characterized for protection to the following limits:
1) ±15kV using the Human Body Model
2) ±8kV using the contact-discharge method specified in
IEC1000-4-2
3) ±15kV using IEC1000-4-2’s air-gap method
10
10%
t r = 0.7ns to 1ns
t
30ns
60ns
Figure 7b. IEC1000-4-2 ESD Generator Current Waveform
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents
test setup, test methodology, and test results.
Human Body Model
Figure 6a shows the Human Body Model, and Figure
6b shows the current waveform it generates when discharged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device
through a 1.5kΩ resistor.
IEC1000-4-2
The IEC1000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The MAX3221E/
MAX3223E/MAX3243E help you design equipment that
meets Level 4 (the highest level) of IEC1000-4-2, without the need for additional ESD-protection components.
______________________________________________________________________________________
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
Table 3. Required Capacitor Values
The air-gap test involves approaching the device with a
charged probe. The contact-discharge method connects
the probe to the device before the probe is energized.
Table 4. Logic Family Compatibility with
Various Supply Voltages
Machine Model
The Machine Model for ESD tests all pins using a 200pF
storage capacitor and zero discharge resistance. Its
objective is to emulate the stress caused by contact that
occurs with handling and assembly during manufacturing. Of course, all pins require this protection during
manufacturing, not just RS-232 inputs and outputs.
Therefore, after PC board assembly, the Machine Model
is less relevant to I/O ports.
___________Applications Information
VCC
(V)
C1, CBYPASS
(µF)
C2, C3, C4
(µF)
0.22
3.0 to 3.6
0.22
3.15 to 3.6
0.1
0.1
4.5 to 5.5
0.047
0.33
3.0 to 5.5
0.22
1
SYSTEM
POWERSUPPLY
VOLTAGE
(V)
VCC SUPPLY
VOLTAGE
(V)
COMPATIBILITY
3.3
3.3
Compatible with all CMOS
families.
5
5
5
3.3
Compatible with all TTL and
CMOS-logic families.
Compatible with ACT and
HCT CMOS, and with TTL.
Incompatible with AC, HC,
or CD4000 CMOS.
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-.
Power-Supply Decoupling
In most circumstances, a 0.1µF VCC bypass capacitor is
adequate. In applications that are sensitive to powersupply noise, use a capacitor of the same value as the
charge-pump capacitor C1. Connect bypass capacitors
as close to the IC as possible.
FORCEON =
FORCEOFF
T2OUT
5V/div
2V/div
T1OUT
VCC = 3.3V
C1–C4 = 0.1µF
40µs/div
Figure 8. Transmitter Outputs Exiting Shutdown or Powering Up
Transmitter Outputs
when Exiting Shutdown
Figure 8 shows two transmitter outputs when exiting
shut down mode. As they become active, the two transmitter outputs are shown going to opposite RS-232 levels (one transmitter output is high, the other is low).
Each transmitter is loaded with 3kΩ in parallel with
1000pF. The transmitter outputs display no ringing or
undesirable transients as they come out of shutdown,
and are enabled only when the magnitude of Vexceeds approximately -3V.
______________________________________________________________________________________
11
MAX3221E/MAX3223E/MAX3243E
The major difference between tests done using the
Human Body Model and IEC1000-4-2 is higher peak
current in IEC1000-4-2, because series resistance is
lower in the IEC1000-4-2 model. Hence, the ESD withstand voltage measured to IEC1000-4-2 is generally
lower than that measured using the Human Body
Model. Figure 7a shows the IEEE1000-4-2 model and
Figure 7b shows the current waveform for the ±8kV
IEC1000-4-2 Level 4 ESD contact-discharge test.
High Data Rates
The MAX3221E/MAX3223E/MAX3243E maintain the RS232 ±5.0V minimum transmitter output voltage even at
high data rates. Figure 9 shows a transmitter loopback
test circuit. Figure 10 shows a loopback test result at
120kbps, and Figure 11 shows the same test at 250kbps.
For Figure 10, all three transmitters were driven simultaneously at 120kbps into RS-232 loads in parallel with
1000pF. For Figure 11, a single transmitter was driven at
250kbps, and all three transmitters were loaded with an
RS-232 receiver in parallel with 1000pF.
VCC
0.1µF
VCC
C1+
V+
C3
C1
C1C2+
C2
C2-
MAX3221E
MAX3223E
MAX3243E
V-
T1IN
5V/div
T1OUT
5V/div
C4
T_ OUT
T_ IN
R_ IN
R_ OUT
0V
Mouse Driveability (MAX3243E)
The MAX3243E has been specifically designed to power
serial mice while operating from low-voltage power supplies. It has been tested with leading mouse brands such
as Logitech and Microsoft. When tested, the MAX3243E
successfully drove all serial mice and met their respective
current and voltage requirements. The MAX3243E’s regulated dual charge pump ensures the transmitters will supply at least ±5V during worst-case conditions. Figure 12a
shows the transmitter outputs under increasing load current. The AutoShutdown feature does not work with a
mouse, so FORCEOFF and FORCEON should be connected to VCC. Figure 12b (on the following page) shows
a mouse driver test circuit. To achieve mouse driveability
with 1µA supply current when the port is inactive, use
parts with the AutoShutdown Plus feature (such as the
MAX3244E and MAX3245E).
EN (MAX3221/3E)
5k
5V/div
R1OUT
VCC = 3.3V
1000pF
VCC
FORCEOFF
GND
2µs/div
Figure 11. Loopback Test Result at 250kbps
5V/div
T1IN
5V/div
T1OUT
5V/div
R1OUT
VCC = 3.3V
6
5
4
VOUT+
VCC = 3.0V
3
2
1
MAX2343E-FIG15
Figure 9. Loopback Test Circuit
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3221E/MAX3223E/MAX3243E
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
VOUT+
0
-1
-2
VCC
-3
-4
-5
-6
VOUTVOUT-
0
1
2
3
4
5
6
7
8
9
10
LOAD CURRENT PER TRANSMITTER (mA)
2µs/div
Figure 10. Loopback Test Result at 120kbps
12
Figure 12a. Transmitter Output Voltage vs. Load Current per
Transmitter
______________________________________________________________________________________
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
MAX3221E/MAX3223E/MAX3243E
+3.3V
26
0.1µF
28
C1
0.1µF
24
1
C2
0.1µF
2
LOGIC
INPUTS
VCC
27
C1+
V+
C3
0.1µF
C1C2+
COMPUTER SERIAL PORT
3
MAX3243E
V-
C4
0.1µF
C2-
14
T1IN
T1OUT
9
+V
13
T2IN
T2OUT
10
+V
12
T3IN
T3OUT
11
-V
20
R2OUTB
19
R1OUT
GND
R1IN
4
R2IN
5
R3IN
6
R4IN
7
R5IN
8
Tx
5k
18
R2OUT
LOGIC
OUTPUTS
5k
17
R3OUT
RS-232
INPUTS
5k
16
R4OUT
5k
15
VCC
VCC
TO POWERMANAGEMENT
UNIT
23
22
21
R5OUT
SERIAL
MOUSE
5k
FORCEON
FORCEOFF
INVALID
GND
25
Figure 12b. Mouse Driver Test Circuit
______________________________________________________________________________________
13
MAX3221E/MAX3223E/MAX3243E
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
Interconnection with 3V and 5V Logic
HCT CMOS. See Table 4 for more information on possible combinations of interconnections.
The MAX3221E/MAX3223E/MAX3243E can directly interface with various 5V logic families, including ACT and
Table 5. ±15kV ESD-Protected, 3.0V to 5.5V Powered RS-232 Transceivers from Maxim
PART
Supply
Voltage
Range
(V)
No.
of
Tx/Rx
Human
Body
Model
(kV)
IEC 1000-4-2
Contact
Discharge
(kV)
IEC 1000-4-2
Air-Gap
Discharge
(kV)
Guaranteed
Data Rate
(kbps)
MAX3241E
+3.0 to +5.5
3/5
300
—
MAX3243E
+3.0 to +5.5
3/5
1
—
—
±15
±8
±15
250
Yes
±15
±8
±15
MAX3244E
+3.0 to +5.5
3/5
1
Yes
250
—
±15
±8
±15
MAX3245E
+3.0 to +5.5
3/5
1
250
Yes
—
±15
±8
±15
1Mbps
MAX3232E
+3.0 to +5.5
2/2
300
—
—
±15
±8
±15
250
MAX3222E
+3.0 to +5.5
MAX3223E
+3.0 to +5.5
2/2
300
—
—
±15
±8
±15
250
2/2
1
—
Yes
±15
±8
±15
MAX3224E
250
+3.0 to +5.5
2/2
1
Yes
—
±15
±8
±15
250
MAX3225E
+3.0 to +5.5
2/2
1
Yes
—
±15
±8
±15
1Mbps
MAX3221E
+3.0 to +5.5
1/1
1
—
Yes
±15
±8
±15
250
MAX3226E
+3.0 to +5.5
1/1
1
Yes
—
±15
±8
±15
250
MAX3227E
+3.0 to +5.5
1/1
1
Yes
—
±15
±8
±15
1Mbps
Supply
AutoAutoCurrent Shutdown Shutdown
(µA)
Plus
___________________Chip Information
MAX3221E
TRANSISTOR COUNT: 269
MAX3223E
TRANSISTOR COUNT: 339
MAX3243E
TRANSISTOR COUNT: 476
14
______________________________________________________________________________________
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
+3.3V
15
0.1µF
CBYPASS
2 C1+
C1
0.1µF
4 C15
C2
0.1µF
6
VCC
3
V+
C3
0.1µF
MAX3221E
C2+
7
V-
C4
0.1µF
C2-
11 T1IN
+3.3V
CBYPASS
28 C1+
C1
0.1µF
T1OUT 13
24
1
C2
0.1µF
R1IN 8
9 R1OUT
2
5k
12
TO POWERMANAGEMENT
UNIT
INVALID 10
1 EN
FORCEOFF 16
FORCEON
GND
LOGIC
INPUTS
MAX3243E
V-
2 C1+
4
6
C1-
MAX3223E
C2+
V-
C3
0.1µF
7
14 T1IN
T1OUT 9
13 T2IN
T2OUT 10
12 T3IN
T3OUT 11
R1IN 4
R2IN
17 R3OUT
R3IN 6
5k
15 R5OUT
23
R1IN 16
R2IN
RS-232
INPUTS
INVALID 11
1 EN
FORCEOFF 20
FORCEON
GND
VCC
9
TO POWERMANAGEMENT UNIT
5k
RS-232
INPUTS
R4IN 7
RS-232
OUTPUTS
5k
5
5k
16 R4OUT
T2OUT 8
10 R2OUT
RS-232
OUTPUTS
5k
T1OUT 17
TTL/CMOS
OUTPUTS
14
LOGIC
OUTPUTS
C4
0.1µF
C2-
15 R1OUT
C4
0.1µF
C2-
18 R2OUT
3
V+
12 T2IN
3
5k
VCC
13 T1IN
TTL/CMOS
INPUTS
C2+
19
0.1µF
C3
0.1µF
C1-
19 R1OUT
5
C2
0.1µF
27
V+
20 R2OUTB
+3.3V
C1
0.1µF
VCC
VCC
14
CBYPASS
26
0.1µF
22
R5IN 8
5k
FORCEON
FORCEOFF
21 INVALID
GND
25
TO POWERMANAGEMENT
UNIT
VCC
18
______________________________________________________________________________________
15
MAX3221E/MAX3223E/MAX3243E
Typical Operating Circuits
MAX3221E/MAX3223E/MAX3243E
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
Pin Configurations
TOP VIEW
EN 1
EN 1
V+ 3
C1- 4
19 VCC
15 VCC
V+ 3
18 GND
14 GND
C1- 4
13 T1OUT
C2+ 5
12 FORCEON
C2- 6
16 FORCEOFF
C1+ 2
MAX3221E
C2+ 5
C2- 6
V- 7
17 T1OUT
MAX3223E
10 INVALID
16 R1IN
15 R1OUT
V- 7
11 T1IN
14 FORCEON
T2OUT 8
13 T1IN
R2IN 9
12 T2IN
9 R1OUT
R1IN 8
20 FORCEOFF
C1+ 2
R2OUT 10
11 INVALID
SSOP
DIP/SSOP
C2+ 1
28 C1+
C2- 2
27 V+
V- 3
26 VCC
R1IN 4
25 GND
R2IN 5
R3IN 6
MAX3243E
24 C123 FORCEON
R4IN 7
22 FORCEOFF
R5IN 8
21 INVALID
T1OUT 9
20 R2OUTB
T2OUT 10
19 R1OUT
T3OUT 11
18 R2OUT
T3IN 12
17 R3OUT
T2IN 13
16 R4OUT
T1IN 14
15 R5OUT
SO/SSOP
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
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
Similar pages