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General Description
The MAX221E is a +5V powered, single transmit/
receive RS-232 and V.28 communications interface with
automatic shutdown/wake-up features and high data
rate capabilities.
The MAX221E features enhanced electrostatic discharge
(ESD) protection. Both the transmitter output and receiver
input are protected to 15kV using the IEC 1000-4-2 Air-
Gap Discharge Method, to 8kV using the IEC 1000-4-2
Contact Discharge Method, and to 15kV using the
Human Body Model.
The MAX221E achieves a low 1A supply current with
Maxim's revolutionary AutoShutdownTM feature.
AutoShutdown saves power without changes to the
existing BIOS or operating system by entering low-
power shutdown mode when the RS-232 cable is dis-
connected or when the transmitter of the connected
peripheral is off. The MAX221E wakes up and drives the
INVALID pin high when an active RS-232 cable is con-
nected, signaling the host that a peripheral is connected
to the communications port.
The MAX221E is available in a 16-pin SSOP package as
well as a 16-pin TSSOP that uses 50% less board space
than a 16-pin SO.
Applications
Maintenance/Diagnostic Ports
Industrial Systems
Telecommunications
Set-Top Boxes
Features
o
Single RS-232 Transceiver in a Small 16-Pin TSSOP
o
ESD Protection for RS-232 I/O Pins
15kV--Human Body Model
8kV--IEC 1000-4-2, Contact Discharge
15kV--IEC 1000-4-2, Air-Gap Discharge
o
Latchup Free
o
1A Supply Current
o
AutoShutdown Saves Power without Changes
to BIOS
o
Guaranteed 250kbps Data Rate
MAX221E
15kV ESD-Protected, +5V, 1A, Single RS-232
Transceiver with AutoShutdown
________________________________________________________________
Maxim Integrated Products
1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
EN
FORCEOFF
V
CC
GND
TOUT
FORCEON
TIN
INVALID
ROUT
TOP VIEW
MAX221E
TSSOP/SSOP
C1+
V+
C2-
C1-
C2+
V-
RIN
MAX221E
FORCEON
EN
12
1
ROUT
9
FORCEOFF
16
INVALID
10
GND
14
TIN
11
C2-
6
C2+
5
C1-
4
C1+
2
RIN 8
TOUT 13
V-
7
V+
3
V
CC
V
CC
C4
0.1
F
C3
0.1
F
15
C1
0.1
F
C2
0.1
F
C
BYPASS
0.1
F
+5V
TO POWER-
MANAGEMENT
UNIT
CAPACITORS MAY BE
POLARIZED OR UNPOLARIZED.
5k
Typical Operating Circuit
19-1527; Rev 0; 8/99
PART
MAX221ECUE
MAX221ECAE
MAX221EEUE
40C to +85C
0C to +70C
0C to +70C
TEMP. RANGE
PIN-PACKAGE
16 TSSOP
16 SSOP
16 TSSOP
Pin Configuration
Ordering Information
AutoShutdown is a trademark of Maxim Integrated Products.
MAX221EEAE
40C to +85C
16 SSOP
MAX221E
15kV ESD-Protected, +5V, 1A, Single RS-232
Transceiver with AutoShutdown
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
CC
= +5V 10%, C1C4 = 0.1F, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25C.)
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.
V
CC
..........................................................................-0.3V to +6V
V+ ...............................................................(V
CC
- 0.3V) to +14V
V- ...........................................................................-14V to +0.3V
Input Voltages
TIN ............................................................-0.3V to (V+ + 0.3V)
RIN ...................................................................................30V
FORCEON, FORCEOFF, EN ..................-0.3V to (V
CC
+ 0.3V)
Output Voltages
TOUT ................................................(V- - 0.3V) to (V+ + 0.3V)
ROUT, INVALID ......................................-0.3V to (V
CC
+ 0.3V)
Short-Circuit Duration, TOUT .....................................Continuous
Continuous Power Dissipation (T
A
= +70C)
16-Pin TSSOP (derated 6.7mW/C above +70C) .......533mW
16-Pin SSOP (derated 7.1mW/C above +70C) .........571mW
Operating Temperature Range
MAX221EC_ _. ....................................................0C to +70C
MAX221EE_ _ ..................................................-40C to +85C
Maximum Junction Temperature .................................... +150C
Storage Temperature Range ........................... -65C to +150C
Lead Temperature (soldering, 10sec) ............................ +300C
Figure 3
Figure 3
No load, T
A
= +25C
Figure 3
I
SOURCE
= 1.0mA
I
SINK
= 1.6mA
CONDITIONS
I
CC
= 1A, Figure 3
ROUT; I
SINK
= 3.2mA
Figure 3
TIN, EN, FORCEOFF, FORCEON
T
A
= +25C, Figure 1
EN = V
CC
, 0
ROUT
V
CC
TIN = 0 to V
CC
ROUT; I
SOURCE
= 1.0mA
s
30
t
INVL
Receiver Positive or Negative
Threshold to INVALID Low
s
1
t
INVH
Receiver Positive or Negative
Threshold to INVALID High
s
250
t
WU
Receiver Threshold to
Transmitter Enabled
V
V
CC
- 0.6
INVALID Output Voltage High
V
0.4
INVALID Output Voltage Low
V
-0.3
0.3
Receiver Input Threshold,
Transmitter Disabled
-2.7
Positive threshold
V
2.7
Receiver Input Threshold,
Transmitter Enabled
A
0.05
10
Negative threshold
Output Leakage Current
V
3.5
V
OH
Output Voltage High
mA
5
10
I
CC
V
CC
Supply Current
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
V
0.4
V
OL
Output Voltage Low
V
0.8
V
IL
Input Threshold Low
A
1
10
I
SHDN
Shutdown Supply Current
A
1
10
I
AS
AutoShutdown Supply Current
A
1
Input Leakage Current
EN, FORCEOFF, TIN
V
2.4
V
IH
Input Threshold High
DC CHARACTERISTICS
LOGIC INPUTS
AUTOSHUTDOWN
MAX221E
15kV ESD-Protected, +5V, 1A, Single RS-232
Transceiver with AutoShutdown
_______________________________________________________________________________________
3
TIMING CHARACTERISTICS
(V
CC
= +5V 10%, C1C4 = 0.1F, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25C.)
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +5V 10%, C1C4 = 0.1F, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25C.)
Note 1:
Transmitter skew is measured at the transmitter zero crosspoints.
R
L
= 3k
to 7k
, C
L
= 50pF to 1000pF,
V
CC
= 4.5V
CONDITIONS
kbps
250
Maximum Data Rate
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
T
A
= +25C, V
CC
= 5V, R
L
= 3k
to 7k
,
C
L
= 500pF to 1000pF, measured from
-3V to +3V or +3V to -3V
(Note 1)
Normal operation
Normal operation
C
L
= 150pF
V/s
3
6
30
Transition-Region Slew Rate
ns
50
| t
PHL
t
PLH
|
Receiver Skew
ns
200
| t
PHL
t
PLH
|
Transmitter Skew
ns
200
Receiver Output Disable Time
ns
300
Receiver Output Enable Time
ms
0.15
t
PHL,
t
PLH
Receiver Propagation Delay
CONDITIONS
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
V
CC
= V+ = V- = 0, V
OUT
= 2V
Driver loaded with 3k
to ground
T
A
= +25C, V
CC
= 5V
V
CC
= 5V, no hysteresis in shutdown
T
A
= +25C, V
CC
= 5V
T
A
= +25C, V
CC
= 5V
mA
10
60
Output Short-Circuit Current
300
Output Resistance
V
5
9
Output Voltage Swing
k
3
5
7
Input Resistance
V
0.5
Input Hysteresis
V
1.7
2.4
Input Threshold High
V
0.8
1.2
Input Threshold Low
V
-25
25
Input Voltage Range
IEC 1000-4-2 Air-Gap Discharge
kV
15
RIN, TOUT
IEC 1000-4-2 Contact Discharge
8
Human Body Model
15
RECEIVER INPUT
TRANSMITTER OUTPUT
ESD PROTECTION
MAX221E
15kV ESD-Protected, +5V, 1A, Single RS-232
Transceiver with AutoShutdown
4
_______________________________________________________________________________________
0
10
20
30
40
50
0
1000
2000
3000
4000
5000
SLEW RATE vs.
LOAD CAPACITANCE
MAX221Etoc02
LOAD CAPACITANCE (pF)
SLEW RATE (V/
s)
+SLEW
-SLEW
NAME
FUNCTION
1
EN
Receiver Enable Control. Drive low for normal operation. Drive high to force the receiver output
(ROUT) into a high-impedance state.
2
C1+
Positive Terminal of the Voltage Doubler Charge-Pump Capacitor
PIN
3
V+
Positive Voltage Generated by the Charge Pump
4
C1-
Negative Terminal of the Voltage Doubler Charge-Pump Capacitor
8
RIN
RS-232 Receiver Input, 15kV ESD protected
7
V-
Negative Voltage Generated by the Charge Pump
6
C2-
Negative Terminal of the Inverting Charge-Pump Capacitor
5
C2+
Positive Terminal of the Inverting Charge-Pump Capacitor
13
TOUT
RS-232 Transmitter Output, 15kV ESD Protected
12
FORCEON
Drive high to override automatic circuitry, keeping transmitter and charge pump on. FORCEOFF
must be high (Table 1).
11
TIN
TTL/CMOS Transmitter Input
10
INVALID
Output of the Invalid Signal Detector. INVALID is pulled low if no valid RS-232 level is present on
the receiver input.
9
ROUT
TTL/CMOS Receiver Output
Pin Description
14
GND
Ground
15
V
CC
+4.5V to +5.5V Supply Voltage
16
FORCEOFF
Force-Off Input, active low. Drive low to shut down transmitter, receiver, and on-board charge
pump. This overrides all automatic circuitry and FORCEON (Table 1).
-10
-6
-8
-2
-4
2
0
4
8
6
10
0
1000
2000
3000
4000
5000
TRANSMITTER OUTPUT
VOLTAGE vs. LOAD CAPACITANCE
MAX221Etoc01
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
250kbps
250kbps
120kbps
20kbps
20kbps
120kbps
0
10
20
30
40
50
0
1000
2000
3000
4000
5000
OPERATING SUPPLY
CURRENT vs. LOAD CAPACITANCE
MAX221Etoc03
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
250kbps
20kbps
120kbps
Typical Operating Characteristics
(V
CC
= +5V, 250kbps data rate, 0.1F capacitors, transmitter loaded with 3k
and C
L
, T
A
= +25C, unless otherwise noted.)
MAX221E
15kV ESD-Protected, +5V, 1A, Single RS-232
Transceiver with AutoShutdown
_______________________________________________________________________________________
5
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX221E's internal power supply consists of a
dual charge pump that provides a positive output volt-
age (doubling charge pump) and negative output volt-
age (inverting charge pump) from a single +5V supply.
The charge pumps operate in continuous mode. Each
charge pump requires a flying capacitor (C1, C2) and a
reservoir capacitor (C3, C4) to generate the V+ and V-
supplies.
RS-232 Transmitter
The transmitter is an inverting level translator that con-
verts CMOS-logic levels to 5.0V EIA/TIA-232 levels. It
guarantees a 250kbps data rate with worst-case loads
of 3k
in parallel with 1000pF.
When FORCEOFF is driven to ground, or when the
AutoShutdown circuitry senses invalid voltage levels on
the receiver input, the transmitter is disabled and the
output is forced into a high-impedance state. The trans-
mitter input does not have a pull-up resistor.
RS-232 Receiver
The MAX221E's receiver converts RS-232 signals to
CMOS-logic output levels. The receiver has an inverting
three-state output and can be active or inactive. In
shutdown (FORCEOFF = low) or in AutoShutdown, the
receiver is active (Table 1). Drive EN high to place the
receiver in a high-impedance state. The receiver is
high-impedance when the MAX221E is in shutdown
(FORCEOFF = low).
The MAX221E's INVALID output is pulled low when
there is no valid RS-232 signal level detected on the
receiver input. INVALID is functional in any mode
(Figures 2 and 3).
AutoShutdown
The MAX221E achieves 1A supply current with
Maxim's AutoShutdown feature, which operates when
FORCEON is low and FORCEOFF is high. When the
device senses no valid signal levels on the receiver
input for 30s, the on-board charge pump and driver
are shut off, reducing supply current to 1A. This
occurs if the RS-232 cable is disconnected or the con-
nected peripheral transmitter is turned off. The
MAX221E turns on again when a valid level is applied
to the RS-232 receiver input. As a result, the system
saves power without changes to the existing BIOS or
operating system.
Table 1 and Figure 2c summarize the MAX221E operat-
ing modes. FORCEON and FORCEOFF override
AutoShutdown. When neither control is asserted, the
device selects between these states automatically,
based on the receiver input level. Figures 2a, 2b, and
3a depict valid and invalid RS-232 receiver levels.
Figure 3 shows the input levels and timing diagram for
AutoShutdown operation.
A device or another system with AutoShutdown con-
nected to the MAX221E may need time to wake up.
Figure 4 shows a circuit that forces the transmitter on
for 100ms, allowing enough time for the other system to
realize that the MAX221E is awake. If the other system
transmits valid RS-232 signals within that time, the
RS-232 ports on both systems remain enabled.
When shut down, the device's charge pumps turn off,
V+ is pulled to V
CC
, V- is pulled to ground, and the
transmitter output is high impedance. The time required
to exit shutdown is typically 100s (Figure 3b).
MAX221E
FORCEON
EN
12
1
ROUT
I
SHDN
9
FORCEOFF
16
INVALID
10
GND
14
TIN
11
C2-
6
C2+
5
C1-
4
C1+
2
RIN 8
TOUT 13
V-
7
V+
3
V
CC
C4
0.1
F
15
C1
0.1
F
C2
0.1
F
C
BYPASS
0.1
F
+5V
TO POWER-
MANAGEMENT
UNIT
5k
3k
C3
0.1
F
Figure 1. Shutdown Current Test Circuit
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