MAX221ECUE-T [MAXIM]
Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, PDSO16, 4.40 MM, 0.65 MM PITCH, TSSOP-16;
| 型号： | MAX221ECUE-T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, PDSO16, 4.40 MM, 0.65 MM PITCH, TSSOP-16 驱动 光电二极管 接口集成电路 驱动器 |
| 文件： | 总12页 (文件大小：173K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1527; Rev ꢂ; 8/99
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
MAX21E
General Description
Features
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.
♦ Single RS-232 Transceiver in a Small 16-Pin TSSOP
♦ 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
The MAX221E features enhanced electrostatic discharge
(ESD) protection. Both the transmitter output and receiver
input are protected to 15kV using the ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 Air-
Gap Discharge Method, to 8kV using the ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2
ꢁontact Discharge Method, and to 15kV using the
Human Body Model.
♦ Latchup Free
♦ 1µA Supply Current
♦ AutoShutdown Saves Power without Changes
The MAX221E achieves a low 1µA supply current with
Maxim’s revolutionary AutoShutdown™ feature.
AutoShutdown saves power without changes to the
existing BꢀOS 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.
to BIOS
♦ Guaranteed 250kbps Data Rate
Ordering Information
PART
TEMP. RANGE
ꢂ°ꢁ to +7ꢂ°ꢁ
ꢂ°ꢁ to +7ꢂ°ꢁ
ꢃꢂ°ꢁ to +85°ꢁ
ꢃꢂ°ꢁ to +85°ꢁ
PIN-PACKAGE
16 TSSOP
16 SSOP
MAX221EꢁUE
MAX221EꢁAE
MAX221EEUE
MAX221EEAE
The MAX221E is available in a 16-pin SSOP package as
well as a 16-pin TSSOP that uses 5ꢂ% less board space
than a 16-pin SO.
16 TSSOP
16 SSOP
Applications
Typical Operating Circuit
Maintenance/Diagnostic Ports
ꢀndustrial Systems
+5V
15
Telecommunications
Set-Top Boxes
C3
C
BYPASS
0.1µF
0.1µF
V
CC
3
7
2
C1+
V+
V-
C1
0.1µF
4
5
6
-in Configuration
C1-
C2+
MAX221E
C4
0.1µF
C2
0.1µF
TOP VIEW
C2-
TIN
EN
C1+
V+
1
2
3
4
5
6
7
8
16 FORCEOFF
15
11
TOUT 13
V
CC
14 GND
9
ROUT
RIN
8
C1-
C2+
C2-
V-
MAX221E
13 TOUT
12 FORCEON
11 TIN
5k
TO POWER-
MANAGEMENT
UNIT
10
16
1
10 INVALID
EN
INVALID
RIN
9
ROUT
12
FORCEOFF
V
FORCEON
CC
GND
14
TSSOP/SSOP
CAPACITORS MAY BE
POLARIZED OR UNPOLARIZED.
AutoShutdown is a trademark of Maxim ꢀntegrated Products.
________________________________________________________________ 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 1-800-835-8769.
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
ABSOLUTE MAXIMUM RATINGS
V
..........................................................................-ꢂ.3V to +6V
Short-ꢁircuit Duration, TOUT .....................................ꢁontinuous
ꢁꢁ
V+ ...............................................................(V
- ꢂ.3V) to +1ꢃV
ꢁontinuous Power Dissipation (T = +7ꢂ°ꢁ)
ꢁꢁ
A
V- ...........................................................................-1ꢃV to +ꢂ.3V
ꢀnput Voltages
TꢀN............................................................-ꢂ.3V to (V+ + ꢂ.3V)
RꢀN................................................................................... 3ꢂV
16-Pin TSSOP (derated 6.7mW/°ꢁ above +7ꢂ°ꢁ).......533mW
16-Pin SSOP (derated 7.1mW/°ꢁ above +7ꢂ°ꢁ).........571mW
Operating Temperature Range
MAX221Eꢁ_ _.....................................................ꢂ°ꢁ to +7ꢂ°ꢁ
MAX221EE_ _ ..................................................-ꢃꢂ°ꢁ to +85°ꢁ
Maximum Junction Temperature .................................... +15ꢂ°ꢁ
Storage Temperature Range ........................... -65°ꢁ to +15ꢂ°ꢁ
Lead Temperature (soldering, 1ꢂsec) ............................ +3ꢂꢂ°ꢁ
ꢅORꢁEON, FORCEOFF, EN ..................-ꢂ.3V to (V
+ ꢂ.3V)
ꢁꢁ
Output Voltages
TOUT ................................................(V- - ꢂ.3V) to (V+ + ꢂ.3V)
ROUT, INVALID......................................-ꢂ.3V to (V + ꢂ.3V)
MAX21E
ꢁꢁ
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
(V = +5V 1ꢂ%, ꢁ1ꢄꢁꢃ = ꢂ.1µꢅ, T = T
to T
, unless otherwise noted. Typical values are at T = +25°ꢁ.)
ꢁꢁ
A
MꢀN
MAX A
PARAMETER
DC CHARACTERISTICS
Supply ꢁurrent
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
ꢁꢁ
ꢀ
No load, T = +25°ꢁ
5
1
1
1ꢂ
1ꢂ
1ꢂ
mA
µA
µA
ꢁꢁ
A
Shutdown Supply ꢁurrent
AutoShutdown Supply ꢁurrent
LOGIC INPUTS
ꢀ
T = +25°ꢁ, ꢅigure 1
A
SHDN
ꢀ
AS
ꢀnput Leakage ꢁurrent
ꢀnput Threshold Low
ꢀnput Threshold High
Output Voltage Low
TꢀN = ꢂ to V
1
µA
V
ꢁꢁ
V
V
ꢂ.8
TꢀN, EN, FORCEOFF, ꢅORꢁEON
EN, FORCEOFF, TꢀN
ꢀL
2.ꢃ
3.5
V
ꢀH
OL
OH
V
ROUT; ꢀ
= 3.2mA
ꢂ.ꢃ
1ꢂ
V
SꢀNK
SOURꢁE
Output Voltage High
Output Leakage ꢁurrent
AUTOSHUTDOWN
V
ROUT; ꢀ
= 1.ꢂmA
V
ꢂ.ꢂ5
µA
EN = V , ꢂ ≤ ROUT ≤ V
ꢁꢁ
ꢁꢁ
Positive threshold
Negative threshold
2.7
Receiver ꢀnput Threshold,
Transmitter Enabled
ꢅigure 3
V
V
-2.7
-ꢂ.3
Receiver ꢀnput Threshold,
Transmitter Disabled
ꢀ
= 1µA, ꢅigure 3
= 1.6mA
ꢂ.3
ꢂ.ꢃ
ꢁꢁ
ꢀ
ꢀ
V
V
INVALID Output Voltage Low
INVALID Output Voltage High
SꢀNK
= 1.ꢂmA
V
- ꢂ.6
SOURꢁE
ꢁꢁ
Receiver Threshold to
Transmitter Enabled
t
ꢅigure 3
ꢅigure 3
ꢅigure 3
25ꢂ
1
µs
µs
µs
WU
Receiver Positive or Negative
Threshold to INVALID High
t
ꢀNVH
Receiver Positive or Negative
Threshold to INVALID Low
t
3ꢂ
ꢀNVL
2
_______________________________________________________________________________________
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
MAX21E
ELECTRICAL CHARACTERISTICS (continued)
(V = +5V 1ꢂ%, ꢁ1ꢄꢁꢃ = ꢂ.1µꢅ, T = T
to T , unless otherwise noted. Typical values are at T = +25°ꢁ.)
MAX A
ꢁꢁ
A
MꢀN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
25
UNITS
RECEIVER INPUT
ꢀnput Voltage Range
ꢀnput Threshold Low
ꢀnput Threshold High
ꢀnput Hysteresis
-25
ꢂ.8
V
V
T
T
= +25°ꢁ, V
= +25°ꢁ, V
= 5V
= 5V
1.2
1.7
ꢂ.5
5
A
ꢁꢁ
2.ꢃ
7
V
A
ꢁꢁ
V
= 5V, no hysteresis in shutdown
V
ꢁꢁ
ꢀnput Resistance
T
A
= +25°ꢁ, V = 5V
3
kΩ
ꢁꢁ
TRANSMITTER OUTPUT
Output Voltage Swing
Output Resistance
Driver loaded with 3kΩ to ground
= V+ = V- = ꢂ, V 2V
5
9
V
Ω
V
=
OUT
3ꢂꢂ
ꢁꢁ
Output Short-ꢁircuit ꢁurrent
ESD PROTECTION
1ꢂ
6ꢂ
mA
ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 Air-Gap Discharge
ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 ꢁontact Discharge
Human Body Model
15
8
RꢀN, TOUT
kV
15
TIMING CHARACTERISTICS
(V
ꢁꢁ
= +5V 1ꢂ%, ꢁ1ꢄꢁꢃ = ꢂ.1µꢅ, T = T
to T , unless otherwise noted. Typical values are at T = +25°ꢁ.)
MAX A
A
MꢀN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R = 3kΩ to 7kΩ, ꢁ = 5ꢂpꢅ to 1ꢂꢂꢂpꢅ,
L
L
Maximum Data Rate
25ꢂ
kbps
V
ꢁꢁ
= ꢃ.5V
Receiver Propagation Delay
Receiver Output Enable Time
Receiver Output Disable Time
Transmitter Skew
t
t
ꢁ = 15ꢂpꢅ
L
ꢂ.15
3ꢂꢂ
2ꢂꢂ
2ꢂꢂ
5ꢂ
ms
ns
ns
ns
ns
PHL, PLH
Normal operation
Normal operation
(Note 1)
|t
|t
t
|
|
PHL PLH
Receiver Skew
t
PHL PLH
T
A
= +25°ꢁ, V = 5V, R = 3kΩ to 7kΩ,
ꢁꢁ L
Transition-Region Slew Rate
ꢁ = 5ꢂꢂpꢅ to 1ꢂꢂꢂpꢅ, measured from
L
3
6
3ꢂ
V/µs
-3V to +3V or +3V to -3V
Note 1: Transmitter skew is measured at the transmitter zero crosspoints.
_______________________________________________________________________________________
3
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
Typical Operating Characteristics
(V = +5V, 25ꢂkbps data rate, ꢂ.1µꢅ capacitors, transmitter loaded with 3kΩ and ꢁ , T = +25°ꢁ, unless otherwise noted.)
L
A
ꢁꢁ
TRANSMITTER OUTPUT
VOLTAGE vs. LOAD CAPACITANCE
SLEW RATE vs.
LOAD CAPACITANCE
OPERATING SUPPLY
CURRENT vs. LOAD CAPACITANCE
10
8
50
50
40
6
40
30
20
10
0
MAX21E
20kbps
120kbps
4
+SLEW
250kbps
250kbps
250kbps
2
30
20
10
0
0
-2
-4
-6
-8
-SLEW
2000
120kbps
20kbps
120kbps
1000
20kbps
-10
3000
4000
4000
1000
3000
4000
0
2000
5000
1000
3000
0
5000
0
2000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
-in Description
PIN
NAME
FUNCTION
Receiver Enable ꢁontrol. Drive low for normal operation. Drive high to force the receiver output
(ROUT) into a high-impedance state.
1
EN
2
3
ꢃ
5
6
7
8
9
ꢁ1+
V+
Positive Terminal of the Voltage Doubler ꢁharge-Pump ꢁapacitor
Positive Voltage Generated by the ꢁharge Pump
Negative Terminal of the Voltage Doubler ꢁharge-Pump ꢁapacitor
Positive Terminal of the ꢀnverting ꢁharge-Pump ꢁapacitor
Negative Terminal of the ꢀnverting ꢁharge-Pump ꢁapacitor
Negative Voltage Generated by the ꢁharge Pump
RS-232 Receiver ꢀnput, 15kV ESD protected
ꢁ1-
ꢁ2+
ꢁ2-
V-
RꢀN
ROUT
TTL/ꢁMOS Receiver Output
Output of the ꢀnvalid Signal Detector. INVALID is pulled low if no valid RS-232 level is present on
the receiver input.
1ꢂ
11
12
INVALID
TꢀN
TTL/ꢁMOS Transmitter ꢀnput
Drive high to override automatic circuitry, keeping transmitter and charge pump on. FORCEOFF
must be high (Table 1).
ꢅORꢁEON
13
1ꢃ
15
TOUT
GND
RS-232 Transmitter Output, 15kV ESD Protected
Ground
V
ꢁꢁ
+ꢃ.5V to +5.5V Supply Voltage
ꢅorce-Off ꢀnput, active low. Drive low to shut down transmitter, receiver, and on-board charge
pump. This overrides all automatic circuitry and ꢅORꢁEON (Table 1).
16
FORCEOFF
4
_______________________________________________________________________________________
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
MAX21E
Rꢁꢂ232 Receiver
The MAX221E’s receiver converts RS-232 signals to
ꢁMOS-logic output levels. The receiver has an inverting
three-state output and can be active or inactive. ꢀn
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).
I
SHDN
+5V
15
C3
C
BYPASS
0.1µF
0.1µF
V
CC
3
7
2
C1+
V+
V-
C1
4
5
6
0.1µF
C1-
C2+
MAX221E
C4
0.1µF
C2
0.1µF
C2-
TIN
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
(ꢅigures 2 and 3).
11
TOUT 13
3k
9
ROUT
RIN
8
Autoꢁhutdown
The MAX221E achieves 1µA supply current with
Maxim’s AutoShutdown feature, which operates when
ꢅORꢁEON is low and FORCEOFF is high. When the
device senses no valid signal levels on the receiver
input for 3ꢂµs, the on-board charge pump and driver
are shut off, reducing supply current to 1µA. 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 BꢀOS or
operating system.
5k
TO POWER-
MANAGEMENT
UNIT
10
16
1
EN
INVALID
12
FORCEON
FORCEOFF
GND
14
ꢅigure 1. Shutdown ꢁurrent Test ꢁircuit
Table 1 and ꢅigure 2c summarize the MAX221E operat-
ing modes. ꢅORꢁEON and FORCEOFF override
AutoShutdown. When neither control is asserted, the
device selects between these states automatically,
based on the receiver input level. ꢅigures 2a, 2b, and
3a depict valid and invalid RS-232 receiver levels.
ꢅigure 3 shows the input levels and timing diagram for
AutoShutdown operation.
_______________Detailed Description
Dual Chargeꢂ-ump koltage 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 (ꢁ1, ꢁ2) and a
reservoir capacitor (ꢁ3, ꢁꢃ) to generate the V+ and V-
supplies.
A device or another system with AutoShutdown con-
nected to the MAX221E may need time to wake up.
ꢅigure ꢃ shows a circuit that forces the transmitter on
for 1ꢂꢂms, allowing enough time for the other system to
realize that the MAX221E is awake. ꢀf the other system
transmits valid RS-232 signals within that time, the
RS-232 ports on both systems remain enabled.
Rꢁꢂ232 Transmitter
The transmitter is an inverting level translator that con-
verts ꢁMOS-logic levels to 5.ꢂV EꢀA/TꢀA-232 levels. ꢀt
guarantees a 25ꢂkbps data rate with worst-case loads
of 3kΩ in parallel with 1ꢂꢂꢂpꢅ.
When shut down, the device’s charge pumps turn off,
V+ is pulled to V , V- is pulled to ground, and the
ꢁꢁ
transmitter output is high impedance. The time required
to exit shutdown is typically 1ꢂꢂµs (ꢅigure 3b).
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.
_______________________________________________________________________________________
5
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
Table 1. Output Control Truth Table
OPERATION
STATUS
VALID
RECEIVER
FORCEON
TOUT
ROUT
FORCEOFF
EN
X
X
1
1
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
1
1
1
1
1
1
ꢂ
1
ꢂ
1
ꢂ
1
ꢂ
1
X
X
High-Z
High-Z
Active
Active
Active
Active
High-Z
High-Z
Active
High-Z
Active
High-Z
Active
High-Z
Active
High-Z
Shutdown
(ꢅorced Off)
X
Normal Operation
(ꢅorced On)
X
Yes
Yes
No
No
MAX21E
Normal Operation
(AutoShutdown)
Shutdown
(AutoShutdown)
x = Don’t care
+0.3V
FORCEOFF
POWER DOWN
TO MAX221E
POWER SUPPLY
AND TRANSMITTER
FORCEON
INVALID
RIN
30µs
COUNTER
R
INVALID
-0.3V
INVALID IS AN INTERNALLY GENERATED SIGNAL USED BY
AUTOSHUTDOWN LOGIC AND APPEARS AS AN OUTPUT.
POWER DOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE
OPERATIONAL STATUS OF THE TRANSMITTER AND POWER SUPPLIES.
* TRANSMITTER IS DISABLED, REDUCING SUPPLY CURRENT TO 1µA IF
RECEIVER INPUT IS BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs.
ꢅigure 2c. AutoShutdown Logic
ꢅigure 2a. Entering 1µA Supply Mode via AutoShutdown
+2.7V
TO MAX221E
RIN
POWER SUPPLY
30µs
COUNTER
R
Table 2. INVALID Truth Table
INVALID
RS-232 SIGNAL PRESENT
INVALID OUTPUT
-2.7V
AT RECEIVER INPUT
* TRANSMITTER IS ENABLED IF:
Yes
No
High
Low
RECEIVER INPUT IS GREATER THAN +2.7V OR LESS THAN -2.7V.
RECEIVER INPUT HAS BEEN BETWEEN +0.3V AND -0.3V FOR LESS THAN 30µs.
ꢅigure 2b. Transmitter Enabled Using AutoShutdown
6
_______________________________________________________________________________________
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
MAX21E
ꢁoftwareꢂControlled ꢁhutdown
ꢅor direct software control, use INVALID to indicate a
DTR or Ring ꢀndicator signal. ꢁonnect FORCEOFF and
TRANSMITTER ENABLED, INVALID HIGH
ꢅORꢁEON together to disable AutoShutdown so the
line acts like a SHDN input.
+2.7V
INDETERMINATE
1ꢀ5k EꢁD -rotection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges encountered during handling and
assembly. The driver output and receiver input of the
MAX221E have extra protection against static electrici-
ty. 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.
+0.3V
0
AUTOSHUTDOWN, TRANSMITTER DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
-0.3V
INDETERMINATE
-2.7V
TRANSMITTER ENABLED, INVALID HIGH
a)
RECEIVER
INPUT
VOLTAGE
(V)
INVALID
REGION
ESD protection can be tested in various ways; the trans-
mitter output and receiver input of the MAX221E are
characterized for protection to the following limits:
1) 15kV using the Human Body Model
V
CC
0
2) 8kV using the ꢁontact-Discharge Method
specified in ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2
INVALID
OUTPUT
(V)
3) 15kV using ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2’s Air-Gap Method
t
t
INVH
INVL
t
WU
EꢁD Test Conditions
ESD performance depends on a variety of conditions.
ꢁontact Maxim for a reliability report that documents
test setup, test methodology, and test results.
V+
V
CC
0
V-
Human Body Model
ꢅigure 5a shows the Human Body Model, and ꢅigure
5b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 1ꢂꢂpꢅ capacitor charged to the ESD voltage of inter-
est, which is then discharged into the test device
through a 1.5kΩ resistor.
b)
ꢅigure 3. AutoShutdown Trip Levels
POWER-
MANAGEMENT
UNIT
MASTER SHDN LINE
IEC 1000ꢂ4ꢂ2
The ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 standard covers ESD testing and
performance of finished equipment; it does not specifi-
cally refer to integrated circuits. The MAX221E helps
you design equipment that meets Level ꢃ (the highest
level) of ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2, without the need for additional
ESD-protection components.
0.1µF
1MΩ
FORCEOFF FORCEON
MAX221E
The major difference between tests done using the
Human Body Model and ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 (ꢅigure 6) is
higher peak current in the ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 because series
resistance is lower in the ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 model. Hence,
ꢅigure ꢃ. AutoShutdown with ꢀnitial Turn-On to Wake Up a
Mouse or Another System
_______________________________________________________________________________________
7
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
R
50MΩ to 100MΩ
R 330Ω
D
R
1MΩ
R 1500Ω
D
C
C
DISCHARGE
RESISTANCE
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
CHARGE-CURRENT
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
DEVICE
UNDER
TEST
C
s
100pF
STORAGE
CAPACITOR
C
s
150pF
STORAGE
CAPACITOR
MAX21E
SOURCE
SOURCE
ꢅigure 5a. Human Body ESD Test Model
ꢅigure 6a. ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 ESD Test Model
I
100%
90%
I 100%
P
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
AMPERES
36.8%
10%
0
TIME
0
t
RL
t
DL
10%
t = 0.7ns to 1ns
CURRENT WAVEFORM
r
t
30ns
60ns
ꢅigure 5b. Human Body Model ꢁurrent Waveform
ꢅigure 6b. ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 ESD Generator ꢁurrent Waveform
the ESD that withstands voltage measured to ꢀEꢁ 1ꢂꢂꢂ-
ꢃ-2 is generally lower than that measured using the
Human Body Model. ꢅigure 6a shows the ꢀEEE 1ꢂꢂꢂ-ꢃ-
2 model and ꢅigure 6b shows the current waveform for
the 8kV ꢀEꢁ 1ꢂꢂꢂ-ꢃ-2 Level ꢃ ESD ꢁontact-Discharge
test.
Machine Model
The Machine Model for ESD tests all pins, using a
2ꢂꢂpꢅ storage capacitor and zero discharge resis-
tance. ꢀts objective is to emulate the stress caused not
only by RS-232 inputs and outputs, but also by contact
that occurs due to handling and assembling during
manufacturing. Therefore, after Pꢁ board assembly, the
Machine Model is less relevant to ꢀ/O ports.
The Air-Gap Method involves approaching the device
with a charged probe. The ꢁontact-Discharge Method
connects the probe to the device before the probe is
energized.
8
_______________________________________________________________________________________
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
MAX21E
nominal value. The capacitor’s equivalent series resis-
__________Applications Information
tance (ESR) usually rises at low temperatures and influ-
INVALID
Using
ences the amount of ripple on V+ and V-.
INVALID indicates when an RS-232 signal is present at
the receiver input, and therefore when the port is in use.
INVALID can be used in alternative shutdown control
schemes where it relieves the processor from constantly
polling the part for activity.
-owerꢂꢁupply Decoupling
ꢀn most circumstances, a ꢂ.1µꢅ V bypass capacitor
is adequate. ꢀn applications that are sensitive to power-
supply noise, use a capacitor of the same value as the
charge-pump capacitor ꢁ1. ꢁonnect bypass capaci-
tors as close to the ꢀꢁ as possible.
ꢁꢁ
Capacitor ꢁelection
The capacitor type used for ꢁ1ꢄꢁꢃ is not critical for
proper operation; either polarized or nonpolarized
capacitors are acceptable. ꢀf polarized capacitors are
used, connect polarity as shown in the Typical
Operating ꢁircuit. The charge pump requires ꢂ.1µꢅ
capacitors. ꢀncreasing the capacitor values (e.g., by a
factor of 2) reduces ripple on the transmitter output,
and slightly reduces power consumption. ꢁ2, ꢁ3, and
ꢁꢃ can be increased without changing ꢁ1’s value.
However, do not increase ꢁ1’s value without also
increasing the values of ꢁ2, ꢁ3, and ꢁꢃ to maintain the
proper ratios (ꢁ1 to the other capacitors).
Transmitter Output when
Exiting ꢁhutdown
ꢅigure 7 shows the transmitter output when exiting
shutdown mode. The transmitter is loaded with 3kΩ in
parallel with 1ꢂꢂꢂpꢅ. The transmitter output displays no
ringing or undesirable transients as the MAX221E
comes out of shutdown.
High Data Rates
The MAX221E maintains the RS-232 5.ꢂV minimum
transmitter output voltage even at high data rates.
ꢅigure 8 shows a transmitter loopback test circuit.
ꢅigure 9 shows the loopback test result at 12ꢂkbps,
and ꢅigure 1ꢂ shows the same test at 25ꢂkbps.
When using the minimum ꢂ.1µꢅ capacitors, make sure
the capacitance does not degrade excessively with
temperature. ꢀf in doubt, use capacitors with a larger
+5V
0.1µF
5V/div
5V/div
FORCEON =
FORCEOFF
C3
TIN = GND
V
CC
C1+
V+
V-
C1
C2
C1-
C2+
MAX221E
TOUT
C4
C2-
TIN
TIN = V
CC
TOUT
RIN
ROUT
EN
50µs/div
1000pF
5k
0V
ꢅigure 7. Transmitter Output when Exiting Shutdown or
Powering Up
V
CC
FORCEOFF
FORCEON
INVALID
GND
ꢅigure 8. Loopback Test ꢁircuit
_______________________________________________________________________________________
9
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
TIN
5V/div
TIN
5V/div
TOUT
ROUT
5V/div
5V/div
5V/div
5V/div
TOUT
ROUT
MAX21E
2µs/div
2µs/div
ꢅigure 9. Loopback Test Result at 12ꢂkbps
ꢅigure 1ꢂ. Loopback Test Result at 25ꢂkbps
___________________Chip Information
TRANSꢀSTOR ꢁOUNT: 157
10 ______________________________________________________________________________________
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
MAX21E
-ac5age Information
______________________________________________________________________________________ 11
1ꢀ5k EꢁDꢂ-rotected, +ꢀk, 1µA, ꢁingle Rꢁꢂ232
Transceiver with Autoꢁhutdown
-ac5age Information (continued)
MAX21E
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated -roducts, 120 ꢁan Gabriel Drive, ꢁunnyvale, CA 94086 408ꢂ737ꢂ7600
© 1999 Maxim ꢀntegrated Products
Printed USA
is a registered trademark of Maxim ꢀntegrated Products.
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