MAX221ECUE+ [MAXIM]
Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, CMOS, PDSO16, 4.40 MM, 0.65 MM PITCH, TSSOP-16;
| 型号： | MAX221ECUE+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, CMOS, PDSO16, 4.40 MM, 0.65 MM PITCH, TSSOP-16 |
| 文件： | 总8页 (文件大小：112K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1520; Rev 0; 8/99
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
MAX21
General Description
Features
The MAX221 is a +5V-powered, single transmit/receive
RS-232 and V.28 communications interface with auto-
matic shutdown/wake-up features and high data rate
capabilities.
♦ Single RS-232 Transceiver in a Small 16-Pin
TSSOP Package
♦ 1µA Supply Current
The MAX221 achieves a low 1µA supply current with
Maxim’s revolutionary AutoShutdown™ 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 MAX221 wakes up and drives the
INVALID pin high when an active RS-232 cable is con-
nected, signaling the host that a peripheral is connect-
ed to the communications port.
♦ AutoShutdown Saves Power Without
Changes to BIOS
♦ Guaranteed 250kbps Data Rate
Ordering Information
The MAX221 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. For an equivalent RS-232 transceiver
with enhanced 15kV ꢀSꢁ protection, refer to the
MAX221ꢀ data sheet.
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 TSSOP
16 SSOP
MAX221CUꢀ
MAX221CAꢀ
MAX221ꢀUꢀ
MAX221ꢀAꢀ
16 TSSOP
16 SSOP
Applications
Maintenance/ꢁiagnostic Ports
Industrial Systems
Telecommunications
Set-Top Boxes
Typical Operating Circuit
+5V
15
C3
0.1µF
C
BYPASS
0.1µF
V
CC
Pin Configuration
3
7
2
C1+
V+
V-
C1
0.1µF
4
5
6
C1-
C2+
TOP VIEW
MAX221
C4
0.1µF
EN
C1+
V+
1
2
3
4
5
6
7
8
16 FORCEOFF
15
C2
0.1µF
C2-
TIN
V
CC
11
TOUT 13
14 GND
C1-
C2+
C2-
V-
MAX221
13 TOUT
12 FORCEON
11 TIN
9
ROUT
RIN
8
5k
10 INVALID
TO POWER-
MANAGEMENT
UNIT
RIN
9
ROUT
10
16
1
EN
INVALID
TSSOP/SSOP
12
FORCEOFF
V
FORCEON
CC
GND
14
CAPACITORS MAY BE POLARIZED OR UNPOLARIZED.
AutoShutdown is a trademark of Maxim Integrated 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.
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
ABSOLUTE MAXIMUM RATINGS
V
CC
..........................................................................-0.3V to +6V
Short-Circuit ꢁuration, TOUT .....................................Continuous
V+ ...............................................................(V
- 0.3V) to +14V
Continuous Power ꢁissipation (T = +70°C)
CC
A
V- ...........................................................................-14V to +0.3V
Input Voltages
TSSOP (derated 6.7mW/°C above +70°C) ................533mW
SSOP (derated 7.1mW/°C above +70°C) ..................571mW
Operating Temperature Range
MAX221C_ _ .....................................................0°C to +70°C
MAX221ꢀ_ _ ..................................................-40°C to +85°C
Maximum Junction Temperature ................................... +150°C
Storage Temperature Range ........................... -65°C to +150°C
Lead Temperature (soldering, 10sec) ............................ +300°C
TIN..........................................................-0.3V to (V+ + 0.3V)
RIN................................................................................. 30V
FORCꢀON, FORCEOFF, EN.................-0.3V to (V
+ 0.3V)
CC
MAX21
Output Voltages
TOUT ..............................................(V- - 0.3V) to (V+ + 0.3V)
ROUT, INVALID....................................-0.3V to (V + 0.3V)
CC
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. ꢀxposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V = +5V 10%, C1ꢂC4 = 0.1µF, T = T
to T
, unless otherwise noted. Typical values are at T = +25°C.)
CC
A
MIN
MAX A
PARAMETER
DC CHARACTERISTICS
Supply Current
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
I
No load, T = +25°C
5
1
1
10
10
10
mA
µA
µA
CC
A
Shutdown Supply Current
AutoShutdown Supply Current
LOGIC INPUTS
I
T = +25°C, Figure 1
A
SHꢁN
I
AS
Input Leakage Current
Input Threshold Low
Input Threshold High
Output Voltage Low
I
TIN = 0 to V
1
µA
V
IN
CC
V
V
0.8
TIN; EN, FORCEOFF, FORCꢀON
TIN, EN, FORCEOFF
IL
2.4
3.5
V
IH
OL
OH
V
ROUT; I
= 3.2mA
0.4
10
V
SINK
SOURCꢀ
Output Voltage High
Output Leakage Current
AUTOSHUTDOWN
V
ROUT; I
= 1.0mA
V
0.05
µA
EN = V , 0 ≤ ROUT ≤ V
CC
CC
Positive threshold
Negative threshold
2.7
Receiver Input Threshold,
Transmitter ꢀnabled
Figure 3
V
V
-2.7
-0.3
Receiver Input Threshold,
Transmitter ꢁisabled
I
= 1µA, Figure 3
= 1.6mA
0.3
0.4
CC
I
I
V
V
INVALID Output Voltage Low
INVALID Output Voltage High
SINK
= 1.0mA
V
- 0.6
SOURCꢀ
CC
Receiver Threshold to
Transmitter ꢀnabled
t
Figure 3
Figure 3
Figure 3
250
1
µs
µs
µs
WU
Receiver Positive or Negative
Threshold to INVALID High
t
INVH
Receiver Positive or Negative
Threshold to INVALID Low
t
30
INVL
2
_______________________________________________________________________________________
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
MAX21
ELECTRICAL CHARACTERISTICS (continued)
(V = +5V 10%, C1ꢂC4 = 0.1µF, T = T
to T , unless otherwise noted. Typical values are at T = +25°C.)
MAX A
CC
A
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
25
UNITS
RECEIVER INPUT
Input Voltage Range
Input Threshold Low
Input Threshold High
Input Hysteresis
-25
0.8
V
V
T
T
= +25°C, V
= +25°C, V
= 5V
= 5V
1.2
1.7
0.5
5
A
CC
2.4
7
V
A
CC
V
= 5V, no hysteresis in shutdown
V
CC
Input Resistance
T
A
= +25°C, V = 5V
3
kΩ
CC
TRANSMITTER OUTPUT
Output Voltage Swing
Output Resistance
ꢁriver loaded with 3kΩ to ground
= V+ = V- = 0, V 2V
5
9
V
Ω
V
=
OUT
300
CC
Output Short-Circuit Current
10
60
mA
TIMING CHARACTERISTICS
(V
CC
= +5V 10%, C1ꢂC4 = 0.1µF, T = T
to T , unless otherwise noted. Typical values are at T = +25°C.)
MAX A
A
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R = 3kΩ to 7kΩ, C = 50pF to 1000pF,
L
L
Maximum ꢁata Rate
250
kbps
V
CC
= 4.5V
Receiver Propagation ꢁelay
Receiver Output ꢀnable Time
Receiver Output ꢁisable Time
Transmitter Skew
t
t
C = 150pF
L
0.15
300
200
200
50
µs
ns
ns
ns
ns
PHL, PLH
Normal operation
Normal operation
(Note 1)
t
- t
| PHL PLH|
Receiver Skew
t
- t
| PHL PLH|
T
A
= +25°C, V
= 5V, R = 3kΩ to 7kΩ,
CC L
Transition-Region Slew Rate
C = 500pF to 1000pF, measured from
L
3
6
30
V/µs
-3V to +3V or +3V to -3V
Note 1: Transmitter skew is measured at the transmitter zero crosspoints.
_______________________________________________________________________________________
3
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
Typical Operating Characteristics
(V
CC
= +5V, 250kbps data rate, 0.1µF capacitors, transmitter loaded with 3kΩ and C , T = +25°C, unless otherwise noted.)
L
A
SLEW RATE vs.
LOAD CAPACITANCE
OPERATING SUPPLY
CURRENT vs. LOAD CAPACITANCE
TRANSMITTER OUTPUT
VOLTAGE vs. LOAD CAPACITANCE
50
40
50
10
8
6
40
30
20
10
MAX21
20kbps
250kbps
120kbps
4
+SLEW
-SLEW
250kbps
250kbps
2
30
20
0
-2
-4
-6
-8
120kbps
20kbps
10
0
120kbps
2000
20kbps
0
-10
4000
LOAD CAPACITANCE (pF)
4000
1000
3000
1000
3000
1000
3000
4000
0
2000
5000
0
5000
0
2000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
Pin Description
PIN
NAME
FUNCTION
Receiver ꢀnable Control. ꢁrive low for normal operation. ꢁrive high to force the receiver output
(ROUT) into a high-impedance state.
1
EN
2
3
4
5
6
7
8
9
C1+
V+
Positive Terminal of the Voltage ꢁoubler Charge-Pump Capacitor
Positive Voltage Generated by the Charge Pump
Negative Terminal of the Voltage ꢁoubler Charge-Pump Capacitor
Positive Terminal of the Inverting Charge-Pump Capacitor
Negative Terminal of the Inverting Charge-Pump Capacitor
Negative Voltage Generated by the Charge Pump
RS-232 Receiver Input
C1-
C2+
C2-
V-
RIN
ROUT
TTL/CMOS Receiver Output
Output of the Invalid Signal ꢁetector. INVALID is pulled low if no valid RS-232 level is present on
the receiver input.
10
11
12
INVALID
TIN
TTL/CMOS Transmitter Input
ꢁrive high to override automatic circuitry, keeping transmitter and charge pump on.
FORCEOFF must be high (Table 1).
FORCꢀON
13
14
15
TOUT
GNꢁ
RS-232 Transmitter Output
Ground
V
CC
+4.5V to +5.5V Supply Voltage
Force-Off Input, active low. ꢁrive low to shut down transmitter, receiver, and on-board charge
pump. This overrides all automatic circuitry and FORCꢀON (Table 1).
16
FORCEOFF
4
_______________________________________________________________________________________
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
MAX21
three-state output and can be active or inactive. In shut-
I
SHDN
down (FORCEOFF = low) or in AutoShutdown, the
+5V
15
receiver is active (Table 1). ꢁrive EN high to place the
C3
0.1µF
C
BYPASS
0.1µF
receiver in a high-impedance state. The receiver is high
V
CC
3
2
C1+
impedance when the MAX221 is in shutdown (FORCE-
V+
C1
0.1µF
OFF = low).
4
5
6
C1-
C2+
MAX221
The MAX221’s INVALID output is pulled low when no
valid RS-232 signal level is detected on the receiver
input. INVALID is functional in any mode (Figures 2
and 3).
7
V-
C4
0.1µF
C2
0.1µF
C2-
TIN
11
TOUT 13
AutoShutdown
The MAX221 achieves 1µA supply current with Maxim’s
AutoShutdown feature, which operates when FORCꢀON
is low and FORCEOFF is high. When the device senses
no valid signal levels on the receiver input for 30µs, 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 connected peripheral transmitter is
turned off. The MAX221 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.
3k
9
ROUT
RIN
8
5k
TO POWER-
MANAGEMENT
UNIT
10
16
1
EN
INVALID
12
FORCEOFF
FORCEON
GND
14
Figure 1. Shutdown Current Test Circuit
Table 1 and Figure 2c summarize the MAX221 operat-
ing modes. FORCꢀON 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.
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX221’s internal power supply consists of a dual
charge pump that provides a positive output voltage
(doubling charge pump) and a negative voltage (invert-
ing charge pump) from a single +5V supply. The
charge pumps operate in continuous mode. ꢀach
charge pump requires a flying capacitor (C1, C2) and a
reservoir capacitor (C3, C4) to generate the V+ and V-
supplies.
A device or another system with AutoShutdown con-
nected to the MAX221 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 MAX221 is awake. If the other system
transmits valid RS-232 signals within that time, the RS-
232 ports on both systems remain enabled.
RS-232 Transmitter
The transmitter is an inverting level translator that con-
verts CMOS-logic levels to 5.0V ꢀIA/TIA-232 levels. It
guarantees a 250kbps data rate with worst-case loads
of 3kΩ in parallel with 1000pF.
When shut down, the device’s charge pumps are off,
V+ is pulled to V , V- is pulled to ground, and the
CC
transmitter output is high impedance. The time required
to exit shutdown is typically 100µs (Figure 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 out-
put is forced into a high-impedance state. The transmitter
input does not have a pull-up resistor.
Software-Controlled Shutdown
For direct software control, use INVALID to indicate a
ꢁTR or Ring Indicator signal. Connect FORCEOFF and
FORCꢀON together to disable AutoShutdown so the
line acts like a SHDN input.
RS-232 Receiver
The MAX221’s receiver converts RS-232 signals to
CMOS-logic output levels. The receiver has an inverting
_______________________________________________________________________________________
5
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
Table 1. Output Control Truth Table
VALID
RECEIVER
LEVEL
OPERATION
STATUS
FORCEON
TOUT
ROUT
FORCEOFF
EN
X
X
1
1
0
0
0
0
0
0
1
1
1
1
1
1
0
1
0
1
0
1
0
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
(Forced Off)
MAX21
X
Normal Operation
(Forced On)
X
Yes
Yes
No
No
Normal Operation
(AutoShutdown)
Shutdown
(AutoShutdown)
X = ꢁon’t care
FORCEOFF
+0.3V
POWER DOWN
FORCEON
INVALID
TO MAX221
POWER SUPPLY
RIN
AND TRANSMITTER
30µs
COUNTER
R
INVALID
-0.3V
INVALID IS AN INTERNALLY GENERATED SIGNAL USED BY
THE AUTOSHUTDOWN LOGIC AND APPEARS AS AN OUTPUT.
* TRANSMITTER IS DISABLED, REDUCING SUPPLY CURRENT TO 1µA IF
RECEIVER INPUT IS BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs.
POWER DOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE
OPERATIONAL STATUS OF THE TRANSMITTER AND POWER SUPPLIES.
Figure 2a. ꢀntering 1µA Supply Mode via AutoShutdown
Figure 2c. AutoShutdown Logic
Table 2. INVALID Truth Table
+2.7V
RS-232 SIGNAL PRESENT
INVALID OUTPUT
AT RECEIVER INPUT
TO MAX221
RIN
POWER SUPPLY
Yes
No
High
Low
30µs
COUNTER
R
INVALID
-2.7V
* TRANSMITTER IS ENABLED IF:
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.
Figure 2b. Transmitter ꢀnabled Using AutoShutdown
6
_______________________________________________________________________________________
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
MAX21
Applications Information
Using INVALID
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 port for activity.
TRANSMITTER ENABLED, INVALID HIGH
+2.7V
INDETERMINATE
+0.3V
0
AUTOSHUTDOWN, TRANSMITTER DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
Capacitor Selection
The capacitor type used for C1ꢂC4 is not critical for
proper operation; either polarized or nonpolarized
capacitors are acceptable. If polarized capacitors are
used, connect polarity as shown in the Typical Operating
Circuit. The charge pump requires 0.1µF capacitors.
Increasing the capacitor values (e.g., by a factor of 2)
reduces ripple on the transmitter output and slightly
reduces power consumption. C2, C3, and C4 can be
increased without changing C1’s value. However, do not
increase C1’s value without also increasing the values of
C2, C3, and C4 to maintain the proper ratios (C1 to the
other capacitors).
-0.3V
INDETERMINATE
-2.7V
TRANSMITTER ENABLED, INVALID HIGH
a)
RECEIVER
INPUT
VOLTAGE
(V)
INVALID
REGION
When using the minimum 0.1µF capacitors, make sure
the capacitance does not degrade excessively with
temperature. If in doubt, use capacitors with a larger
nominal value. The capacitor’s equivalent series resis-
tance (ꢀSR) usually rises at low temperatures and influ-
ences the amount of ripple on V+ and V-.
V
CC
INVALID
OUTPUT
(V)
0
t
t
INVH
INVL
Power-Supply Decoupling
t
WU
In most circumstances, a 0.1µF V
bypass capacitor
CC
is adequate. In applications that are sensitive to power-
supply noise, use a capacitor of the same value as the
charge-pump capacitor C1. Connect bypass capaci-
tors as close to the IC as possible.
V+
V
CC
0
V-
Transmitter Output when
Exiting Shutdown
b)
Figure 5 shows the transmitter output when exiting shut-
down mode. The transmitter is loaded with 3kΩ in paral-
lel with 2500pF. The transmitter output displays no
ringing or undesirable transients as the MAX221 comes
out of shutdown. Note that the transmitter is enabled only
when the magnitude of V- exceeds approximately 3V.
Figure 3. AutoShutdown Trip Levels
POWER-
MANAGEMENT
UNIT
MASTER SHDN LINE
0.1µF
1MΩ
High Data Rates
The MAX221 maintains the RS-232 5.0V minimum
transmitter output voltage even at high data rates.
Figure 6 shows a transmitter loopback test circuit.
Figure 7 shows the loopback test result at 120kbps,
and Figure 8 shows the same test at 250kbps.
FORCEOFF FORCEON
MAX221
Figure 4. AutoShutdown with Initial Turn-On to Wake Up a
Mouse or Another System
_______________________________________________________________________________________
7
+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
FORCEON =
5V/div
FORCEOFF
TIN
5V/div
TIN = GND
5V/div
5V/div
5V/div
TOUT
TOUT
ROUT
MAX21
TIN = V
CC
2µs/div
50µs/div
Figure 5. Transmitter Output ꢀxiting Shutdown or
Powering Up
Figure 7. Loopback Test Result at 120kbps
+5V
5V/div
TIN
0.1µF
C3
C4
V
CC
C1+
V+
V-
C1
C2
C1-
C2+
TOUT
ROUT
5V/div
5V/div
MAX221
C2-
TIN
TOUT
RIN
ROUT
EN
2µs/div
Figure 8. Loopback Test Result at 250kbps
5k
0V
1000pF
V
CC
FORCEOFF
FORCEON
INVALID
GND
___________________Chip Information
TRANSISTOR COUNT: 157
Figure 6. Loopback Test Circuit
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.
8 _____________________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.
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