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19-1527; Rev 0; 8/99
15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown
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 AirGap 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 lowpower shutdown mode when the RS-232 cable is disconnected 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 connected, 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.
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
Ordering Information
PART MAX221ECUE MAX221ECAE MAX221EEUE MAX221EEAE TEMP. RANGE 0C to +70C 0C to +70C 40C to +85C 40C to +85C PIN-PACKAGE 16 TSSOP 16 SSOP 16 TSSOP 16 SSOP
Applications
Maintenance/Diagnostic Ports Industrial Systems Telecommunications Set-Top Boxes
CBYPASS 0.1F +5V
Typical Operating Circuit
15 2 C1+ 4 C15 C2+ C2TOUT 13 VCC V+ 3 C3 0.1F
Pin Configuration
TOP VIEW
EN 1 C1+ 2 V+ 3 C1- 4 C2+ 5 C2- 6 V- 7 RIN 8 16 FORCEOFF 15 VCC 14 GND
C1 0.1F
MAX221E
V-
7 C4 0.1F
C2 0.1F
6
11 TIN
9 ROUT 5k
RIN 8
MAX221E
13 TOUT 12 FORCEON 11 TIN 10 INVALID 9 ROUT 12 FORCEON GND 14 FORCEOFF 16 1 EN INVALID 10 TO POWERMANAGEMENT UNIT VCC
TSSOP/SSOP
AutoShutdown is a trademark of Maxim Integrated Products.
CAPACITORS MAY BE POLARIZED OR UNPOLARIZED.
________________________________________________________________ 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.
15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown MAX221E
ABSOLUTE MAXIMUM RATINGS
VCC ..........................................................................-0.3V to +6V V+ ...............................................................(VCC - 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 (VCC + 0.3V) Output Voltages TOUT ................................................(V- - 0.3V) to (V+ + 0.3V) ROUT, INVALID ......................................-0.3V to (VCC + 0.3V) Short-Circuit Duration, TOUT .....................................Continuous Continuous Power Dissipation (TA = +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
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 = +5V 10%, C1-C4 = 0.1F, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER DC CHARACTERISTICS VCC Supply Current Shutdown Supply Current AutoShutdown Supply Current LOGIC INPUTS Input Leakage Current Input Threshold Low Input Threshold High Output Voltage Low Output Voltage High Output Leakage Current AUTOSHUTDOWN Receiver Input Threshold, Transmitter Enabled Receiver Input Threshold, Transmitter Disabled INVALID Output Voltage Low INVALID Output Voltage High Receiver Threshold to Transmitter Enabled Receiver Positive or Negative Threshold to INVALID High Receiver Positive or Negative Threshold to INVALID Low tWU tINVH tINVL Figure 3 ICC = 1A, Figure 3 ISINK = 1.6mA ISOURCE = 1.0mA Figure 3 Figure 3 Figure 3 VCC - 0.6 250 1 30 Positive threshold Negative threshold -2.7 -0.3 0.3 0.4 2.7 V V V V s s s VIL VIH VOL VOH TIN = 0 to VCC TIN, EN, FORCEOFF, FORCEON EN, FORCEOFF, TIN ROUT; ISINK = 3.2mA ROUT; ISOURCE = 1.0mA EN = VCC, 0 ROUT VCC 3.5 0.05 10 2.4 0.4 1 0.8 A V V V V A ICC ISHDN IAS No load, TA = +25C TA = +25C, Figure 1 5 1 1 10 10 10 mA A A SYMBOL CONDITIONS MIN TYP MAX UNITS
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5V 10%, C1-C4 = 0.1F, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER RECEIVER INPUT Input Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance TRANSMITTER OUTPUT Output Voltage Swing Output Resistance Output Short-Circuit Current ESD PROTECTION IEC 1000-4-2 Air-Gap Discharge RIN, TOUT IEC 1000-4-2 Contact Discharge Human Body Model 15 8 15 kV Driver loaded with 3k to ground VCC = V+ = V- = 0, VOUT = 2V 5 300 10 60 9 V mA TA = +25C, VCC = 5V TA = +25C, VCC = 5V VCC = 5V, no hysteresis in shutdown TA = +25C, VCC = 5V 3 -25 0.8 1.2 1.7 0.5 5 7 2.4 25 V V V V k SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX221E
TIMING CHARACTERISTICS
(VCC = +5V 10%, C1-C4 = 0.1F, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Maximum Data Rate Receiver Propagation Delay Receiver Output Enable Time Receiver Output Disable Time Transmitter Skew Receiver Skew Transition-Region Slew Rate | tPHL tPLH | TA = +25C, VCC = 5V, RL = 3k to 7k, CL = 500pF to 1000pF, measured from -3V to +3V or +3V to -3V 3 tPHL, tPLH SYMBOL CONDITIONS RL = 3k to 7k, CL = 50pF to 1000pF, VCC = 4.5V CL = 150pF Normal operation Normal operation | tPHL tPLH | (Note 1) MIN 250 0.15 300 200 200 50 6 30 TYP MAX UNITS kbps ms ns ns ns ns V/s
Note 1: Transmitter skew is measured at the transmitter zero crosspoints.
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown MAX221E
Typical Operating Characteristics
(VCC = +5V, 250kbps data rate, 0.1F capacitors, transmitter loaded with 3k and CL, TA = +25C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX221Etoc01
SLEW RATE vs. LOAD CAPACITANCE
MAX221Etoc02
OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE
MAX221Etoc03
10 TRANSMITTER OUTPUT VOLTAGE (V) 8 6 4 2 0 -2 -4 -6 -8 -10 0 1000 2000 3000 4000 20kbps 120kbps 250kbps 20kbps 120kbps 250kbps
50
50
40 SLEW RATE (V/s) +SLEW 30
40 SUPPLY CURRENT (mA) 250kbps 30
20
-SLEW
20
10
10 120kbps 20kbps 2000 3000 4000 5000
0 5000 0 1000 2000 3000 4000 5000 LOAD CAPACITANCE (pF) LOAD CAPACITANCE (pF)
0 0 1000 LOAD CAPACITANCE (pF)
Pin Description
PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 NAME EN C1+ V+ C1C2+ C2VRIN ROUT INVALID TIN FORCEON TOUT GND VCC FORCEOFF FUNCTION Receiver Enable Control. Drive low for normal operation. Drive high to force the receiver output (ROUT) into a high-impedance state. Positive Terminal of the Voltage Doubler Charge-Pump Capacitor Positive Voltage Generated by the Charge Pump Negative Terminal of the Voltage Doubler 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, 15kV ESD protected TTL/CMOS Receiver Output Output of the Invalid Signal Detector. INVALID is pulled low if no valid RS-232 level is present on the receiver input. TTL/CMOS Transmitter Input Drive high to override automatic circuitry, keeping transmitter and charge pump on. FORCEOFF must be high (Table 1). RS-232 Transmitter Output, 15kV ESD Protected Ground +4.5V to +5.5V Supply Voltage 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).
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown
RS-232 Receiver
+5V CBYPASS 0.1F C1 0.1F ISHDN 15 2 C1+ 4 C15 C2 0.1F 6 C2+ C2TOUT 13 3k 9 ROUT 5k RIN 8 VCC V+ 3 C3 0.1F
MAX221E
MAX221E
V-
7 C4 0.1F
11 TIN
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 connected 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 operating 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 connected 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 VCC, V- is pulled to ground, and the transmitter output is high impedance. The time required to exit shutdown is typically 100s (Figure 3b).
1
EN FORCEON GND 14
INVALID
10
TO POWERMANAGEMENT UNIT
12
FORCEOFF
16
Figure 1. Shutdown Current Test Circuit
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX221E's internal power supply consists of a dual charge pump that provides a positive output voltage (doubling charge pump) and negative output voltage (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 Vsupplies.
RS-232 Transmitter
The transmitter is an inverting level translator that converts 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 transmitter input does not have a pull-up resistor.
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown MAX221E
Table 1. Output Control Truth Table
OPERATION STATUS FORCEON FORCEOFF EN VALID RECEIVER TOUT ROUT
Shutdown (Forced Off) Normal Operation (Forced On) Normal Operation (AutoShutdown) Shutdown (AutoShutdown)
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 X X Yes Yes No No
High-Z High-Z Active Active Active Active High-Z High-Z
Active High-Z Active High-Z Active High-Z Active High-Z
x = Don't care
+0.3V TO MAX221E POWER SUPPLY AND TRANSMITTER INVALID
FORCEOFF FORCEON INVALID
POWER DOWN
RIN
-0.3V
30s COUNTER R
INVALID IS AN INTERNALLY GENERATED SIGNAL USED BY AUTOSHUTDOWN LOGIC AND APPEARS AS AN OUTPUT. * TRANSMITTER IS DISABLED, REDUCING SUPPLY CURRENT TO 1A IF RECEIVER INPUT IS BETWEEN +0.3V AND -0.3V FOR AT LEAST 30s. POWER DOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTER AND POWER SUPPLIES.
Figure 2a. Entering 1A Supply Mode via AutoShutdown
Figure 2c. AutoShutdown Logic
+2.7V TO MAX221E POWER SUPPLY INVALID
RIN
-2.7V
30s COUNTER R
Table 2. INVALID Truth Table
RS-232 SIGNAL PRESENT AT RECEIVER INPUT Yes No INVALID OUTPUT High Low
* 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 30s.
Figure 2b. Transmitter Enabled Using AutoShutdown
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown
Software-Controlled Shutdown
TRANSMITTER ENABLED, INVALID HIGH RECEIVER INPUT LEVEL +2.7V INDETERMINATE +0.3V 0 -0.3V INDETERMINATE -2.7V TRANSMITTER ENABLED, INVALID HIGH AUTOSHUTDOWN, TRANSMITTER DISABLED, 1A SUPPLY CURRENT, INVALID LOW
MAX221E
For direct software control, use INVALID to indicate a DTR or Ring Indicator signal. Connect FORCEOFF and FORCEON together to disable AutoShutdown so the line acts like a SHDN input.
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 output and receiver input of the MAX221E 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 output and receiver input of the MAX221E are characterized for protection to the following limits: 1) 15kV using the Human Body Model 2) 8kV using the Contact-Discharge Method specified in IEC 1000-4-2
a)
RECEIVER INPUT VOLTAGE (V)
INVALID REGION
VCC INVALID OUTPUT (V) 0
tINVL
tINVH tWU
3) 15kV using IEC 1000-4-2's Air-Gap Method
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.
V+ VCC 0 V-
Human Body Model
Figure 5a shows the Human Body Model, and Figure 5b 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 1.5k resistor.
0.1F 1M
b)
Figure 3. AutoShutdown Trip Levels
POWERMANAGEMENT UNIT
MASTER SHDN LINE
IEC 1000-4-2
The IEC 1000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The MAX221E helps you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without the need for additional ESD-protection components. The major difference between tests done using the Human Body Model and IEC 1000-4-2 (Figure 6) is higher peak current in the IEC 1000-4-2 because series resistance is lower in the IEC 1000-4-2 model. Hence,
FORCEOFF FORCEON
MAX221E
Figure 4. AutoShutdown with Initial Turn-On to Wake Up a Mouse or Another System
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown MAX221E
RC 50M to 100M CHARGE-CURRENT LIMIT RESISTOR DEVICE UNDER TEST HIGHVOLTAGE DC SOURCE RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
RC 1M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1500 DISCHARGE RESISTANCE
Cs 100pF
STORAGE CAPACITOR
Cs 150pF
STORAGE CAPACITOR
Figure 5a. Human Body ESD Test Model
Figure 6a. IEC 1000-4-2 ESD Test Model
I 100% IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME tDL CURRENT WAVEFORM 10% t r = 0.7ns to 1ns t 60ns Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) I PEAK 90%
30ns
Figure 5b. Human Body Model Current Waveform
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
the ESD that withstands voltage measured to IEC 10004-2 is generally lower than that measured using the Human Body Model. Figure 6a shows the IEEE 1000-42 model and Figure 6b shows the current waveform for the 8kV IEC 1000-4-2 Level 4 ESD Contact-Discharge test. The Air-Gap Method involves approaching the device with a charged probe. The Contact-Discharge Method connects the probe to the device before the probe is energized.
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 not only by RS-232 inputs and outputs, but also by contact that occurs due to handling and assembling during manufacturing. Therefore, after PC board assembly, the Machine Model is less relevant to I/O ports.
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown
__________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 part for activity. nominal value. The capacitor's equivalent series resistance (ESR) usually rises at low temperatures and influences the amount of ripple on V+ and V-.
MAX221E
Power-Supply Decoupling
In most circumstances, a 0.1F 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.
Capacitor Selection
The capacitor type used for C1-C4 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 0.1F 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). When using the minimum 0.1F capacitors, make sure the capacitance does not degrade excessively with temperature. If in doubt, use capacitors with a larger
Transmitter Output when Exiting Shutdown
Figure 7 shows the transmitter output when exiting shutdown mode. The transmitter is loaded with 3k in parallel with 1000pF. 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 5.0V minimum transmitter output voltage even at high data rates. Figure 8 shows a transmitter loopback test circuit. Figure 9 shows the loopback test result at 120kbps, and Figure 10 shows the same test at 250kbps.
+5V 5V/div TIN = GND FORCEON = FORCEOFF 0.1F C3 VCC
C1+ C1 C15V/div TOUT C2 C2TIN = VCC TIN ROUT 50s/div 0V EN FORCEOFF FORCEON C2+
V+
MAX221E
VC4
TOUT RIN 5k 1000pF
Figure 7. Transmitter Output when Exiting Shutdown or Powering Up
VCC
GND
INVALID
Figure 8. Loopback Test Circuit
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown MAX221E
5V/div TIN 5V/div TIN
5V/div
TOUT
5V/div
TOUT
5V/div
ROUT
5V/div
ROUT
2s/div
2s/div
Figure 9. Loopback Test Result at 120kbps
Figure 10. Loopback Test Result at 250kbps
___________________Chip Information
TRANSISTOR COUNT: 157
10
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15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown
Package Information
TSSOP.EPS
MAX221E
______________________________________________________________________________________
11
15kV ESD-Protected, +5V, 1A, Single RS-232 Transceiver with AutoShutdown MAX221E
Package Information (continued)
SSOP.EPS
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 Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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