19-1520; Rev 0; 8/99 +5V, 1µA, Single RS-232 Transceiver with AutoShutdown The MAX221 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 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 lowpower shutdown mode when the RS-232 cable is disconnected, 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 connected, signaling the host that a peripheral is connected to the communications port. 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 ESD protection, refer to the MAX221E data sheet. Features ♦ Single RS-232 Transceiver in a Small 16-Pin TSSOP Package ♦ 1µA Supply Current ♦ AutoShutdown Saves Power Without Changes to BIOS ♦ Guaranteed 250kbps Data Rate Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX221CUE 0°C to +70°C 16 TSSOP MAX221CAE MAX221EUE MAX221EAE 0°C to +70°C -40°C to +85°C -40°C to +85°C 16 SSOP 16 TSSOP 16 SSOP Applications Maintenance/Diagnostic Ports Industrial Systems Telecommunications Typical Operating Circuit Set-Top Boxes +5V Pin Configuration CBYPASS C1 0.1µF TOP VIEW 2 C1+ 4 C15 16 FORCEOFF EN 1 15 VCC C1+ 2 14 GND V+ 3 C1- 4 MAX221 C2 0.1µF 15 0.1µF 6 VCC 3 C3 0.1µF V+ MAX221 C2+ V- 7 C4 0.1µF C2- 11 TIN TOUT 13 13 TOUT C2+ 5 12 FORCEON C2- 6 11 TIN 9 ROUT RIN 8 5k 10 INVALID V- 7 9 RIN 8 ROUT TSSOP/SSOP 1 12 EN FORCEON INVALID GND FORCEOFF 10 16 TO POWERMANAGEMENT UNIT VCC 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. MAX221 General Description MAX221 +5V, 1µA, Single RS-232 Transceiver with AutoShutdown 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 = +70°C) 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 MAX221E_ _ ..................................................-40°C to +85°C Maximum Junction Temperature ................................... +150°C Storage Temperature Range ........................... -65°C to +150°C Lead Temperature (soldering, 10sec) ............................ +300°C 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 = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC CHARACTERISTICS VCC Supply Current Shutdown Supply Current AutoShutdown Supply Current ICC No load, TA = +25°C 5 10 mA ISHDN TA = +25°C, Figure 1 1 10 µA 1 10 µA IAS LOGIC INPUTS Input Leakage Current IIN TIN = 0 to VCC ±1 µA Input Threshold Low VIL TIN; EN, FORCEOFF, FORCEON 0.8 V Input Threshold High VIH TIN, EN, FORCEOFF Output Voltage Low VOL ROUT; ISINK = 3.2mA Output Voltage High VOH ROUT; ISOURCE = 1.0mA 2.4 3.5 EN = VCC, 0 ≤ ROUT ≤ VCC Output Leakage Current V 0.4 V V ±0.05 ±10 µA AUTOSHUTDOWN Receiver Input Threshold, Transmitter Enabled Figure 3 Receiver Input Threshold, Transmitter Disabled ICC = 1µA, Figure 3 INVALID Output Voltage Low ISINK = 1.6mA INVALID Output Voltage High ISOURCE = 1.0mA Receiver Threshold to Transmitter Enabled 2.7 Positive threshold Negative threshold -2.7 -0.3 VCC - 0.6 V 0.3 V 0.4 V V tWU Figure 3 250 µs Receiver Positive or Negative Threshold to INVALID High tINVH Figure 3 1 µs Receiver Positive or Negative Threshold to INVALID Low tINVL Figure 3 30 µs 2 _______________________________________________________________________________________ +5V, 1µA, Single RS-232 Transceiver with AutoShutdown (VCC = +5V ±10%, C1–C4 = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 25 V 2.4 V 7 kΩ RECEIVER INPUT Input Voltage Range -25 Input Threshold Low TA = +25°C, VCC = 5V Input Threshold High TA = +25°C, VCC = 5V Input Hysteresis VCC = 5V, no hysteresis in shutdown Input Resistance TA = +25°C, VCC = 5V 0.8 1.2 1.7 V 0.5 3 5 ±9 V TRANSMITTER OUTPUT Output Voltage Swing Driver loaded with 3kΩ to ground ±5 Output Resistance VCC = V+ = V- = 0, VOUT = ±2V 300 Output Short-Circuit Current V Ω ±10 ±60 mA MAX UNITS TIMING CHARACTERISTICS (VCC = +5V ±10%, C1–C4 = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS RL = 3kΩ to 7kΩ, CL = 50pF to 1000pF, VCC = 4.5V Maximum Data Rate MIN TYP 250 kbps CL = 150pF 0.15 µs Receiver Output Enable Time Normal operation 300 ns Receiver Output Disable Time Normal operation 200 ns (Note 1) 200 ns 50 ns Receiver Propagation Delay Transmitter Skew tPHL, tPLH | tPHL - tPLH | | tPHL - tPLH | Receiver Skew Transition-Region Slew Rate TA = +25°C, VCC = 5V, RL = 3kΩ to 7kΩ, CL = 500pF to 1000pF, measured from -3V to +3V or +3V to -3V 3 6 30 V/µs Note 1: Transmitter skew is measured at the transmitter zero crosspoints. _______________________________________________________________________________________ 3 MAX221 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = +5V, 250kbps data rate, 0.1µF capacitors, transmitter loaded with 3kΩ and CL, TA = +25°C, unless otherwise noted.) SLEW RATE vs. LOAD CAPACITANCE 8 40 120kbps 250kbps 2 0 250kbps -2 -4 20kbps -6 40 SUPPLY CURRENT (mA) 20kbps 4 SLEW RATE (V/µs) 6 50 MAX221-02 50 MAX221-01 10 OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE MAX221-03 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE TRANSMITTER OUTPUT VOLTAGE (V) MAX221 +5V, 1µA, Single RS-232 Transceiver with AutoShutdown +SLEW 30 -SLEW 20 120kbps 250kbps 30 20 10 10 0 0 -8 120kbps -10 0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000 0 LOAD CAPACITANCE (pF) LOAD CAPACITANCE (pF) 1000 2000 20kbps 3000 4000 5000 LOAD CAPACITANCE (pF) Pin Description 4 PIN NAME FUNCTION 1 EN 2 C1+ 3 V+ Positive Voltage Generated by the Charge Pump 4 C1- Negative Terminal of the Voltage Doubler Charge-Pump Capacitor 5 C2+ Positive Terminal of the Inverting Charge-Pump Capacitor 6 C2- Negative Terminal of the Inverting Charge-Pump Capacitor 7 V- 8 RIN 9 ROUT 10 INVALID 11 TIN 12 FORCEON 13 TOUT RS-232 Transmitter Output 14 GND Ground 15 VCC +4.5V to +5.5V Supply Voltage 16 FORCEOFF 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 Negative Voltage Generated by the Charge Pump RS-232 Receiver Input 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). 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). _______________________________________________________________________________________ +5V, 1µA, Single RS-232 Transceiver with AutoShutdown CBYPASS C1 0.1µF ISHDN 2 C1+ 4 C15 C2 0.1µF 15 0.1µF 6 C3 0.1µF VCC 3 V+ MAX221 C2+ V- 7 C4 0.1µF C2- 11 TIN TOUT 13 3k RIN 8 9 ROUT 5k 1 12 EN FORCEON INVALID GND FORCEOFF 10 TO POWERMANAGEMENT UNIT 16 14 Figure 1. Shutdown Current Test Circuit _______________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 (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 3kΩ 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. RS-232 Receiver The MAX221’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 MAX221 is in shutdown (FORCEOFF = low). 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). AutoShutdown The MAX221 achieves 1µA 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 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. Table 1 and Figure 2c summarize the MAX221 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 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 RS232 ports on both systems remain enabled. When shut down, the device’s charge pumps are 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 100µs (Figure 3b). Software-Controlled Shutdown 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. _______________________________________________________________________________________ 5 MAX221 +5V MAX221 +5V, 1µA, Single RS-232 Transceiver with AutoShutdown Table 1. Output Control Truth Table OPERATION STATUS Shutdown (Forced Off) Normal Operation (Forced On) Normal Operation (AutoShutdown) Shutdown (AutoShutdown) FORCEON FORCEOFF EN VALID RECEIVER LEVEL TOUT ROUT X 0 0 X High-Z Active X 0 1 X High-Z High-Z 1 1 0 X Active Active 1 1 1 X Active High-Z 0 1 0 Yes Active Active 0 1 1 Yes Active High-Z 0 1 0 No High-Z Active 0 1 1 No High-Z High-Z X = Don’t care FORCEOFF +0.3V RIN -0.3V 30µs COUNTER R TO MAX221 POWER SUPPLY AND TRANSMITTER POWER DOWN FORCEON INVALID INVALID 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. Figure 2a. Entering 1µA Supply Mode via AutoShutdown POWER DOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTER AND POWER SUPPLIES. Figure 2c. AutoShutdown Logic Table 2. INVALID Truth Table +2.7V RIN -2.7V 30µs COUNTER R TO MAX221 POWER SUPPLY INVALID RS-232 SIGNAL PRESENT AT RECEIVER INPUT INVALID OUTPUT Yes High No 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 30µs. Figure 2b. Transmitter Enabled Using AutoShutdown 6 _______________________________________________________________________________________ +5V, 1µA, Single RS-232 Transceiver with AutoShutdown 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. RECEIVER INPUT LEVEL TRANSMITTER ENABLED, INVALID HIGH +2.7V INDETERMINATE +0.3V 0 AUTOSHUTDOWN, TRANSMITTER DISABLED, 1µA SUPPLY CURRENT, INVALID LOW Capacitor Selection -0.3V INDETERMINATE -2.7V TRANSMITTER ENABLED, INVALID HIGH a) RECEIVER INPUT VOLTAGE (V) INVALID REGION VCC INVALID OUTPUT (V) 0 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 resistance (ESR) usually rises at low temperatures and influences the amount of ripple on V+ and V-. tINVL tINVH tWU V+ VCC 0 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. Transmitter Output when Exiting Shutdown b) Figure 3. AutoShutdown Trip Levels POWERMANAGEMENT UNIT 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 0.1µF 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). MASTER SHDN LINE 0.1µF 1MΩ Figure 5 shows the transmitter output when exiting shutdown mode. The transmitter is loaded with 3kΩ in parallel 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. High Data Rates FORCEOFF FORCEON MAX221 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. Figure 4. AutoShutdown with Initial Turn-On to Wake Up a Mouse or Another System _______________________________________________________________________________________ 7 MAX221 Applications Information MAX221 +5V, 1µA, Single RS-232 Transceiver with AutoShutdown 5V/div TIN = GND 5V/div FORCEON = FORCEOFF 5V/div TIN TOUT 5V/div TOUT 5V/div ROUT TIN = VCC 2µs/div 50µs/div Figure 5. Transmitter Output Exiting Shutdown or Powering Up Figure 7. Loopback Test Result at 120kbps +5V 0.1µF 5V/div TIN 5V/div TOUT 5V/div ROUT C3 C1+ VCC V+ C1 C1C2+ MAX221 VC4 C2 C2TOUT TIN RIN ROUT 0V EN 2µs/div Figure 8. Loopback Test Result at 250kbps 5k 1000pF VCC FORCEOFF FORCEON GND INVALID ___________________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.