19-0246; Rev 1; 7/95 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver ________________________Applications Battery-Powered Equipment Computers Printers Peripherals Instruments Modems ON/OFF 6 3 1 LX SHDN T1 8 T2IN T2 9 R1OUT R1 10 R2OUT R2 EN ENABLE 4 ♦ 120kbps Data Rate ♦ Low-Cost Surface-Mount Components ♦ Meets EIA/TIA-232E Specifications ♦ 1µA Low-Power Shutdown Mode ♦ Both Receivers Active During Low-Power Shutdown ♦ Three-State Receiver Outputs ♦ Flow-Through Pinout ♦ On-Board DC-DC Converters ♦ 20-Pin SSOP, Wide SO, or DIP Packages ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX218CPP 0°C to +70°C 20 Plastic DIP MAX218CWP 0°C to +70°C 20 Wide SO MAX218CAP MAX218C/D MAX218EPP 0°C to +70°C 0°C to +70°C -40°C to +85°C 20 SSOP Dice* 20 Plastic DIP MAX218EWP MAX218EAP -40°C to +85°C -40°C to +85°C 20 Wide SO 20 SSOP __________________Pin Configuration 15 20 GND N.C. 2 19 V+ C1+ 18 SHDN 3 18 C1+ 16 EN 4 17 GND T1OUT 14 GND 5 C1- 7 T1IN ♦ +1.8V to +4.25V Supply Voltage Range LX 1 V- MAX218 ♦ Operates Directly from Two Alkaline, NiCd, or NiMH Cells TOP VIEW 19 V+ VCC BETTER THAN BIPOLAR! *Contact factory for dice specifications. __________Typical Operating Circuit 1.8V TO 4.25V ____________________________Features MAX218 16 C1- VCC 6 15 V- T2OUT 13 T1IN 7 14 T1OUT R1IN 12 T2IN 8 13 T2OUT R2IN 11 GND 5, 17, 20 R1OUT 9 12 R1IN R2OUT 10 11 R2IN DIP/SO/SSOP ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX218 _______________General Description The MAX218 RS-232 transceiver is intended for batterypowered EIA/TIA-232E and V.28/V.24 communications interfaces that need two drivers and two receivers with minimum power consumption. It provides a wide +1.8V to +4.25V operating voltage range while maintaining true RS-232 and EIA/TIA-562 voltage levels. The MAX218 runs from two alkaline, NiCd, or NiMH cells without any form of voltage regulator. A shutdown mode reduces current consumption to 1µA, extending battery life in portable systems. While shut down, all receivers can remain active or can be disabled under logic control, permitting a system incorporating the CMOS MAX218 to monitor external devices while in low-power shutdown mode. A guaranteed 120kbps data rate provides compatibility with popular software for communicating with personal computers. Three-state drivers are provided on all receiver outputs so that multiple receivers, generally of different interface standards, can be wire-ORed at the UART. The MAX218 is available in 20-pin DIP, SO, and SSOP packages. MAX218 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver ABSOLUTE MAXIMUM RATINGS Supply Voltages VCC ....................................................................-0.3V to +4.6V V+ .......................................................... (VCC - 0.3V) to +7.5V V- .......................................................................+0.3V to -7.4V VCC to V- ..........................................................................+12V LX ................................................................-0.3V to (1V + V+) Input Voltages ———– T_IN, EN, SHDN ................................................. -0.3V to +7V R_IN .................................................................................±25V Output Voltages T_OUT.............................................................................±15V) R_OUT ....................................................-0.3V to (VCC + 0.3V) Short-Circuit Duration, R_OUT, T_OUT to GND ....... Continuous Continuous Power Dissipation (TA = +70°C) Plastic DIP (derate 11.11mW/°C above +70°C) ..........889mW Wide SO (derate 10.00mW/°C above +70°C)..............800mW SSOP (derate 8.00mW/°C above +70°C) ...................640mW Operating Temperature Ranges MAX218C_ P ..................................................... 0°C to +70°C MAX218E_ P ................................................... -40°C to +85°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 (Circuit of Figure 1, VCC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.0V, TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS DC CHARACTERISTICS Operating Voltage Range Supply Current (Note 1) Shutdown Supply Current 1.8 ———– No load, VCC = EN = SHDN = 3.0V, TA = +25°C ———– SHDN = EN = 0V, all R_INs static ———– SHDN = 0V, EN = VCC, all R_INs static 4.25 V 1.9 3.0 mA 0.04 10 0.04 10 µA LOGIC Input Logic Threshold High ———– T_IN, EN, SHDN ———– T_IN, EN, SHDN Input Hysteresis T_IN Input Leakage Current ———– T_IN, EN, SHDN = 0V or VCC Output Voltage Low R_OUT, IOUT = 1.0mA Output Voltage High R_OUT, IOUT = -0.4mA Output Leakage Current R_OUT, 0V ≤ R_OUT ≤ VCC, EN = 0V Input Logic Threshold Low 0.33 x VCC 0.67 x VCC V 0.1 0.001 VCC - 0.25 V V ±1 µA 0.4 V ±10 µA +25 V VCC - 0.08 0.05 V EIA/TIA-232E RECEIVER INPUTS Input Voltage Range Input Threshold Low Input Threshold High -25 VCC = 2.0V to 4.25V 0.4 VCC = 1.8V to 4.25V 0.3 VCC = 1.8V to 4.25V 3.0 VCC = 1.8V to 3.6V 2.8 Input Hysteresis Input Resistance V 0.7 -15V < R_IN < +15V 3 5 ±6 V V 7 kΩ EIA/TIA-232E TRANSMITTER OUTPUTS Output Voltage Swing All transmitter outputs loaded with 3kΩ to ground ±5 Output Resistance VCC = 0V, -2V < T_OUT < +2V 300 Output Short-Circuit Current ±24 Note 1: Entire supply current for the circuit of Figure 1. 2 V Ω _______________________________________________________________________________________ ±100 mA 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver (Circuit of Figure 1, VCC = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.0V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN 1000pF || 3kΩ load each transmitter, 150pF load each receiver Data Rate TYP MAX 120 UNITS kbps Receiver Output Enable Time tER 90 300 ns Receiver Output Disable Time tDR 200 500 ns Transmitter Output Enable Time tET 140 450 µs Transmitter Output Disable Time tDT 500 Receiver Propagation Delay Transmitter Propagation Delay Transition Region Slew Rate ns tPHLR 150pF load 290 700 tPLHR 150pF load 260 700 tPHLT 2500pF || 3kΩ load 1.9 2.7 tPLHT 2500pF || 3kΩ load 1.8 2.7 TA = +25°C, VCC = 3.0V, RL = 3kΩ to 7kΩ, CL = 50pF to 2500pF, measured from +3V to -3V or -3V to +3V 3.0 30 ns µs V/µs ______________________________________________________________Pin Description PIN NAME FUNCTION 1 LX 2 N.C. 3 ———– SHDN Shutdown Control. Connect to VCC for normal operation. Connect to GND to shut down the power supply and to disable the drivers. Receiver status is not changed by this control. 4 EN Receiver Output Enable Control. Connect to VCC for normal operation. Connect to GND to force the receiver outputs into high-Z state. 5, 17, 20 GND Ground. Connect all GND pins to ground. 6 VCC Supply Voltage Input; 1.8V to 4.25V. Bypass to GND with at least 1µF. See Capacitor Selection section. 7, 8 T1IN, T2IN 9, 10 R1OUT, R2OUT 11, 12 R2IN, R1IN 13, 14 T2OUT, T1OUT 15 V- 16, 18 C1-, C1+ 19 V+ Inductor/Diode Connection Point Not internally connected Transmitter Inputs Receiver Outputs; swing between GND and VCC. Receiver Inputs Transmitter Outputs; swing between V+ and V-. Negative Supply generated on-board Terminals for Negative Charge-Pump Capacitor Positive Supply generated on-board _______________________________________________________________________________________ 3 MAX218 TIMING CHARACTERISTICS __________________________________________Typical Operating Characteristics (Circuit of Figure 1, VCC = 1.8V, all transmitter outputs loaded with 3kΩ, TA = +25°C, unless otherwise noted.) TRANSMITTING SUPPLY CURRENT vs. LOAD CAPACITANCE SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT (mA) VCC = 2.4V 90 100 240kbps 80 60 120kbps 40 20kbps 20 0kbps MAX3218-02 120 100 SUPPLY CURRENT (mA) 1 TRANSMITTER FULL DATA RATE 1 TRANSMITTER 1/8 DATA RATE RL = 3kΩ + 2500pF MAX3218-01 140 80 235kbps TRANSMITTER 1 OPERATING AT SPECIFIED BIT RATE, TRANSMITTER 2 OPERATING AT 1/16 THAT RATE. 70 60 120kbps 50 40 20kbps 30 20 0 1.8 2.4 3.0 3.6 1000 0 4.2 2000 3000 4000 5000 LOAD CAPACITANCE (pF) SUPPLY VOLTAGE (V) TIME TO EXIT SHUTDOWN (ONE TRANSMITTER HIGH, ONE TRANSMITTER LOW) SHDN VOH 2V/div T_OUT VCC = 1.8V RL = 3kΩ || 2500pF VOL 100µs/div SLEW RATE vs. TRANSMITTER CAPACITANCE TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE AT 120kbps 10 VOUT+ SLEW RATE (V/µs) 4 2 0 -2 MAX3218-05 6 +SLEW 8 -SLEW 6 4 DATA RATE 120kbps, TRANSMITTERS LOADED WITH 3kΩ PLUS INDICATED CAPACITANCE -4 VOUT- 2 -6 0 -8 0 1000 2000 3000 4000 LOAD CAPACITANCE (pF) 4 12 MAX3218-04 8 TRANSMITTER OUTPUT VOLTAGE (V) MAX218 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver 5000 0 1000 2000 3000 4000 LOAD CAPACITANCE (pF) _______________________________________________________________________________________ 5000 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver 6 1µF C4 V+ LX V- VCC C1+ MAX218 ON/OFF 3 SHDN C1- 7 T1IN 16 1µF C3 0.47µF C1 R2IN 11 R2 EN GND 4 Switch-Mode Power Supply The switch-mode power supply uses a single inductor with one diode and three small capacitors to generate ±6.5V from an input voltage in the 1.8V to 4.25V range. R1IN 12 R1 10 R2OUT 18 T2OUT 13 T2 9 R1OUT 15 T1OUT 14 T1 8 T2IN ENABLE 1µF C2 19 1 1.8V TO 4.25V The transmitters and receivers are guaranteed to operate at 120kbps data rates, providing compatibility with LapLink™ and other high-speed communications software. A shutdown mode extends battery life by reducing supply current to 0.04µA. While shut down, all receivers can either remain active or be disabled under logic control. With this feature, the MAX218 can be in low-power shutdown mode and still monitor activity on external devices. Three-state drivers are provided on both receiver outputs. Inductor Selection Use a 15µH inductor with a saturation current rating of at least 350mA and less than 1Ω resistance. Table 1 lists suppliers of inductors that meet the 15µH/350mA/1Ω specifications. 5, 17, 20 Figure 1. Single-Supply Operation _______________Detailed Description The MAX218 line driver/receiver is intended for batterypowered EIA/TIA-232 and V.28/V.24 communications interfaces that require two drivers and two receivers. The operating voltage extends from 1.8V to 4.25V, yet the device maintains true RS-232 and EIA/TIA-562 transmitter output voltage levels. This wide supply voltage range permits direct operation from a variety of batteries without the need for a voltage regulator. For example, the MAX218 can be run directly from a single lithium cell or a pair of alkaline cells. It can also be run directly from two NiCd or NiMH cells from full-charge voltage down to the normal 0.9V/cell end-of-life point. The 4.25V maximum supply voltage allows the two rechargeable cells to be trickle- or fast-charged while driving the MAX218. The circuit comprises three sections: power supply, transmitters, and receivers. The power-supply section converts the supplied input voltage to 6.5V, providing the voltages necessary for the drivers to meet true RS-232 levels. External components are small and inexpensive. Diode Selection Key diode specifications are fast recovery time (<10ns), average current rating (>100mA), and peak current rating (>350mA). Inexpensive fast silicon diodes, such as the 1N6050, are generally recommended. More expensive Schottky diodes improve efficiency and give slightly better performance at very low VCC voltages. Table 1 lists suppliers of both surface-mount and through-hole diodes. 1N914s are usually satisfactory, but specifications and performance vary widely with different manufacturers. Capacitor Selection Use capacitors with values at least as indicated in Figure 1. Capacitor C2 determines the ripple on V+, but not the absolute voltage. Capacitors C1 and C3 determine both the ripple and the absolute voltage of V-. Bypass VCC to GND with at least 1µF (C4) placed close to pins 5 and 6. If the VCC line is not bypassed elsewhere (e.g., at the power supply), increase C4 to 4.7µF. You may use ceramic or polarized capacitors in all locations. If you use polarized capacitors, tantalum types are preferred because of the high operating frequency of the power supplies (about 250kHz). If aluminum electrolytics are used, higher capacitance values may be required. ™ LapLink is a trademark of Traveling Software, Inc. _______________________________________________________________________________________ 5 MAX218 D1 1N6050 15µH MAX218 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver Table 1. Suggested Component Suppliers MANUFACTURER PART NUMBER PHONE FAX Inductors—Surface Mount Murata-Erie LQH4N150K-TA USA (404) 436-1300 Japan (075) 951-9111 USA (404) 436-3030 Japan (075) 955-6526 Sumida CD43150 USA (708) 956-0666 Japan (03) 3607-5111 USA (708) 956-0702 Japan (03) 3607-5428 TDK NLC453232T-150K USA (708) 803-6100 Japan (03) 3278-5111 USA (708) 803-6296 Japan (03) 3278-5358 Central Semiconductor CMPSH-3, Schottky USA (516) 435-1110 USA (516) 435-1824 Motorola MMBD6050LT1, Silicon USA (408) 749-0510 USA (408) 991-7420 Philips PMBD6050, Silicon USA (401) 762-3800 USA (401) 767-4493 1N6050, Silicon 1N5817, Schottky USA (408) 749-0510 USA (408) 991-7420 Diodes—Surface Mount Diodes—Through-Hole Motorola RS-232 Drivers The two drivers are identical, and deliver EIA/TIA-232E and EIA/TIA-562 output voltage levels when V DD is between 1.8V and 4.25V. The transmitters drive up to 3kΩ in parallel with 1000pF at up to 120kbps. Connect unused driver inputs to– either GND or VCC. Disable the ——— drivers by taking SHDN low. The transmitter outputs are ——— – forced into a high-impedance state when SHDN is low. RS-232 Receivers The two receivers are identical, and accept both EIA/TIA-232E and EIA/TIA-562 input signals. The CMOS receiver outputs swing rail-to-rail. When EN is high, ———–the receivers are active regardless of the state of SHDN. When EN is low, the receiver outputs are put into a high-impedance state. This allows two RS-232 ports (or two ports of different types) to be wired-ORed at the UART. Operating Modes ———– SHDN and EN determine the MAX218’s mode of operation, as shown in Table 2. Table 2. Operating Modes –———– RECEIVER DRIVER DC-DC SUPPLY SHDN EN OUTPUT OUTPUT CONVERTER CURRENT 6 L L High-Z High-Z OFF Minimum L H Enabled High-Z OFF Minimum H L High-Z Enabled ON Normal H H Enabled Enabled ON Normal Shutdown ———– When SHDN is low, the power supplies are disabled and the transmitters are put into a high-impedance ———–state. Receiver operation is not affected by taking SHDN low. Power consumption is dramatically reduced in shutdown mode. Supply current is minimized when the receiver inputs are static in any of three states: floating (ground), GND, or VCC. __________Applications Information Operation from Regulated/Unregulated Dual System Power Supplies The MAX218 is intended for use with three different power-supply sources: it can be powered directly from a battery, from a 3.0V or 3.3V power supply, or simultaneously from both. Figure 1 shows the single-supply configuration. Figure 2 shows the circuit for operation from both a 3V supply and a raw battery supply—an ideal configuration where a regulated 3V supply is being derived from two cells. In this application, the MAX218’s logic levels remain appropriate for interface with 3V logic, yet most of the power for the MAX218 is drawn directly from the battery, without suffering the efficiency losses of the DC-DC converter. This prolongs battery life. Bypass the input supplies with 0.1µF at VCC (C4) and at least 1µF at the inductor (C5). Increase C5 to 4.7µF if the power supply has no other bypass capacitor connected to it. _______________________________________________________________________________________ 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver 3V DC-DC CONVERTER MAX878 OR MAX756 OR MAX856 1µF C5 6 V- MAX218 3 SHDN C1+ C1- 7 T1IN R1 10 R2OUT R2 EN 4 18 16 1µF C3 0.47µF C1 T2OUT 13 T2 9 R1OUT 15 T1OUT 14 T1 8 T2IN ENABLE V+ VCC 0.1µF C4 ON/OFF 1µF C2 19 1 LX R1IN 12 R2IN 11 GND 5, 17, 20 Figure 2. Operating from Unregulated and Regulated Supplies Low-Power Operation The following suggestions will help you get maximum life out of your batteries. Shut the MAX218 down when it is not being used for transmission. The receivers can remain active when the MAX218 is shut down, to alert your system to external activity. Transmit at the highest practical data rate. Although this raises the supply current while transmission is in progress, the transmission will be over sooner. As long as the MAX218 is shut down as soon as each transmission ends, this practice will save energy. Operate your whole system from the raw battery voltage rather than suffer the losses of a regulator or DCDC converter. If this is not possible, but your system is powered from two cells and employs a 3V DC-DC converter to generate the main logic supply, use the circuit of Figure 2. This circuit draws most of the MAX218’s power straight from the battery, but still provides logiclevel compatibility with the 3V logic. Keep communications cables short to minimize capacitive loading. Lowering the capacitive loading on the transmitter outputs reduces the MAX218’s power consumption. Using short, low-capacitance cable also helps transmission at the highest data rates. ———– Keep the SHDN pin low — while ——–power is being applied to the MAX218, and take SH D N high only after VCC has risen above about 1.5V. This avoids active operation at very low voltages, where currents of up to 150mA can be drawn. This is especially important with ——— – systems powered from rechargeable cells; if SHDN is high while the cells are being trickle charged from a deep discharge, the MAX218 could draw a significant amount of the charging current until the battery voltage rises above 1.5V. Pin Configuration Change The Pin Configuration shows pin 2 as N.C. (no connect). Early samples had a bypass capacitor for the internal reference connected to pin 2, which was labeled REF. This bypass capacitor proved to be unnecessary and the connection has been omitted. Pin 2 may now be connected to ground, left open, or bypassed to GND with a capacitor. EIA/TIA-232E and _____________EIA/TIA-562 Standards RS-232 circuits consume much of their power because the EIA/TIA-232E standard demands that the transmitters deliver at least 5V to receivers with impedances that can be as low as 3kΩ. For applications where power consumption is critical, the EIA/TIA-562 standard provides an alternative. EIA/TIA-562 transmitter output voltage levels need only reach ±3.7V, and because they have to drive the same 3kΩ receiver loads, the total power consumption is considerably reduced. Since the EIA/TIA-232E and EIA/TIA-562 receiver input voltage thresholds are the same, interoperability between EIA/TIA-232E and EIA/TIA-562 devices is guaranteed. Maxim’s MAX560 and MAX561 are EIA/TIA-562 transceivers that operate on a single supply from 3.0V to 3.6V, and the MAX562 transceiver operates from 2.7V to 5.25V while producing EIA/TIA-562 levels. _______________________________________________________________________________________ 7 MAX218 D1 1N6050 15µH MAX218 1.8V to 4.25V-Powered, True RS-232 Dual Transceiver ______3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim PART No. OF SUPPLY No. OF RECEIVERS VOLTAGE TRANSMITTERS/ ACTIVE IN (V) RECEIVERS SHUTDOWN GUARANTEED DATA RATE (kbps) EIT/TIA232 OR 562 MAX212 3.0 to 3.6 3/5 5 120 232 MAX3212 2.7 to 3.6 3/5 5 120 232 MAX218 FEATURES Drives mice AutoShutdown, complementary receiver, drives mice, transient detection Operates directly from a battery without a voltage regulator 1.8 to 4.25 2/2 2 120 232 MAX3218 1.8 to 4.25 2/2 2 120 232 Same as MAX218, but with AutoShutdown MAX560 3.0 to 3.6 4/5 2 120 562 Pin-compatible with MAX213 MAX561 3.0 to 3.6 4/5 0 120 562 Pin-compatible with MAX214 MAX562 2.7 to 5.25 3/5 5 230 562 Wide supply range MAX563 3.0 to 3.6 2/2 2 120 562 0.1µF capacitors MAX3222 3.0 to 5.5 2/2 2 120 232 0.1µF capacitors MAX3223 3.0 to 5.5 2/2 2 120 232 0.1µF capacitors MAX3232 3.0 to 5.5 2/2 2 120 232 Pin-compatible with MAX232 MAX3241 3.0 to 5.5 2/2 2 120 232 MAX3243 3.0 to 5.5 3/5 1 120 232 0.1µF capacitors, 2 complementary receivers, drives mice 0.1µF capacitors, AutoShutdown, complementary receivers, drives mice ___________________Chip Topography LX GND V+ SHDN C1+ EN GND C1V- 0.101" (2.565mm) GND V CC T1OUT T1IN T2OUT T2IN R1IN R2OUT R2IN R1OUT 0.122" (3.099mm) TRANSISTOR COUNT: 571 SUBSTRATE CONNECTED TO GND 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 © 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.