MAX3388EEUG

19-1845; Rev 1; 9/01 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones Features ♦ VL Pin for Compatibility with Mixed-Voltage Systems ♦ Additional I/O for Hot-Sync Applications ♦ ±15kV ESD Protection on Rx Inputs, Tx Outputs, LIN, and SWIN ♦ Low 300µA Supply Current ♦ Guaranteed 460kbps Data Rate ♦ 1µA Low-Power Shutdown ♦ Integrated Switch for Powering Remote Circuitry ♦ Flow-Through Pinout ♦ LOUT Active During Shutdown (MAX3389E) Applications Subnotebook/Palmtop Computers PDAs and PDA Cradles Cell Phone Data Cables Battery-Powered Equipment Hand-Held Equipment Peripherals Ordering Information PART Typical Operating Circuit +2.5V 24 CBYPASS 1 C1+ C1 0.1µF 3 4 C2 0.1µF 5 14 23 VCC SHDN VL V+ 2 MAX3388E MAX3389E V- 24 TSSOP MAX3388EEUG -40°C to +85°C 24 TSSOP MAX3389ECUG 0°C to +70°C 24 TSSOP MAX3389EEUG -40°C to +85°C 24 TSSOP Pin Configuration 6 C4 0.1µF C2- 7 T1IN TOP VIEW T1OUT 21 C1+ 1 20 9 T3IN T3OUT 19 VL 13 R1OUT RS-232 I/O V+ 2 23 VCC C1- 3 22 GND C2+ 4 C2- 5 17 T1IN 7 18 R1IN T2IN 8 17 R2IN 16 T3IN 9 16 LIN SWIN 15 SWOUT 11 14 VL R2OUT 12 13 R1OUT V- 6 20 T2OUT 19 T3OUT R2IN 10 LOUT 5kΩ LIN 30kΩ SHDN GND 22 C; 4. MAX3388E MAX3389E 18 VL 12 R2OUT = ±15kV ESD PROTECTION 21 T1OUT R1IN 5kΩ SWOUT 24 SHDN T2OUT 8 T2IN 11 PIN-PACKAGE 0°C to +70°C C3 0.1µF C1C2+ TEMP. RANGE MAX3388ECUG LOUT 10 15 SWIN TSSOP ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX3388E/MAX3389E General Description The MAX3388E/MAX3389E are 2.5V-powered EIA/TIA232 and V.28/V.24 communications interfaces with low power requirements, high data-rate capabilities, and enhanced electrostatic discharge (ESD) protection. The MAX3388E/MAX3389E have two receivers and three transmitters. All RS-232 inputs and outputs are protected to ±15kV using the IEC 1000-4-2 Air-Gap Discharge method, ±8kV using the IEC 1000-4-2 Contact Discharge method, and ±15kV using the Human Body Model. In addition to the traditional RS-232 I/O, these devices have dedicated logic-level I/O pins for additional device-todevice handshaking. During shutdown the logic-level I/O pins are active for the MAX3389E. An internal 62Ω switch is provided to switch power to external circuitry or modules. A proprietary low-dropout transmitter output stage enables RS-232 compatible performance from a +2.35V to +3.0V supply with a dual charge pump. The charge pump requires only four small 0.1µF capacitors for operation from a +2.5V supply. The MAX3388E/MAX3389E are capable of running at data rates up to 460kbps while maintaining RS-232-compatible output levels. The MAX3388E/MAX3389E have a unique VL pin that allows interoperation in mixed-logic voltage systems. Both input and output logic levels are pin programmable through the VL pin. The MAX3388E/MAX3389E are available in a space-saving TSSOP package. MAX3388E/MAX3389E 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones ABSOLUTE MAXIMUM RATINGS VCC to GND ..............................................................-0.3V to +6V VL to GND...................................................-0.3V to (VCC + 0.3V) V+ to GND ................................................................-0.3V to +7V V- to GND .................................................................+0.3V to -7V V+ +V-(Note 1) ............................................................... +13V Input Voltages T_IN, SHDN, LIN to GND.......................................-0.3V to +6V R_IN to GND .....................................................................±25V SWIN to GND...........................................-0.3V to (VCC + 0.3V) Output Voltages T_OUT to GND...............................................................±13.2V R_OUT, SWOUT, LOUT to GND ................-0.3V to (VL + 0.3V) Short-Circuit Duration T_OUT to GND........................Continuous Continuous Power Dissipation (TA = +70°C) 24-Pin TSSOP (derate 12.2mW/°C above +70°C) ........975mW Operating Temperature Ranges MAX338_ECUG ...................................................0°C to +70°C MAX338_EEUG.................................................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V. 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. DC ELECTRICAL CHARACTERISTICS (VCC = VL = +2.35V to +3.0V, C1–C4 = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +2.5V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 1 10 µA 0.3 1 mA 0.6 V DC CHARACTERISTICS (VCC = +2.5V, TA = +25°C) Shutdown Supply Current SHDN = GND, all inputs at GND Supply Current SHDN = VCC, no load LOGIC INPUTS (T_IN, SHDN) Input Logic Low VL = +2.5V Input Logic High VL = +2.5V 1.5 Transmitter Input Hysteresis V 0.4 Input Leakage Current V ±0.01 ±1 µA ±0.05 ±10 µA 0.4 V RECEIVER OUTPUTS Output Leakage Current R_OUT, SHDN = 0 Output Voltage Low IOUT = 1.6mA Output Voltage High IOUT = -1mA VL 0.6 VL 0.13 V RECEIVER INPUTS Input Voltage Range -25 Input Threshold Low TA = +25°C, VL = +2.5V Input Threshold High TA = +25°C, VL = +2.5V 0.6 1.8 Input Hysteresis Input Resistance +25 1.1 V 2.4 V 7 kΩ 0.7 TA = +25°C 3 5 V V TRANSMITTER OUTPUTS Output Voltage Swing All transmitter outputs loaded with 3kΩ to ground ±3.7 ±4.2 V Output Resistance VCC = 0, transmitter output = ±2V 300 10M Ω Output Short-Circuit Current VT_OUT = 0 2 _______________________________________________________________________________________ ±60 mA 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones (VCC = VL = +2.35V to +3.0V, C1–C4 = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +2.5V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP VT_OUT = ±12V, transmitters disabled, VCC = 0 or +2.5V Output Leakage Current MAX UNITS ±25 µA HANDSHAKING I/O (LIN, LOUT) Input Voltage Range 0 Input Threshold Low LIN, VL = +2.5V, TA = +25°C Input Threshold High LIN, VL = +2.5V, TA = +25°C 0.6 VCC 1.1 1.7 Input Hysteresis V V 2 V 40 kΩ 0.6 V Input Resistance TA = +25oC Output Voltage Low LOUT, ISINK = 1.6mA 0.4 V Output Leakage Current LOUT = VL, LIN = low or float ±10 µA VCC V 20 SWITCH (SWIN, SWOUT) Input Voltage Range 0 On-Resistance 62 SHDN = 0 Off-Leakage Current 100 Ω ±1 µA Turn-On Time 0.18 µs Turn-Off Time 0.7 µs ESD PROTECTION R_IN, T_OUT, LIN, SWIN ESD Protection Human Body Model ±15 IEC 1000-4-2 Air-Gap Discharge method ±15 IEC 1000-4-2 Contact Discharge method ±8 kV TIMING CHARACTERISTICS (VCC = VL = +2.35V to +3.0V, C1–C4 = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +2.5V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS RL = 3kΩ, CL = 1000pF, one transmitter switching MIN TYP MAX 250 Maximum Data Rate Receiver Propagation Delay UNITS kbps tPHL - tPLH RL = 3kΩ, CL = 150pF, one transmitter switching (Note 2) tPHL Receiver input to receiver output, CL = 150pF tPLH 460 0.15 µs 0.15 Receiver Output Enable Time 200 ns Receiver Output Disable Time 200 ns Time to Exit Shutdown Transmitter Skew Receiver Skew Transition-Region Slew Rate VT_OUT > 3.7V tPHL - tPLH RL = 3kΩ, CL = 1000pF (Note 3) tPHL - tPLH VCC = +2.5V, TA = +25°C, CL = 150pF to RL = 3kΩ to 7kΩ, 1000pF measured from +3V CL = 150pF to to -3V or -3V to +3V, 2500pF one transmitter switching 6 30 µs 100 ns 50 ns 30 V/µs 4 30 Note 2: Guaranteed by correlation. Note 3: Transmitter skew is measured at the transmitter zero crosspoint. _______________________________________________________________________________________ 3 MAX3388E/MAX3389E DC ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = VL = +2.5V, TA = +25°C, unless otherwise noted.) TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE SLEW RATE vs. LOAD CAPACITANCE MAX3386E toc02 MAX3388E toc01 16 14 2.5 12 SLEW RATE (V/µs) OUTPUT VOLTAGE (V) 5.0 DATA RATE = 460kbps LOAD = 3kΩ IN PARALLEL 0 -2.5 SLEW RATE 10 SLEW RATE + 8 6 4 2 -5.0 0 1000 2000 3000 4000 5000 0 2000 3000 4000 LOAD CAPACITANCE (pF) TRANSMITTER OUTPUT VOLTAGE vs. DATA RATE SUPPLY CURRENT vs. LOAD CAPACITANCE 60 MAX3388E toc03 5.0 LOAD = 3kΩ, 1000pF ONE TRANSMITTER SWITCHING AT DATA RATE, OTHER TRANSMITTERS AT 1/8 DATA RATE LOAD = 3kΩ ONE TRANSMITTER SWITCHING AT DATA RATE, OTHER TRANSMITTERS AT 1/8 DATA RATE 50 SUPPLY CURRENT (mA) 2.5 0 1000 LOAD CAPACITANCE (pF) 40 5000 MAX3388E toc04 0 OUTPUT VOLTAGE (V) 460kbps 30 240kbps 20 -2.5 20kbps 10 0 -5.0 50 100 150 200 250 300 350 400 450 0 1000 2000 3000 4000 DATA RATE (kbps) LOAD CAPACITANCE (pF) LIN TO LOUT tPD ON-RESISTANCE vs. SWIN VOLTAGE LIN 70 5000 MAX3388E toc06 0 MAX3388E toc05 TA = +85°C 65 TA = +25°C RON (Ω) MAX3388E/MAX3389E 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones 1V/div 60 55 TA = -40°C 50 LOUT RPULLUP = 1kΩ 45 200ns/div 0 0.5 1.0 1.5 2.0 2.5 VSWIN (V) 4 _______________________________________________________________________________________ 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones PIN NAME 1 C1+ 2 V+ +4.2V Supply Generated by the Charge Pump 3 C1- Negative Terminal of the Voltage-Doubler Charge-Pump Capacitor 4 C2+ Positive Terminal of the Inverting Charge-Pump Capacitor 5 C2- Negative Terminal of the Inverting Charge-Pump Capacitor 6 V- 7, 8, 9 T1IN, T2IN, T3IN FUNCTION Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor -4.2V Supply Generated by the Charge Pump CMOS Transmitter Inputs 10 LOUT 11 SWOUT Switch Output 12, 13 R2OUT, R1OUT CMOS Receiver Outputs. Swing between 0 and VL. 14 VL 15 SWIN Handshaking Output. This output is active during shutdown for the MAX3389E. Logic-Level Supply. All CMOS inputs and outputs are referred to this supply. VL = +1.8V to +3.0V. Switch Input. 16 LIN 17, 18 R2IN, R1IN Handshaking Input. This input is active during shutdown for the MAX3389E. 19, 20, 21 T3OUT, T2OUT, T1OUT 22 GND Ground 23 VCC +2.35V to +3V Supply Voltage 24 SHDN RS-232 Receiver Inputs RS-232 Transmitter Outputs Shutdown Input. 0 = shutdown, switch open; 1 = normal operation, switch closed. _______________________________________________________________________________________ 5 MAX3388E/MAX3389E Pin Description MAX3388E/MAX3389E 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones Table 1. Shutdown Logic Truth Table SHDN TRANSMITTER OUTPUTS RECEIVER OUTPUTS CHARGE PUMP SWITCH L High-Z High-Z Inactive H Active Active Active POWERMANAGEMENT UNIT OR KEYBOARD CONTROLLER LOUT MAX3389E Open MAX3388E High-Z Closed LIN LIN LIN 5V/div SHDN T1 I/O CHIP POWER SUPPLY VL 2V/div MAX3388E MAX3389E T2 VCC = +2.5V C1–C4 = 0.1µF CL = 1000pF, RL = 3kΩ I/O CHIP WITH UART RS-232 CPU Figure 2. Transmitter Outputs when Exiting Shutdown Figure 1. Interface Under Control of PMU Detailed Description Dual Charge-Pump Voltage Converter The MAX3388E/MAX3389E’s internal power supply consists of a regulated dual charge pump that provides output voltages of +4.2V (doubling charge pump) and 4.2V (inverting charge pump), regardless of the input voltage (VCC) over a +2.5V to +3.0V range. The charge pumps operate in a discontinuous mode: if the output voltages are less than 4.2V, the charge pumps are enabled; if the output voltages exceed 4.2V, the charge pumps are disabled. Each charge pump requires flying capacitors (C1, C2) and reservoir capacitors (C3, C4) to generate the V+ and V- supplies. RS-232 Transmitters The transmitters are inverting level translators that convert CMOS-logic levels to ±3.7V EIA/TIA-232-compatible levels. 6 10µs/div The MAX3388E/MAX3389E’s transmitters guarantee a 250kbps data rate with loads of 3kΩ in parallel with 1000pF and 460kbps data rate with loads of 3kΩ in parallel with 150pF. Figure 1 shows a complete system connection. These RS-232 output stages are turned off (high impedance) when the devices are in shutdown mode. When the power is off, the MAX3388E/MAX3389E permit the outputs to be driven up to ±12V. The transmitter inputs do not have pullup resistors. Connect unused inputs to GND or VL. RS-232 Receivers The receivers convert RS-232 signals to CMOS-logic output levels. The MAX3388E/MAX3389E’s receivers have inverting outputs. The outputs are high impedance in shutdown. Shutdown Mode Supply current falls to less than 1µA when the MAX3388E/MAX3389E are placed in shutdown mode (SHDN logic low). When shut down, the device’s charge pumps are turned off, V+ decays to VCC, V- is pulled to ground, the switch is opened, and the transmitter outputs are disabled (high impedance). The time required to exit _______________________________________________________________________________________ 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones VL Logic Supply Input Unlike other RS-232 interface devices where the receiver outputs swing between 0 and V CC, the MAX3388E/ MAX3389E feature a separate logic supply input (VL) that sets VOH for the receiver outputs and sets thresholds for the transmitter inputs. This feature allows a great deal of flexibility in interfacing to many different types of systems with different logic levels. Connect this input to the host logic supply (1.8V ≤ VL ≤ VCC). Also see the Typical PDA/Cell-Phone Application section. RC 1MΩ RD 1500Ω CHARGE-CURRENT LIMIT RESISTOR DISCHARGE RESISTANCE HIGHVOLTAGE DC SOURCE Cs 100pF MAX3388E/MAX3389E shutdown is typically 30µs, as shown in Figure 2. Connect SHDN to VCC if the shutdown mode is not used. In shutdown mode, the receiver outputs are high impedance (Table 1). DEVICE UNDER TEST STORAGE CAPACITOR Figure 3a. Human Body ESD Test Model ±15kV ESD Protection As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against ESDs encountered during handling and assembly. The MAX3388E/ MAX3389E’s driver outputs, receiver inputs, the handshaking input LIN, and the switch terminal SWIN have extra protection against static electricity. Maxim has developed state-of-the-art structures to protect these pins against an 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” version devices 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 outputs and receiver inputs of this product family 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 3) ±15kV using IEC 1000-4-2’s Air-Gap Discharge method ESD Test Conditions ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, methodology, and results. Human Body Model Figure 3a shows the Human Body Model, and Figure 3b 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 1.5kΩ resistor. IP 100% 90% Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) AMPERES 36.8% 10% 0 0 tRL TIME tDL CURRENT WAVEFORM Figure 3b. Human Body Current Waveform IEC 1000-4-2 The IEC 1000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to ICs. The MAX3388E/MAX3389E helps you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without the need for additional ESDprotection components. The major difference between tests done using the Human Body Model and IEC 1000-4-2 is higher peak current in IEC 1000-4-2, because series resistance is lower in the IEC 1000-4-2 model. Hence, the ESD withstand voltage measured to IEC 1000-4-2 is generally lower than that measured using the Human Body Model. Figure 4a shows the IEC 1000-4-2 model, and Figure 4b shows the current waveform for the ±8kV IEC 1000-4-2 Level 4 ESD Contact Discharge test. _______________________________________________________________________________________ 7 RC 50MΩ to 100MΩ RD 330Ω CHARGE-CURRENT LIMIT RESISTOR DISCHARGE RESISTANCE HIGHVOLTAGE DC SOURCE Cs 150pF The Air-Gap test 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 by contact that occurs with handling and assembly during manufacturing. All pins require this protection during manufacturing, not just RS-232 inputs and outputs. Therefore, after PC board assembly, the Machine Model is less relevant to I/O ports. DEVICE UNDER TEST STORAGE CAPACITOR __________Applications Information Figure 4a. IEC 1000-4-2 ESD Test Model Capacitor Selection I 100% 90% I PEAK MAX3388E/MAX3389E 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones 10% t R = 0.7ns to 1ns t 30ns 60ns Power-Supply Decoupling Figure 4b. IEC 1000-4-2 ESD Generator Current Waveform Table 2. Minimum Required Capacitor Values 8 The capacitor type used for C1–C4 is not critical for proper operation; polarized or nonpolarized capacitors can be used. The charge pump requires 0.1µF capacitors for 2.5V operation (Table 2). Do not use values smaller than those listed in Table 2. Increasing the capacitor values (e.g., by a factor of 2) reduces ripple on the transmitter outputs and slightly reduces power consumption. C2, C3, and C4 can be increased without changing C1’s value. However, do not increase C1 without also increasing the values of C2, C3, and C4 to maintain the proper ratios (C1 to the other capacitors). When using the minimum required capacitor values, make sure the capacitor value does not degrade excessively with temperature. If in doubt, use capacitors with a larger nominal value. The capacitor’s equivalent series resistance (ESR), which usually rises at low temperatures, influences the amount of ripple on V+ and V-. VCC (V) C1–C4 (µF) 2.5 to 3.0 0.1 In most circumstances, a 0.1µF bypass capacitor is adequate. In applications that are sensitive to powersupply noise, decouple VCC to ground with a capacitor of the same value as charge-pump capacitor C1. Connect bypass capacitors as close to the IC as possible. Transmitter Outputs when Exiting Shutdown Figure 2 shows two transmitter outputs when exiting shutdown mode. As they become active, the two transmitter outputs are shown going to opposite RS-232 levels (one transmitter input is high; the other is low). Each transmitter is loaded with 3kΩ in parallel with 1000pF. The transmitter outputs display no ringing or undesirable transients as they come out of shutdown. Note that the transmitters are enabled only when the magnitude of V- exceeds approximately 2.5V. _______________________________________________________________________________________ 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones VCC 0.1µF VCC C1+ C1 C1- Power Switch The MAX3388E/MAX3389E contain an internal switch for powering external circuitry. This can be used to power hot-sync circuitry or other low-power circuitry. The switch on- resistance is typically 62Ω. The SWIN side of the switch is ESD protected to ±15kV. MAX3388E/MAX3389E High Data Rates The MAX3388E/MAX3389E maintain RS-232-compatible transmitter output voltages even at high data rates. Figure 5 shows a transmitter loopback test circuit. Figure 6 shows a loopback test result at 250kbps, and Figure 7 shows the same test at 460kbps. For Figure 6, all transmitters were driven simultaneously at 250kbps into RS-232 loads in parallel with 1000pF. For Figure 7, a single transmitter was driven at 460kbps, and all transmitters were loaded with an RS-232 receiver in parallel with 150pF. V+ C3 MAX3388E MAX3389E C2+ VC4 C2 C2- T_ OUT T_ IN Logic-Level I/O In addition to the traditional RS-232 I/O, the MAX3388E/MAX3389E have a logic-level transceiver from the RS-232 connector side to the CMOS-logic side. The input impedance is typically 30kΩ, and the output is open drain. The logic level I/O is active during shutdown for the MAX3389E. This I/O transceiver is useful for hot syncing or other dedicated communication capability. The input is ESD protected to ±15kV. R_ IN R_ OUT 5kΩ VCC SHDN CL GND Typical PDA/Cell-Phone Application The MAX3388E/MAX3389E designed with PDA applications in mind. Two transmitters and two receivers handle standard full-duplex communication protocol, while an extra transmitter allows a ring indicator (RI) signal to alert the UART on the PC. Without the ring indicator transmitter, solutions for these applications would require software-intensive polling of the cradle inputs. The RI signal is generated when a PDA, cellular phone, or other “cradled” device is plugged into its cradle. This generates a logic-low signal to RI transmitter input, creating +3.7V at the ring indicate pin. The PC’s UART RI input is the only pin that can generate an interrupt from signals arriving through the RS-232 port. The interrupt routine for this UART will then service the RS-232 full-duplex communication between the PDA and the PC. As cell phone design becomes more like that of PDAs, cell phones will require similar docking ability and communication protocol. Cell phones operate on a single lithium-ion (Li+) battery and generate a regulated output voltage of +2.35V to +3V from the phone connector. The baseband logic coming from the phone connector can be as low as 1.8V at the transceivers. To prevent forward biasing of a device internal to the cell phone, the MAX3388E/MAX3389E come with a logic powersupply pin (VL) that limits the logic levels presented to Figure 5. Loopback Test Circuit T1IN 2V/div T1OUT 5V/div R1OUT 5V/div CL = 1000pF 1µs/div Figure 6. Loopback Test Results at 250kbps _______________________________________________________________________________________ 9 MAX3388E/MAX3389E 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones T1IN 2V/div T1OUT 5V/div the phone. The receiver outputs will sink to zero for low outputs, but will not exceed VL for logic highs. The input logic levels for the transmitters are also altered, scaled by the magnitude of the VL input. The devices will work with VL as low as 1.8V. This is useful with cell phones and other power-efficient devices with core logic voltage levels that go as low as 1.8V. Chip Information TRANSISTOR COUNT: 1323 R1OUT 5V/div CL = 150pF 1µs/div Figure 7. Loopback Test Results at 460kbps 10 ______________________________________________________________________________________ 2.5V, ±15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones TSSOP.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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________11 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX3388E/MAX3389E Package Information