EVALUATION KIT AVAILABLE 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 General Description Benefits and Features The MAX3250 is a 3.0V to 5.5V powered, 50V isolated EIA/TIA-232 and V.28/V.24 communications interface with high data-rate capabilities. The MAX3250 is a dual die part that operates with up to 50V difference between the RS-232 side and the logic side (ISOCOM to GND). This makes the device ideal for operation in noisy conditions with high common-mode voltages. This feature prevents damage to the device if RS-232 lines are inadvertently short-circuited to a +24V or 48V power bus. The MAX3250 is powered by a single 3V to 5.5V supply on the logic side. Power is transferred from the logic side to the isolated side by 100V external capacitors. * Isolation Breaks Ground Loops Due to High Common- The MAX3250 has two receivers (Rx) and two drivers (Tx) and is guaranteed to run at data rates of 250kbps while maintaining RS-232 output levels. The transceivers have a proprietary low-dropout transmitter output stage, delivering true RS-232 performance from a 3V to 5.5V supply with a dual charge pump. The device features a FAULT open-drain output to signal an excessive isolated-side voltage condition on any of the RS232 inputs. This output can drive an alarm LED or can be monitored by the processor to prevent operation under these conditions. The receiver outputs are high impedance in shutdown, allowing multiple interfaces (IrDA, RS-232, RS-485) to be connected to the same UART. The MAX3250 is available in a space-saving 28-pin SSOP package. Applications Industrial Control Mode Voltages While Maintaining Data Rate * 50V Isolation * 250kbps Guaranteed Data Rate * FAULT Output Signals Excessive Isolated-Side Voltage * Integration of Isolation and RS-232 Saves Space * SSOP Package * Shutdown Allows Multiple Interfaces (IrDA, RS-232, RS-485) to be Connected to the Same UART * High-Impedance Transmitter and Receiver Outputs in Shutdown * 20A Supply Current in Shutdown * Inductorless/Transformerless Design Simplifies EMI Compliance * Low-Cost Replacement for Opto-Isolated Transceivers * Meets EIA/TIA-232 Specifications Down to 3.0V Pin Configuration TOP VIEW + C1- 1 28 VCC R1OUT 2 27 C2- R2OUT 3 26 GND Programmable Logic Controller T1IN 4 Point-of-Sale Equipment T2IN 5 PC-to-Router Connections N.C. 6 23 N.C. Diagnostic Ports N.C. 7 22 N.C. Telecom Equipment C1+ 8 21 C2+ C3+ 9 20 ISOVCC Ordering Information PART TEMP RANGE PIN-PACKAGE C3- 11 18 R2IN 17 T1OUT 16 T2OUT 0C to +70C 28 SSOP MAX3250EAI+ -40C to +85C 28 SSOP C4- 13 19-2443; Rev 4; 2/15 24 SHDN 19 R1IN MAX3250CAI+ Typical Operating Circuit appears at end of data sheet. MAX3250 V+ 10 C4+ 12 +Denotes a lead(Pb)-free/RoHS-compliant package. 25 FAULT V- 14 15 ISOCOM SSOP 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 Absolute Maximum Ratings C1+, C2+, C3+, C3-, C4+, C4(All voltages referenced to GND, unless otherwise noted.) to ISOCOM .....................................-0.3V to (ISOVCC + 0.3V) VCC ...........................................................................-0.3V to +6V ISOCOM...............................................................................80V T_OUT Current ..............30mA (continuous), 50mA (peak, 10s) ISOVCC to ISOCOM.................................................-0.3V to +6V R_IN Current..................30mA (continuous), 50mA (peak, 10s) V+ to ISOCOM (Note 1)............................................-0.3V to +7V ISOCOM Current ...........30mA (continuous), 50mA (peak, 10s) V- to ISOCOM (Note 1)............................................+0.3V to -7V Short-Circuit Duration T_OUT to ISOCOM .................Continuous V+ + |V-| (Note 1) ...................................................................13V Continuous Power Dissipation (TA = +70C) 28-Pin SSOP (derate 15mW/C above +70C) .......1201.2mW Input Voltages Operating Temperature Ranges T_IN, SHDN ...........................................................-0.3V to +6V MAX3250CAI .....................................................0C to +70C R_IN to ISOCOM...............................................................25V MAX3250EAI...................................................-40C to +85C Output Voltages Storage Temperature Range .............................-65C to +150C T_OUT to ISOCOM ........................................................13.2V Lead Temperature (soldering, 10s) .................................+300C R_OUT .....................................................-0.3V to (VCC + 0.3V) FAULT....................................................................-0.3V to +6V Soldering Temperature (reflow) .......................................+260C C1-, C2- ......................................................-0.3V to (VCC + 0.3V) Note 1: V+ and V- can have a maximum magnitude 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. Electrical Characteristics (VCC = 3.0V to 5.5V, see Typical Operating Circuit and Table 1 for capacitor values, ISOCOM = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25C.) (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS mA DC CHARACTERISTICS Supply Current Supply Current Shutdown SHDN = VCC, no load 15 35 SHDN = GND, VISOCOM = GND 20 45 SHDN = GND, VISOCOM = 50V Maximum Ground Differential |VGND - VISOCOM| Isolation Resistance Between GND and ISOCOM 350 50 60 A V k LOGIC INPUTS Input Logic Low Input Logic High T_IN, SHDN T_IN, SHDN 0.8 VCC = 3.3V 2.0 VCC = 5.0V 2.4 Transmitter Input Hysteresis V V 0.5 V T_IN, SHDN -1 0.01 +1 A Output Leakage Current SHDN = GND -10 0.05 +10 A Output-Voltage Low IOUT = 1.6mA 0.4 V Output-Voltage High IOUT = -1.0mA FAULT OUTPUT Output-Voltage Low (Open Drain) Output Leakage Current IOUT = 5mA FAULT Trip Level |VGND - VISOCOM| Input Leakage Current RECEIVER OUTPUTS www.maximintegrated.com VCC - 0.6 VCC - 0.1 FAULT not asserted 55 V 0.4 V 1 A V Maxim Integrated | 2 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 Electrical Characteristics (continued) (VCC = 3.0V to 5.5V, see Typical Operating Circuit and Table 1 for capacitor values, ISOCOM = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25C.) (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS +25 V RECEIVER INPUTS (relative to ISOCOM) Input-Voltage Range -25 Input Threshold Low TA = +25C Input Threshold High TA = +25C VCC = 3.3V 1.2 0.6 VCC = 5.0V 1.3 0.8 VCC = 3.3V 2.4 1.6 VCC = 5.0V 2.4 1.7 Input Hysteresis Input Resistance V 0.5 TA = +25C 3 5 V V 7 k TRANSMITTER OUTPUTS (relative to ISOCOM) Output-Voltage Swing All transmitter outputs loaded with 3k to ISOCOM, TA = +25C 5.0 5.4 Output Resistance ISOVCC = V+ = V- = 0V, VT_OUT = 2V 300 10M Output Short-Circuit Current Output Leakage Current VCC = 0 or 3V to 5.5V, VT_OUT = 12V, SHDN = GND V -60 +60 mA -25 +25 A Timing Characteristics (VCC = 3.0V to 5.5V, see Typical Operating Circuit and Table 1 for capacitor values, ISOCOM = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS Maximum Data Rate RL = 3k, CL = 1000pF to ISOCOM, one transmitter, TA = +25C Receiver Propagation Delay R_IN to R_OUT, CL = 150pF to GND 0.4 Receiver Skew |tPHL - tPLH| 100 ns Transmitter Skew |tPHL - tPLH| (Note 3) 120 ns Transition-Region Slew Rate VCC = 3.3V, TA = +25C, RL = 3k to 7k to ISOCOM, measured from +3V to -3V or -3V to +3V 250 kbps s CL = 150pF to 1000pF to ISOCOM 6 30 CL = 150pF to 2500pF to ISOCOM 4 30 V/s FAULT Propagation Delay 0.3 s Time to Shutdown 0.5 s Time to Exit Shutdown VISOCOM = GND 300 VISOCOM = 50V 350 s Note 2: All currents into the device are positive; all currents out of the device are negative. All voltages are referenced to device ground, unless otherwise noted. Note 3: Transmitter skew is measured at the transmitter zero crosspoints. www.maximintegrated.com Maxim Integrated | 3 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 Typical Operating Characteristics (VCC = 3.3V, 250kbps data rate, see Typical Operating Circuit and Table 1 for capacitor values, all transmitters loaded with 3k and CL to ISOCOM, TA = +25C, unless otherwise noted.) SLEW RATE vs. LOAD CAPACITANCE 2 0 20 -SLEW 15 +SLEW 10 -2 T1 TRANSMITTING AT 250kbps T2 TRANSMITTING AT 20kbps 80 SUPPLY CURRENT (mA) T1 TRANSMITTING AT 250kbps T2 TRANSMITTING AT 20kbps 90 MAX3250 toc02 25 SLEW RATE (V/s) VOUT+ 4 30 MAX3250 toc01 6 70 60 250kbps 50 40 120kbps 30 20 20kbps 5 -4 0 -6 0 0 0 1000 2000 10 FOR DATA RATES UP TO 250kbps VOUT3000 4000 1000 5000 2000 3000 4000 5000 0 1000 LOAD CAPACITANCE (pF) 2000 3000 4000 5000 LOAD CAPACITANCE (pF) LOAD CAPACITANCE (pF) SHUTDOWN CURRENT vs. TEMPERATURE TIME TO EXIT SHUTDOWN VISOCOM = 0V MAX3250 toc04 ISOCOM = -50V 300 SUPPLY CURRENT (A) TOUT 5V/div MAX3250 toc05 400 SHDN 5V/div 200 100 ISOCOM = 0V 0 -100 -200 ISOCOM = +50V -300 100s/div -40 -15 10 35 85 60 TEMPERATURE (C) TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE COMMON-MODE FAULT RESPONSE 6 VOUT+ 4 MAX3250 toc07 MAX3250 toc01 8 TRANSMITTER OUTPUT VOLTAGE (V) TRANSMITTER OUTPUT VOLTAGE (V) 8 OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE MAX3250 toc03 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE ISOCOM 50V/div T1 TRANSMITTING AT 250kbps T2 TRANSMITTING AT 20kbps 2 0 -2 FAULT 5V/div -4 VOUT- -6 0 1000 2000 3000 4000 5000 4ms/div LOAD CAPACITANCE (pF) www.maximintegrated.com Maxim Integrated | 4 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 Pin Description PIN NAME FUNCTION 1 C1- 2 R1OUT 3 R2OUT TTL/CMOS Receiver Output 4 T1IN TTL/CMOS Transmitter Input 5 T2IN TTL/CMOS Transmitter Input 6, 22, 23 N.C. No Connection. Not internally connected. 7 N.C. No Connection. Leave unconnected or connect to ISOCOM. 8 C1+ Positive Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C1+ to C1-. See Table 1 for values. 9 C3+ Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor. Connect a 0.1F capacitor from C3+ to C3-. 10 V+ +5.5V Generated by the Charge Pump, Referenced to ISOCOM. Bypass V+ to ISOCOM with a 0.47F capacitor. 11 C3- Negative Terminal of the Voltage-Doubler Charge-Pump Capacitor. Connect a 0.1F capacitor from C3- to C3+. 12 C4+ Positive Terminal of the Inverting Charge-Pump Capacitor. Connect a 0.47F capacitor from C4+ to C4-. 13 C4- Negative Terminal of the Inverting Charge-Pump Capacitor. Connect a 0.47F capacitor from C4- to C4+. 14 V- 15 ISOCOM 16 T2OUT 17 T1OUT 18 R2IN 19 R1IN Negative Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C1- to C1+. See Table 1 for values. TTL/CMOS Receiver Output -5.5V Generated by the Charge Pump, Referenced to ISOCOM. Bypass V- to ISOCOM with a 0.47F capacitor. Isolated Ground RS-232 Transmitter Output RS-232 Transmitter Output RS-232 Receiver Input RS-232 Receiver Input Internally Generated Isolated Power-Supply Voltage, Referenced to ISOCOM. Bypass ISOVCC to ISOCOM with a 2.2F capacitor. 20 ISOVCC 21 C2+ 24 SHDN Shutdown Control. Drive SHDN low to enter low-power shutdown mode. Drive SHDN high or connect to VCC for normal operation. 25 FAULT Overvoltage Indicator. Active low, open drain. 26 GND Ground 27 C2- Negative Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C2- to C2+. See Table 1 for values. 28 VCC 3.0V to 5.5V Supply Voltage. Bypass VCC to GND with a 1F capacitor. www.maximintegrated.com Positive Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C2+ to C2-. See Table 1 for values. Maxim Integrated | 5 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 TIN1 TOUT1 RIN1 ROUT1 TIN2 TOUT2 ROUT2 RIN2 SHDN ISOVCC FAULT OSC V+ MAX3250 RS-232 CHARGE PUMP VCC POWER CONTROLLER FAULT DETECTOR GND C1- C2- C1+ C2+ C3+ C3C4+ C4V- ISOCOM Figure 1. Functional Diagram Detailed Description The MAX3250 is a 3.0V to 5.5V powered, 50V isolated EIA/TIA-232 and V.28/V.24 communications interface with high data-rate capabilities. The MAX3250 is a dual die part that operates with up to 50V difference between the RS-232 side and the logic side (ISOCOM to GND). This makes the device ideal for operation in noisy conditions with high common-mode voltages. This feature prevents damage to the device if RS-232 lines are inadvertently short-circuited to a +24V or 48V power bus. The MAX3250 typically draws 15mA of supply current when unloaded. Supply current drops to 20A when the device is placed in shutdown mode. www.maximintegrated.com The MAX3250 has two receivers and two drivers and is guaranteed to operate at data rates up to 250kbps. The device features a FAULT open-drain output to signal an excessive isolated-side voltage condition on any of the RS-232 inputs. This output can drive an alarm LED or can be monitored by the processor to prevent operation under these conditions. The receiver outputs are high impedance in shutdown, allowing multiple interfaces (IrDA, RS-232, RS-485) to be connected to the same UART (Figure 1). The MAX3250 is a low-cost replacement for opto-isolated transceivers. Isolated Power Supply The MAX3250 drives a high-frequency square wave into C1 and a complementary square wave into C2. These Maxim Integrated | 6 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 AC waveforms are rectified on the isolated side of the dual die to power its internal circuitry (ISOVCC). Capacitor C6 filters the output of the rectifier. See the Typical Operating Circuit. The power controller works in a dual power mode. Power is maximum when the isolated power supply is below its regulation point. Power is reduced when the isolated power supply is above its regulation point. Dual Charge-Pump Voltage Converter The RS-232 drivers are powered from a regulated dual charge pump that provides output voltages of +5.5V (doubling charge pump) and -5.5V (inverting charge pump) relative to ISOCOM over the 3.0V to 5.5V VCC range. The charge pumps are powered from ISOVCC and operate in a discontinuous mode. If the output voltages are less than 5.5V, the charge pumps are enabled. If the output voltages exceed 5.5V, the charge pumps are disabled. Each charge pump requires a flying capacitor (C3, C4) and a reservoir capacitor (C7, C8) to generate the V+ and V- supplies. RS-232 Transmitters The transmitters are inverting level translators that convert TTL/CMOS-logic levels to 5.0V EIA/TIA-232-compliant levels. They guarantee a 250kbps data rate with worstcase loads of 3k in parallel with 1000pF to ISOCOM. In shutdown, the transmitters are disabled and the outputs are forced into a high-impedance state. When powered off or shut down, the outputs can be driven up to 12V relative to ISOCOM. The transmitter inputs do not have pullup resistors. All unused inputs should be connected to VCC or GND. RS-232 Receivers The receivers convert RS-232 signals to CMOS-logic output levels. The receivers' outputs are forced into a high-impedance state when the device is in shutdown. This allows a single UART to multiplex between different protocols. Low-Power Shutdown Mode Shutdown mode is obtained by driving SHDN low. In shutdown, the devices typically draw only 20A of supply current and no power is transferred across the isolation capacitors. The charge pumps are disabled, and the receiver outputs and transmitter outputs are high impedance. When exiting shutdown the charge pumps and transmitter outputs are fully operational in typically 500s (Figure 3). Connect SHDN to VCC if the shutdown mode is not used. Applications Information Power Isolation Capacitors The values for capacitors C1 and C2 are important for proper operation of the device. These capacitors should be 0.047F for 4.5V to 5.5V operation, and 0.47F for 3.0V to 3.6V operation. Smaller values result in insufficient supply voltage on the isolated side. Larger values are not allowed. Capacitor C9 provides an AC feedback path for proper controller operation. Connect C9 from ISOCOM to GND. The values for C1, C2, and C9 determine the maximum frequency and amplitude of the voltage difference between the local and isolated ground. Table 1 shows proper capacitance values. TRANSMITTER OUTPUT VOLTAGE (V) 6 5 VCC = 3.0V SHDN 5V/div VOUT+ 4 3 T1OUT 2 1 0 -1 VCC T1 VOUT1+ T2 VOUT2- -2 -3 -4 -5 2V/div VOUTVCC = 3.3V T2OUT -6 0 1 2 3 4 5 6 7 8 100s/div LOAD CURRENT PER TRANSMITTER (mA) Figure 2. Transmitter Output Voltage vs. Load Current per Transmitter www.maximintegrated.com Figure 3. Transmitter Outputs when Exiting Shutdown or Powering Up Maxim Integrated | 7 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 Table 1. Required Capacitor Values VCC (V) C1, C2 (F) C3 (F) C4, C7, C8 (F) C5 (F) C6 (F) C9 (nF) 3.0 to 3.6 0.47 0.1 0.47 1 2.2 10 0.47 1 2.2 10 4.5 to 5.5 0.047 0.1 To achieve full isolation capability, C1, C2, and C9 should be rated for 100V or higher operation and be X7R or X5R type or metalized film dielectric. Y5V and Z5U dielectrics should be avoided as their voltage and temperature coefficients make their power-transfer capabilities insufficient. Charge-Pump and Bypass Capacitors Capacitors C3-C8 should be X7R or X5R type dielectric. Their voltage rating needs to be 10V or higher. Layout Information Because the MAX3250 is intended for systems requiring 50V isolation, some consideration in component placement is necessary. A 20mil air gap should isolate the logic side and the isolated RS-232 side, across the N.C. pins (pin numbers 6, 7, 22, and 23) of the MAX3250. The only components that cross this air gap should be C1, C2, and C9, which should all have a minimum 100V rating. All capacitors should be located as close to the MAX3250 as possible. www.maximintegrated.com Maximum Voltage Between ISOCOM and Logic GND High values of applied isolation voltage and frequency can cause ripple on ISOVCC, V+, V-, and in extreme cases on VCC. Therefore, it is recommended that the isolation-voltage and frequency be limited to the values shown in the Typical Operating Characteristics. Insert a 1k 1/4W resistor in series with any isolation test voltage when testing for maximum values of applied isolation voltage. Exceeding the maximum limits of voltage and frequency (see the Typical Operating Characteristics) could trigger a holding current in the internal ESD-protection device if the 80V isolation limit is exceeded. This resistor should not be used in normal application. Transmitter Outputs when Exiting Shutdown Figure 3 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 3k in parallel with 2500pF. 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 -3V. Maxim Integrated | 8 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 Typical Operating Circuit REMOTE XCVR VCC C5 1F CABLE VCC REMOTE MICRO RIN1 TOUT1 FAULT RIN2 MICRO SHDN TIN1 ROUT1 TIN2 ROUT2 C1 0.47F C2 0.47F TOUT2 C4+ C4 0.47F MAX3250 C4C3+ C3 0.1F C3V+ C1+ C1C2+ VISOVCC C6 2.2F C2GND C8 0.47F C7 0.47F ISOCOM C9 10nF 50V GND OFFSET REMOTE GROUND Chip Information Package Information PROCESS: BiCMOS For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.com PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 28 SSOP A28M+3 21-0056 90-0095 Maxim Integrated | 9 50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver MAX3250 Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 4/02 Initial release -- 1 2/03 Updated Design -- 2 1/08 Updated EC table 3 3 9/11 Added lead-free packaging information; corrected pin names, power dissipation, and soldering temperature in Absolute Maximum Ratings; updated capacitor values in data sheet. 4 2/15 Updated Benefits and Features section DESCRIPTION 1, 2, 3, 5-9 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2015 Maxim Integrated Products, Inc. | 10 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX3250CAI+ MAX3250EAI+ MAX3250CAI+T MAX3250EAI+T