19-1941; Rev 1; 3/06 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces The MAX3480EA/MAX3480EB are electrically isolated RS-485/RS-422 data-communications interfaces. The RS-485/RS-422 I/O pins are protected against 15kV electrostatic discharge (ESD) shocks, without latchup. Transceivers, optocouplers, and a transformer are all included in one low-cost, 28-pin PDIP package. A single +3.3V supply on the logic side powers both sides of the interface. The MAX3480EB features reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission at data rates up to 160kbps. The MAX3480EA's driver slew rate is not limited, allowing transmission rates up to 2.5Mbps. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The MAX3480EA/MAX3480EB are guaranteed to withstand 1260VRMS (1min) or 1520VRMS (1s). Their isolated inputs and outputs meet RS-485/RS-422 specifications. ________________________Applications Isolated RS-485/RS-422 Data Interface Transceivers for EMI-Sensitive Applications Industrial-Control Local Area Networks Automatic Test Equipment HVAC/Building Control Networks Telecom Ordering Information PART TEMP RANGE DATA PINPKG RATE CODE PACKAGE* (kbps) 0C to +70C 28 PDIP 2500 P28M-1 MAX3480EAEPI -40C to +85C 28 PDIP 2500 P28M-1 MAX3480EACPI 0C to +70C 28 PDIP 250 P28M-1 MAX3480EBEPI -40C to +85C 28 PDIP 250 P28M-1 MAX3480EBCPI *See the Reliability section at end of data sheet. ____________________________Features Isolated Data Interface Guaranteed to 1260VRMS (1min) 15kV ESD Protection for I/O Pins Slew-Rate-Limited Data Transmission (160kbps for MAX3480EB) High-Speed, Isolated, 2.5Mbps RS-485 Interface (MAX3480EA) Single +3.3V Supply Current Limiting and Thermal Shutdown for Driver Overload Protection Standard 28-Pin PDIP Package Allows Up to 128 Transceivers on the Bus Pin Configuration TOP VIEW MAX3480EA MAX3480EB VCC1 1 28 AC1 VCC2 2 27 AC2 D1 3 26 ISO VCC1 D2 4 25 B GND1 5 24 ISO RO DRV MAX845 MAX1487E MAX487E 23 A FS 6 SD 7 22 ISO DI IN VCC3 8 21 ISO DE IN DI 9 20 ISO COM1 VCC4 10 19 ISO DI DRV 18 ISO VCC2 DE 11 17 ISO DE DRV GND2 12 16 ISO COM2 RO 13 VCC5 14 15 ISO RO LED ISOLATION BARRIER PDIP ________________________________________________________________ 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 MAX3480EA/MAX3480EB General Description MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces ABSOLUTE MAXIMUM RATINGS With Respect to GND Supply Voltage (VCC1, VCC2, VCC4, VCC5) .......-0.3V to +3.8V Supply Voltage (VCC3) ........................................-0.3V to +7V Control Input Voltage (SD, FS) ............-0.3V to (VCC3 + 0.3V) Receiver Output Voltage (RO).............-0.3V to (VCC5 + 0.3V) With Respect to ISO COM Control Input Voltage (ISO DE _)......-0.3V to (ISO VCC_ + 0.3V) Driver Input Voltage (ISO DI _) .....-0.3V to (ISO VCC_ + 0.3V) Receiver Output Voltage (ISO RO _) ..-0.3V to (ISO VCC_ + 0.3V) Driver Output Voltage (A, B)..............................-8V to +12.5V Receiver Input Voltage (A, B)............................-8V to +12.5V LED Forward Current (DI, DE, ISO RO LED) ......................50mA Continuous Power Dissipation (TA = +70C) 28-Pin PDIP (derate 9.09mW/C above +70C)............727mW Operating Temperature Ranges MAX3480E_CPI..................................................0C to +70C MAX3480E_EPI ...............................................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+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 = VCC1 = VCC2 = VCC4 = VCC5 = +3.0V to +3.6V, FS = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) (Notes 1, 2) PARAMETER Switch Frequency Operating Supply Current Shutdown Supply Current (Note 3) SYMBOL CONDITIONS fSWL FS = 0 60 FS = VCC or open 900 ICC MAX3480EA, DE = VCC or open RL = 130 RL = 54 220 MAX3480EB, DE = VCC or open RL = 80 RL = 54 180 SD = VCC3 VFSH High VFSL Low FS Input Pullup Current IFSL FS low FS Input Leakage Current IFSM FS high Input High Voltage VIH DE, DI, Figure 1 VIL DE, DI, Figure 1 Input Low Voltage Isolation Voltage 250 200 50 10 Low Isolation Resistance RISO TA = +25C, VISO = 50VDC Isolation Capacitance CISO f = 1MHz ESD Protection ESD A, B, Y, and Z pins, tested at Human Body Model Differential Driver Output (No Load) VOD1 Differential Driver Output VOD2 Change in Magnitude of Driver Output Voltage for Complementary Output States VOD 1260 2.4 1 0.8 M 10 pF 15 kV 2 R = 27 (RS-485), Figure 3 R = 27 or 50, Figure 3 V 10,000 8 R = 50 (RS-422) V VRMS 1 100 A V 0.4 High V pA VCC - 0.4 VSDL mA A 0.8 VSDH UNITS kHz 0.2 TA = +25C, 1min (Note 4) 2 MAX 2.4 VISO Shutdown Input Threshold TYP fSWH ISHDN FS Input Threshold MIN 1.5 5.0 Differential 0.3 Common mode 0.3 V V V _______________________________________________________________________________________ 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces (VCC = VCC1 = VCC2 = VCC4 = VCC5 = +3.0V to +3.6V, FS = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) (Notes 1, 2) PARAMETER Driver Common-Mode Output Input Current (A, B) SYMBOL VOC ISO IIN CONDITIONS MIN TYP R = 27 or 50, Figure 4 DE = 0, VCC = 0 or +3.6V MAX3480EA MAX3480EB VIN = +12V MAX UNITS 4 V 0.25 VIN = -7V -0.2 VIN = +12V 0.25 VIN = -7V mA -0.2 Receiver Input Resistance RIN -7V VCM 12V 48 Receiver Differential Threshold VTH -7V VCM 12V -0.2 Receiver Input Hysteresis VTH VCM = 0 Receiver Output Low Voltage VOL DI = VCC 0.4 V Receiver Output High Current IOH VOUT = +3.6V, DI = 0 250 A Driver Short-Circuit Current ISO IOSD k +0.2 70 -7V VO 12V (Note 5) V mV 100 mA SWITCHING CHARACTERISTICS--MAX3480EA (VCC = VCC1 = VCC2 = VCC4 = VCC5 = +3.0V to +3.6V, FS = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) PARAMETER Driver Input to Output Propagation Delay SYMBOL tPLH tPHL CONDITIONS MIN Figures 4, 6; RDIFF = 54, CL1 = CL2 = 100pF TYP MAX 100 275 100 275 UNITS ns Driver Output Skew tSKEW Figures 4, 6; RDIFF = 54, CL1 = CL2 = 100pF (Note 5) 25 100 ns Driver Rise or Fall Time tR, tF Figures 4, 6; RDIFF = 54, CL1 = CL2 = 100pF 15 50 ns Driver Enable to Output High tZH Figures 5, 7; CL = 100pF, S2 closed 0.5 1.8 s Driver Enable to Output Low tZL Figures 5, 7; CL = 100pF, S1 closed 0.5 1.8 s Driver Disable Time from High tHZ Figures 5, 7; CL = 15pF, S2 closed 0.6 1.8 s Driver Disable Time from Low tLZ Figures 5, 7; CL = 15pF, S1 closed 0.6 1.8 s Figures 4, 8; RDIFF = 54, CL1 = CL2 = 100pF 100 225 120 225 20 100 Receiver Input to Output Propagation Delay tPLH - tPHL Differential Receiver Skew Maximum Data Rate tPLH tPHL tSKD Figures 4, 8; RDIFF = 54, CL1 = CL2 = 100pF fMAX tSKEW, tSKD 25% of data period 2.5 ns ns Mbps _______________________________________________________________________________________ 3 MAX3480EA/MAX3480EB ELECTRICAL CHARACTERISTICS (continued) MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces SWITCHING CHARACTERISTICS--MAX3480EB (VCC = VCC1 = VCC2 = VCC4 = VCC5 = +3.0V to +3.6V, FS = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) PARAMETER Driver Input to Output Propagation Delay SYMBOL tPLH tPHL CONDITIONS MIN Figures 4, 6; RDIFF = 54, CL1 = CL2 = 100pF TYP MAX 1.5 3.0 1.2 3.0 UNITS s Driver Output Skew tSKEW Figures 4, 6; RDIFF = 54, CL1 = CL2 = 100pF 300 1200 ns Driver Rise or Fall Time tR, tF Figures 4, 6; RDIFF = 54, CL1 = CL2 = 100pF 1.0 2.0 s Driver Enable to Output High tZH Figures 5, 7; CL = 100pF, S2 closed 1.2 4.5 s Driver Enable to Output Low tZL Figures 5, 7; CL = 100pF, S1 closed 1.0 4.5 s Driver Disable Time from Low tLZ Figures 5, 7; CL = 15pF, S1 closed 1.5 4.5 s Driver Disable Time from High tHZ Figures 5, 7; CL = 15pF, S2 closed 2.0 4.5 s Receiver Input to Output Propagation Delay tPLH Figures 4, 8; RDIFF = 54, CL1 = CL2 = 100pF 0.6 3.0 1.4 3.0 750 1500 tPLH - tPHL Differential Receiver Skew Maximum Data Rate tPHL tSKD Figures 4, 8; RDIFF = 54, CL1 = CL2 = 100pF fMAX tSKEW, tSKD 25% of data period 160 s ns kbps Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to logic-side ground (GND1, GND2), unless otherwise specified. Note 2: For DE and DI pin descriptions, see the Block Diagram and the Typical Application Circuit (Figure 1 for MAX3480EA/MAX3480EB). Note 3: Shutdown supply current is the current at VCC1 when shutdown is enabled. Note 4: Limit guaranteed by applying 1520VRMS for 1s. Test voltage is applied between all pins on one side of the package to all pins on the other side of the package. For example, between pins 1 and 14, and 15 and 28. Note 5: Applies to peak current. See the Typical Operating Characteristics and the Applications Information section. 4 _______________________________________________________________________________________ 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE 2.6 2.5 2.4 2.3 -70 -60 -50 -40 -30 120 100 80 60 2.2 -20 40 2.1 -10 20 2.0 0 20 40 60 0 80 -6 -4 TEMPERATURE (C) -2 0 2 4 6 4 6 8 10 12 0.6 0.5 0.4 0.3 0.2 5.00 MEASURED AT ISO RO DRV IRO = 8mA 4.75 OUTPUT HIGH VOLTAGE (V) MAX3480EA/EB toc04 RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE MEASURED AT ISO RO DRV IRO = 8mA 0.7 2 OUTPUT LOW VOLTAGE (V) RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE 0.8 0 OUTPUT HIGH VOLTAGE (V) 0.1 MAX3480EA/EB toc05 0 4.50 4.25 4.00 3.75 3.50 3.25 0 3.00 -40 -20 0 40 20 60 80 -40 -20 0 TEMPERATURE (C) OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE 40 60 80 OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE 80 MAX3480EA/EB toc06 80 20 TEMPERATURE (C) MEASURED AT ISO RO DRV 70 OUTPUT CURRENT (mA) 60 50 40 30 60 50 40 30 20 20 10 10 0 MEASURED AT ISO RO DRV 70 MAX3480EA/EB toc07 -20 OUTPUT LOW VOLTAGE (V) -40 MAX3480EA/EB toc03 160 140 OUTPUT CURRENT (mA) -80 2.7 180 MAX3480EA/EB toc02 -90 OUTPUT CURRENT (mA) 2.8 OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE -100 MAX3480EA/EB toc01 DI = HIGH OR OPEN RL = 54 2.9 OUTPUT CURRENT (mA) DIFFERENTIAL OUTPUT VOLTAGE (V) 3.0 OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE 0 0 1.0 2.0 3.0 4.0 OUTPUT LOW VOLTAGE (V) 5.0 0 1.0 2.0 3.0 4.0 5.0 DIFFERENTIAL OUTPUT VOLTAGE (V) _______________________________________________________________________________________ 5 MAX3480EA/MAX3480EB __________________________________________Typical Operating Characteristics (VCC_ = +3.3V, TA = +25C, Figure 1, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC_ = +3.3V, TA = +25C, Figure 1, unless otherwise noted.) MAX3480EA DRIVER ENABLE (AB) AND RECEIVER OUTPUT (RO) MAX3480EA/EB toc08 MAX3480EA SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX3480EA/EB toc09 DI INPUT, 2V/div 350 DE INPUT, 1V/div A, 1V/div 2V/div B RO, 74HC240, 2V/div DE HIGH, 50 LOAD 300 SUPPLY CURRENT (mA) A B, 2V/div MAX3480EA/EB toc10 MAX3480EA DRIVER INPUT (AB) AND RECEIVER OUTPUT (RO) 250 DE HIGH, 100 LOAD 200 DE LOW, DI LOW, RL = 150 DE LOW, DI HIGH, RL = 100 50 0 100ns/div CIRCUIT OF FIGURE 2, TERMINATION: 100 MAX3480EB DRIVER INPUT (AB) AND RECEIVER OUTPUT (RO) MAX3480EB DRIVER ENABLE (DE) AND DRIVER OUTPUT (AB) 3.0 DI INPUT, 2V/div 3.6 300 DE 1V/div DE HIGH, 50 LOAD SUPPLY CURRENT (mA) 250 A 2V/div B 3.4 3.8 MAX3480EB SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX3480EA/EB toc12 MAX3480EA/EB toc11 3.2 SUPPLY VOLTAGE (V) A 2V/div B 2V/div MAX3480EA/EB toc13 100ns/div CIRCUIT OF FIGURE 2, TERMINATION: 100 DE HIGH, 100 LOAD 200 150 DE LOW, DI LOW, RL = 100 DE LOW, DI HIGH, RL = RO, 74HC240, 2V/div 50 0 20s/div 1s/div 3.0 3.2 3.4 SUPPLY VOLTAGE (V) DRIVER ENABLE TIME vs. TEMPERATURE DRIVER ENABLE TIME vs. TEMPERATURE DRIVER ENABLE TIME (s) 2.0 MAX3480EB 1.5 RL = 54, DI = 0 MEASURED FROM DE TO VALID OUTPUT 1.0 0.5 MAX3480EA/EB TOC15 2.0 MAX3480EA/EB toc14 2.5 DRIVER ENABLE TIME (s) MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces MAX3480EB 1.5 RL = 54, DI = 0V MEASURED FROM DE TO VALID OUTPUT 1.0 MAX3480EA MAX3480EA 0 0.5 -40 -20 0 20 40 TEMPERATURE (C) 6 60 80 -40 -20 0 20 40 60 TEMPERATURE (C) _______________________________________________________________________________________ 80 3.6 3.8 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces PIN NAME FUNCTION PINS ON THE NONISOLATED SIDE 1 VCC1 Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 2, 10, and 14. Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1, 10, and 14. 2 VCC2 3, 4 D1, D2 Boost-Voltage Generator Outputs. See Figures 1 and 2. 5, 12 GND1, GND2 Logic-Side Ground Inputs. Must be connected; not internally connected. 6 FS Frequency Switch Input. If VFS = VCC, switch frequency is high; if FS = 0, switch frequency is low (normal connection). 7 SD Power-Supply Shutdown Input. Must be connected to logic ground. 8 VCC3 9 DI 10 VCC4 Boosted V+ Voltage Input. Must be connected as shown in Figures 1 and 2. Driver Input. With DE high, a low on DI forces output A low and output B high. Similarly, a high on DI forces output A high and output B low. Drives internal LED cathode through R1 (Table 1). Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1, 2, and 14. 11 DE Driver-Enable Input. The driver outputs, A and B, are enabled by bringing DE high. The driver outputs are high impedance when DE is low. If the driver outputs are enabled, the device functions as a line driver. While the driver outputs are high impedance, the device functions as a line receiver. Drives internal LED cathode through R2 (Table 1). 13 RO Receiver Output. If A > B by 200mV, RO is low; if A < B by 200mV, RO is high. Open collector; must have pullup (R3) to VCC (Table 1). 14 VCC5 Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1, 2, and 10. _______________________________________________________________________________________ 7 MAX3480EA/MAX3480EB ______________________________________________________________Pin Description MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces _________________________________________________Pin Description (continued) PIN NAME FUNCTION PINS ON THE ISOLATED RS-485/RS-422 SIDE 15 ISO RO LED 16 ISO COM2 Isolated Receiver-Output LED Anode (Input). If A > B by 200mV, ISO RO LED is high; if A < B by 200mV, ISO RO LED is low. Isolated-Supply Common Input. Connect to ISO COM1. Isolated Driver-Enable Drive Input. The driver outputs, A and B, are enabled by bringing DE high. The driver outputs are high impedance when DE is low. If the driver outputs are enabled, the device functions as a line driver. While the driver outputs are high impedance, the device functions as a line receiver. Open collector output; must have pullup (R4 in Figure 1) to ISO VCC and be connected to ISO DE IN for normal operation (Table 1). 17 ISO DE DRV 18 ISO VCC2 19 ISO DI DRV Isolated Driver-Input Drive. With DE high, a low on DI forces output A low and output B high. Similarly, a high on DI forces output A high and output B low. Open-collector output; must have pullup (R5 in Figure 1) to ISO VCC and be connected to ISO DI IN for normal operation (Table 1). 20 ISO COM1 Isolated-Supply Common Output. Connect to ISO COM2. If RS-485 wires have a shield, connect ISO COM1 to shield through 100 resistor. 21 ISO DE IN Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation. 22 ISO DI IN Isolated Driver Input. Connect to ISO DI DRV for normal operation. 23 A 24 ISO RO DRV 25 B Isolated-Supply Positive Input Voltage. Connect to ISO VCC1. Noninverting Driver Output and Noninverting Receiver Input Isolated Receiver-Output Drive. Connect to ISO RO LED through R6 (Table 1 and Figure 1). Inverting Driver Output and Inverting Receiver Input 26 ISO VCC1 Isolated Supply Positive Output Voltage. Connect to ISO VCC2. 27, 28 AC2, AC1 Internal Connections. Leave these pins unconnected. Note: For DE and DI pin descriptions, see Detailed Block Diagram. 8 _______________________________________________________________________________________ 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces isolation barrier (Figure 1). Power is transferred from the logic side (nonisolated side) to the isolated side of the barrier through a center-tapped transformer. Signals cross the barrier through high-speed optocouplers. A single +3.3V supply on the logic side powers both sides of the interface. The MAX3480EA/MAX3480EB are electrically isolated, RS-485/RS-422 data-communications interface solutions. Transceivers, optocouplers, a power driver, and a transformer are in one standard 28-pin PDIP package. Signals and power are internally transported across the ISO VCC1 VCC3 OSC 1.1MHz/ 1.6MHz FS MAX3480EA: MAX485E MAX3480EB: MAX487E D1 MAX845 Q N ISO DI IN B D T F/F A ISO DE IN D2 Q N ISO RO DRV R RE GND1 SD ISO COM1 EXTERNAL RS-485/RS-422 WIRING VIN +3.0V TO +3.6V C1 22F C2 0.1F D1, D2 1N914 VCC1 1 28 AC1 (MAKE NO CONNECTION) VCC2 2 27 AC2 (MAKE NO CONNECTION) D1 3 D2 BOOSTED V+ C3 0.01F GND1 VCC3 R1* DI VCC4 LOGIC I/O DE R2* DE GND2 RO RO R3* VCC5 26 ISO VCC1 B 25 ISO RO DRV 24 4 5 FS 6 SD DI TERMINATING RESISTOR (ONE RESISTOR ON EACH END) MAX3480EA/EB MAX845 MAX1487E MAX487E 7 23 A ISO DI IN 22 8 21 9 20 ISO COM1 19 ISO DI DRV 11 18 ISO VCC2 12 17 ISO DE DRV 13 16 15 LOGIC GROUND R7* SHIELD (OPTIONAL) A R6* TWISTED PAIR TO OTHER TRANSCEIVERS SH RL SHIELD (OPTIONAL) R4* R5* R8 100 ISO COM2 NOTE: RESISTOR R8 PROTECTS THE MAX3480E FROM TRANSIENT CURRENTS BETWEEN SHIELD AND A AND B. ISO RO LED ISOLATION BARRIER *SEE TABLE 1. RL B ISO DE IN 10 14 TWISTED PAIR TO OTHER TRANSCEIVERS ISOLATION COMMON C4 270pF 4kV Figure 1. Block Diagram Table 1. Pullup and LED Drive Resistors PART R1 () R2 () R3 () R4 () R5 () R6 () R7 () MAX3480EA 100 MAX3480EB 100 100 680 3600 1000 200 Open 100 2000 3600 3600 200 430 _______________________________________________________________________________________ 9 MAX3480EA/MAX3480EB _______________Detailed Description MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces The MAX3480EB features reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission at data rates up to 160kbps. The MAX3480EA's driver slew rates are not limited, allowing transmission rates up to 2.5Mbps. The frequency-select FS is connected to GND_ in normal operation, which selects a switching frequency of approximately 600kHz. Connect to high for a higher 900kHz switching frequency. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that puts the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The driver outputs are enabled by bringing DE high. Driver-enable times are typically 500ns for the MAX3480EA and 1s for the MAX3480EB. Allow time for the devices to be enabled before sending data. When enabled, driver outputs function as line drivers. Driver outputs are high impedance when DE is low. While outputs are high impedance, they function as line receivers. EXTERNAL RS-485/RS-422 WIRING VIN +3.0V TO +3.6V C1 22F 6V C2 0.1F D1, D2 1N914 74HC240 DI DE 18 2 17 4 16 6 14 8 3 12 15 5 13 7 1 28 AC1 (MAKE NO CONNECTION) VCC2 2 27 AC2 (MAKE NO CONNECTION) FS 6 VCC3 DRIVER INPUT R1* DI VCC4 DRIVER ENABLE DE GND2 20 RO 11 9 RECEIVER OUTPUT 26 ISO VCC1 B 25 D1 3 SD R2* RO VCC1 D2 4 GND1 5 BOOSTED V+ C3 0.01F R3* TERMINATING RESISTOR (ONE RESISTOR ON EACH END) MAX3480EA/EB VCC5 24 MAX845 MAX1487E MAX487E TWISTED PAIR TO OTHER TRANSCEIVERS 23 A ISO DI IN 22 21 9 20 ISO COM1 10 19 ISO DI DRV 11 18 12 17 ISO DE DRV 13 16 15 ISOLATION BARRIER SHIELD (OPTIONAL) R7* A 8 14 RL B ISO RO DRV 7 10 TWISTED PAIR TO OTHER TRANSCEIVERS SH R6* RL ISO DE IN R4* SHIELD (OPTIONAL) R5* ISO VCC2 R8 100 ISO COM2 NOTE: RESISTOR R8 PROTECTS THE MAX3480E FROM TRANSIENT CURRENTS BETWEEN SHIELD AND A AND B. ISO RO LED ISOLATION COMMON *SEE TABLE 1. LOGIC GROUND C4 270pF 4kV Figure 2. Typical Application Circuit 10 ______________________________________________________________________________________ 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces ISOLATION BARRIER A ISOLATION BARRIER +3.3V +3.3V DE R CL1 A VOD D DI R RDIFF VID RO R B B VOC R3 A CL2 B Figure 3. Driver DC Test Load Figure 4. Driver/Receiver Timing Test Circuit S1 500 ISO VCC1, ISO VCC2 OUTPUT UNDER TEST CL S2 Figure 5. Driver Timing Test Load _______________________________________________________Switching Waveforms VCC_ - 0.4V DI 0 VCC_ - 0.4V VCC_ - 0.4V 2 VCC_ - 0.4V 2 tPHL tPLH VCC_ - 0.4V 2 VCC_ - 0.4V 2 0 1/2 VO tZL tLZ A, B B VO VOL A 1/2 VO VO VDIFF 0 -VO DE 10% tR 2.3V OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH A, B VDIFF = VA - VB VOH - 0.5V 2.3V 90% 90% 10% tF VOL + 0.5V 0 tZH tHZ tSKEW = | tPLH - tPHL | Figure 6. Driver Propagation Delays and Transition Times Figure 7. Driver Enable and Disable Times ______________________________________________________________________________________ 11 MAX3480EA/MAX3480EB _________________________________________________________________Test Circuits MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces __Switching Waveforms (continued) The MAX3480EA/MAX3480EB withstand 1260VRMS (1 min) or 1560VRMS (1s). The isolated outputs of these devices meet all RS-485/RS-422 specifications. Boost Voltage The MAX3480EA/MAX3480EB require external diodes on the primary of the transformer to develop the boost voltage for the power oscillator. In normal operation, whenever one of the oscillator outputs (D1 and D2) goes low, the other goes to approximately double the supply voltage. Since the circuit is symmetrical, the two outputs can be combined with diodes, filtered, and used to power the oscillator itself. The diodes on the primary side may be any fast-switching, small-signal diodes, such as the 1N914, 1N4148, or CMPD2838. The nominal value of the primary filter capacitor C3 is 0.01F. VOH RO 1.5V VOL VB - VA tPHL VID -VID OUTPUT 0 1.5V tPLH 0 INPUT tSKD = |tPLH - tPHL| Figure 8. Receiver Propagation Delays Driver Output Protection Function Tables Table 2. Transmitting INPUTS OUTPUTS DE DI B A 1 1 0 1 1 0 1 0 0 X High Impedance High Impedance DE A-B OUTPUT ---- RO 0 +0.2V 0 Resistor R8 (Figures 1 and 2) provides additional protection by current limiting between the shield and the two signal wires. In the event that shielded cable is used and an external voltage or transient is inadvertently applied between the shield and the signal wires, the MAX3480EA/MAX3480EB can be damaged. Although unlikely, this condition can occur during installation. The MAX3480EA/MAX3480EB provide electrical isolation between logic ground and signal paths; they do not provide isolation from external shields and the signal paths. When in doubt, do not connect the shield. The MAX3480EA/MAX3480EB can be damaged if resistor R8 is shorted out. 0 -0.2V 1 Applications Information 0 Inputs open 0 The MAX3480EA/MAX3480EB provide extra protection against ESD. The MAX3480EA/MAX3480EB are intended for harsh environments where high-speed communication is important. These devices eliminate the need for transient suppressor diodes or the use of discrete protection components. The standard (non-E) MAX3480A/MAX3480B are recommended for applications where cost is critical. X = Don't care. Table 3. Receiving INPUTS 12 There are two mechanisms to prevent excessive output current and power dissipation caused by faults or by bus contention. A foldback current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range (see the Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature rises excessively. ______________________________________________________________________________________ 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces RD 1500 CHARGE-CURRENT LIMIT RESISTOR IP 100% 90% DISCHARGE RESISTANCE Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) AMPERES HIGHVOLTAGE DC SOURCE Cs 100pF STORAGE CAPACITOR DEVICE UNDER TEST 36.8% 10% 0 0 Figure 9. Human Body ESD Test Model 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 outputs and receiver inputs have extra protection against static electricity. Maxim's engineers 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 power-down. After an ESD event, Maxim's MAX3480EA/MAX3480EB keep working without latchup. An isolation capacitor of 270pF 4kV should be placed between ISO COM and logic ground for optimal performance against an ESD pulse with respect to logic ground. ESD protection can be tested in various ways; the transmitter outputs and receiver inputs of this product family are characterized for protection to 15kV using the Human Body Model. ESD Test Conditions The +15kV ESD test specifications apply only to the A, B, Y, and Z I/O pins. The test surge may be referenced to either the ISO COM or to the nonisolated GND (this presupposes that a bypass capacitor is installed between VCC2 and the nonisolated GND). Human Body Model Figure 9 shows the Human Body Model, and Figure 10 shows the current waveform it generates when discharged into a low impedance. This model consists of a tRL TIME tDL CURRENT WAVEFORM Figure 10. Human Body Model Current Waveform 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a 1.5k resistor. Machine Model The Machine Model for ESD tests all pins using a 200pF storage capacitor and zero discharge resistance. Its objective is to simulate the stress caused by contact that occurs with handling and assembly during manufacturing. Of course, all pins require this protection during manufacturing--not just inputs and outputs. Therefore, after PC board assembly, the Machine Model is less relevant to l/O ports. The MAX3480EA/MAX3480EB are designed for bidirectional data communications on multipoint bus-transmission lines. Figure 11 shows a typical network application circuit. To minimize reflections, terminate the line at both ends with its characteristic impedance, and keep stub lengths off the main line as short as possible. The slewrate-limited MAX3480EB is more tolerant of imperfect termination and stubs off the main line. The MAX3480EA/MAX3480EB are specified and characterized using the resistor values shown in Table 1. Altering the recommended values can degrade performance. The DI and DE inputs are the cathodes of LEDs whose anodes are connected to VCC. These points are best driven by a +3.3V CMOS-logic gate with a series resistor to limit the current. The resistor values shown in Table 1 are recommended when the 74HC240 gate or equivalent is used. DI and DE are intended to be ______________________________________________________________________________________ 13 MAX3480EA/MAX3480EB RC 1M MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces closely represent those of discrete optocouplers, rather than the more robust characteristics of monolithic silicon ICs. The reliability testing programs for these multicomponent devices may be viewed on the Maxim website (www.maxim-ic.com) under Technical Support, Technical Reference, Multichip Products. driven through a series current-limiting resistor. Directly grounding these pins destroys the device. Reliability These products contain transformers, optocouplers, and capacitors, in addition to several monolithic ICs and diodes. As such, the reliability expectations more Table 4. Maxim's 15kV ESD-Protected Isolated RS-485 Product Family PART NO. OF Tx/Rx GUARANTEED DATA RATE (Mbps) FULL/HALF DUPLEX SLEW-RATE LIMITED NO. OF Tx/Rx ON BUS SUPPLY VOLTAGE (V) MAX1480EA 1/1 2.50 Half No 128 5.0 MAX1480EC 1/1 0.25 Half Yes 128 5.0 MAX1490EA 1/1 2.50 Full No 32 5.0 MAX1490EB 1/1 0.25 Full Yes 32 5.0 MAX3480EA 1/1 2.50 Half No 128 3.3 MAX3480EB 1/1 0.25 Half Yes 128 3.3 14 ______________________________________________________________________________________ 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces MAX3480EA/MAX3480EB TERMINATING RESISTOR (ONE RESISTOR ON EACH END) B D 120 DE A A B A B DI RO R RE R RE RE R D RO DE D DI RO DE VIN DI VCC1 +3.0V TO +3.6V C1 22F 6V C2 0.1F D1, D2 1N914 VCC2 D1 D2 BOOSTED V+ 74HC240 DI DE 2 17 18 3 4 16 6 14 8 12 15 DRIVER INPUT R1* DI VCC4 5 R2* DE 7 GND2 20 RO RO 9 11 28 AC1 (MAKE NO CONNECTION) 2 27 AC2 (MAKE NO CONNECTION) 3 26 ISO VCC1 4 25 B 24 MAX1487E MAX487E MAX845 RECEIVER OUTPUT R3* VCC5 10 LOGIC GROUND ISO DE IN 21 9 20 ISO COM1 10 19 ISO DI DRV 11 18 ISO VCC2 12 17 ISO DE DRV 13 16 14 B R7* A 23 A 8 15 ISOLATION BARRIER *SEE TABLE 1. ISO RO DRV 22 ISO DI IN SD 7 VCC3 DRIVER ENABLE 13 1 GND1 5 FS 6 C3 0.01F TERMINATING RESISTOR (ONE RESISTOR ON EACH END) MAX3480EA/EB R6* 120 SH SHIELD (OPTIONAL) R4* R5* R8 100 ISO COM2 ISO RO LED ISOLATION COMMON NOTE: RESISTOR R8 PROTECTS THE MAX3480E FROM TRANSIENT CURRENTS BETWEEN SHIELD AND A AND B. C4 270pF 4kV Figure 11. Typical RS-485/RS-422 Network ______________________________________________________________________________________ 15 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) D1 N DIM A A1 A2 A3 B B1 C D1 E E1 e eA eB L 1 TOP VIEW E D A E1 A3 A1 A2 e B1 B FRONT VIEW MILLIMETERS MAX MIN 5.08 0.39 3.18 4.45 1.40 2.03 0.41 0.51 1.14 1.65 0.21 0.30 0.13 0.22 15.24 15.87 13.34 14.61 2.54 BSC 15.24 BSC 3.05 17.78 3.81 VARIATIONS: INCHES 0-15 L INCHES MAX MIN 0.200 0.015 0.125 0.175 0.055 0.080 0.016 0.020 0.045 0.065 0.008 0.012 0.005 0.009 0.600 0.625 0.525 0.575 0.100 BSC 0.600 BSC 0.700 0.150 0.120 PDIPW.EPS MAX3480EA/MAX3480EB 15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces C eA eB MILLIMETERS DIM D MIN 1.230 MAX 1.270 MIN 31.24 MAX 32.26 N MS011 24 AA D D 1.430 2.025 1.470 2.075 36.32 51.44 37.34 52.71 28 40 AB AC SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, .600" PDIP APPROVAL DOCUMENT CONTROL NO. 21-0044 REV. B 1 1 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. 16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX3480EACPI+ MAX3480EAEPI+ MAX3480EBCPI+ MAX3480EBEPI+