19-1940; Rev 0; 4/01 ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces ____________________________Features The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB are complete, electrically isolated, RS-485/RS-422 data communications interface solutions in a hybrid microcircuit. The RS-485/RS-422 I/O pins are protected against ±15kV electrostatic discharge (ESD) shocks, without latchup. Transceivers, optocouplers, and a transformer provide a complete interface in a standard DIP package. A single +5V supply on the logic side powers both sides of the interface. ♦ Isolated Data Interface, Guaranteed to 1260VRMS (1min) ♦ ±15kV ESD Protection on I/O Pins ♦ Slew-Rate Limited for Errorless Data Transmission (MAX1480EC/MAX1490EB) ♦ High-Speed, Isolated, 2.5Mbps RS-485/RS-422 Interface (MAX1480EA/MAX1490EA) ♦ Full-Duplex Data Communication (MAX1490EA/MAX1490EB) ♦ Single +5V Supply ♦ Current Limiting and Thermal Shutdown for Driver Overload Protection ♦ Standard 0.6in DIP Packages 28-Pin DIP (MAX1480EA/MAX1480EC) 24-Pin DIP (MAX1490EA/MAX1490EB) The MAX1480EC/MAX1490EB feature 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 MAX1480EA/MAX1490EA driver slew rate is not limited, allowing transmission rates up to 2.5Mbps. The MAX1480EA/MAX1480EC are designed for half-duplex communication, while the MAX1490EA/MAX1490EB feature full-duplex communication. Drivers are short-circuit current limited and protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a highimpedance state. The receiver input has a fail-safe feature that guarantees a known output (RO low for the MAX1480EA/MAX1480EC, RO high for the MAX1490EA/ MAX1490EB) if the input is open circuit. The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB withstand 1260VRMS (1min) or 1520VRMS (1s). Their isolated outputs meet all RS-485/RS-422 specifications. The MAX1480EA/MAX1480EC are available in a 28-pin DIP package, and the MAX1490EA/MAX1490EB are available in a 24-pin DIP package. _______________Ordering Information PART† TEMP. RANGE MAX1480EACPI MAX1480EAEPI PIN-PACKAGE 0°C to +70°C 28 Wide Plastic DIP* -40°C to +85°C 28 Wide Plastic DIP* Ordering Information continued at end of data sheet. † Data rate for A parts is up to 2.5Mbps. Data rate for C parts is up to 250kbps. *See Reliability section at end of data sheet. Pin Configurations TOP VIEW 1 24 AC1 ________________________Applications VCC2 2 23 AC2 D1 3 22 ISO VCC1 D2 4 21 ISO RO DRV GND1 5 20 A 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 FS 6 MAX488E MAX490E VCC1 MAX845E . 19 B 7 18 Z VCC3 8 17 Y SD MAX1490EA/ MAX1490EB 9 16 ISO COM1 VCC4 10 15 ISO DI DRV DI 14 ISO VCC2 RO 11 13 ISO RO LED GND2 12 ISOLATION BARRIER DIP Selector Guide appears at end of data sheet. Pin Configurations continued at end of data sheet. ________________________________________________________________ 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 MAX1480E/MAX1490E _________________General Description MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces ABSOLUTE MAXIMUM RATINGS With Respect to GND_ Supply Voltage (VCC_)..........................................-0.3V to +6V Control Input Voltage (SD, FS)..............-0.3V to (VCC_ + 0.3V) Receiver Output Voltage (RO, RO).......-0.3V to (VCC_ + 0.3V) Output Switch Voltage (D1, D2).......................................+12V 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, Y, Z) ......................-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 = +70°C) 24-Pin Plastic DIP (derate 8.7mW°C above +70°C) ....696mW 28-Pin Plastic DIP (derate 9.09mW/°C above +70°C) .727mW Operating Temperature Ranges MAX1480E_CPI/MAX1490E_CPI ........................0°C to +70°C MAX1480E_EPI/MAX1490E_EPI ......................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VCC_ = +5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = +5V and TA = +25°C.) (Notes 1, 2) PARAMETER Switch Frequency SYMBOL CONDITIONS TYP VFS = 0 535 fSWH FS = VCC_ or open 725 85 145 55 120 130 180 65 130 MAX1480EA, DE´ = VCC_ or open Operating Supply Current MIN fSWL ICC MAX1480EC, DE´ = VCC_ or open MAX1490EA MAX1490EB Shutdown Supply Current (Note 3) ISHDN SD = VCC_ Shutdown Input Threshold VSDH VSDL High Low RL = ∞ RL = 54Ω RL = ∞ RL = 54Ω RL = ∞ RL = 54Ω RL = ∞ RL = 54Ω FS Input Pullup Current High Low FS low FS Input Leakage Current FS high Input High Voltage VIH DE´, DI´, Figures 1 and 2 Input Low Voltage VIL DE´, DI´, Figures 1 and 2 180 µA 0.8 50 10 1260 TA = +25°C, VISO = 50VDC 100 Isolation Capacitance CISO TA = +25°C, f = 1MHz Differential Driver Output (No Load) VOD1 Differential Driver Output (with Load) VOD2 V VRMS 10,000 MΩ 10 pF 8 R = 50Ω (RS-422) R = 27Ω (RS-485), Figure 4 µA V 0.4 TA = +25°C, 1min (Note 4) V pA VCC - 0.4 VISO V pA 2.4 RISO mA 125 0.8 Isolation Resistance mA 120 2.4 Isolation Voltage 2 120 10 VFSH VFSL UNITS kHz 0.2 Shutdown Input Leakage Current FS Input Threshold MAX 2 1.5 _______________________________________________________________________________________ 5 V V ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces (VCC_ = +5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = +5V and TA = +25°C.) (Notes 1, 2) PARAMETER SYMBOL Change in Magnitude of Driver Output Voltage for Complementary Output States ∆VOD Driver Common-Mode Output VOC CONDITIONS ISO IIN Receiver Differential Threshold 0.3 Common mode 0.3 DE´ = 0, VCC_ = 0 or +5.5V RIN -7V ≤ VCM ≤ +12V VTH -7V ≤ VCM ≤ +12V UNITS V 4 MAX1490EA/ MAX1490EB 1.0 MAX1480EA/ MAX1480EC 0.25 MAX1490EA/ MAX1490EB 0.8 MAX1480EA/ MAX1480EC 0.2 48 (MAX1490E_) 12 kΩ -0.2 ∆VTH VCM = 0 Receiver Output Low Voltage VOL Using resistor values listed in Tables 1 and 2 IOH VOUT = 5.5V V mA (MAX1480E_) Receiver Input Hysteresis Receiver Output High Current MAX Differential R = 27Ω or 50Ω, Figure 4 VIN = -7V Receiver Input Resistance TYP R = 27Ω or 50Ω, Figure 4 VIN = +12V Input Current (A, B) MIN 0.2 70 V mV 0.4 250 V µA Driver Short-Circuit Current ISO IOSD -7V ≤ VO ≤ 12V (Note 5) 100 mA ESD Protection ISO IOSD A, B, Y, and Z pins, tested using Human Body Model, Figures 1 and 2 ±15 kV SWITCHING CHARACTERISTICS—MAX1480EA/MAX1490EA (VCC_ = +5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = +5V and TA = +25°C.) PARAMETER Driver Input to Output Propagation Delay SYMBOL tPLH tPHL TYP MAX Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF CONDITIONS MIN 90 275 60 275 UNITS ns Driver Output Skew tSKEW Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF 30 100 ns Driver Rise or Fall Time tR, tF Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF 15 50 ns Driver Enable to Output High (MAX1480EA Only) tZH Figures 6 and 8, CL = 100pF, S2 closed 1.0 1.8 µs Driver Enable to Output Low (MAX1480EA Only) tZL Figures 6 and 8, CL = 100pF, S1 closed 1.0 1.8 µs Driver Disable Time from Low (MAX1480EA Only) tLZ Figures 6 and 8, CL = 15pF, S1 closed 0.5 1.8 µs Driver Disable Time from High (MAX1480EA Only) tHZ Figures 6 and 8, CL = 15pF, S2 closed 0.5 1.8 µs Receiver Input to Output Propagation Delay tPLH tPHL Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF 120 225 90 225 ns _______________________________________________________________________________________ 3 MAX1480E/MAX1490E ELECTRICAL CHARACTERISTICS (continued) MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces SWITCHING CHARACTERISTICS—MAX1480EA/MAX1490EA (continued) (VCC_ = +5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = +5V and TA = +25°C.) PARAMETER |tPLH - tPHL| Differential Receiver Skew Maximum Data Rate Time to Shutdown Shutdown to Driver Output High Shutdown to Driver Output Low SYMBOL CONDITIONS tSKD Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF fMAX tSHDN tSKEW, tSKD, tPHL ≤ 25% of data period tZH(SHDN) tZH(SHDN) Figures 6 and 9, CL = 100pF, S2 closed Figures 6 and 9, CL = 100pF, S1 closed MIN TYP MAX UNITS 30 150 ns 15 15 Mbps µs µs µs 2.5 100 3 3 SWITCHING CHARACTERISTICS—MAX1480EC/MAX1490EB (VCC_ = +5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS TYP MAX tPLH tPHL MIN 1.4 1.1 300 3.0 3.0 1200 UNITS Driver Output Skew tSKEW Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF Driver Rise or Fall Time tR, tF Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF 1.0 2.0 µs Driver Input to Output Propagation Delay µs ns Driver Enable to Output High (MAX1480EC Only) tZH Figures 6 and 8, CL = 100pF, S2 closed 1.4 4.5 µs Driver Enable to Output Low (MAX1480EC Only) tZL Figures 6 and 8, CL = 100pF, S1 closed 1.4 4.5 µs Driver Disable Time from Low (MAX1480EC Only) tLZ Figures 6 and 8, CL = 15pF, S1 closed 2.0 4.5 µs Driver Disable Time from High (MAX1480EC Only) tHZ Figures 6 and 8, CL = 15pF, S2 closed 1.7 4.5 µs Receiver Input to Output Propagation Delay tPLH tPHL Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF 0.9 1.1 3.0 3.0 µs |tPLH - tPHL| Differential Receiver Skew tSKD Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF 200 Maximum Data Rate fMAX tSKEW, tSKD ≤ 25% of data period Time to Shutdown tSHDN ns 160 kbps 100 µs Shutdown to Driver Output High tZH(SHDN) Figures 6 and 9, CL = 100pF, S2 closed 3 15 µs Shutdown to Driver Output Low tZL(SHDN) Figures 6 and 9, CL = 100pF, S1 closed 3 15 µs Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to logicside ground (GND_), unless otherwise specified. Note 2: For DE´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480EA/ MAX1480EC, Figure 2 for MAX1490EA/MAX1490EB). Note 3: Shutdown supply current is the current at VCC1 and VCC2 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, e.g., between pins 1–14 and pins 15–28 on the 28-pin package. Note 5: Applies to peak current (see Typical Operating Characteristics). Although the MAX1480EA/MAX1480EC and MAX1490EA/MAX1490EB provide electrical isolation between logic ground and signal paths, they do not provide isolation between external shields and the signal paths (see Isolated Common Connection section). 4 _______________________________________________________________________________________ ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces 50 40 30 -20 -15 -10 20 10 0 -40 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 20 40 60 80 OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE 0.2 120 100 80 60 -80 -70 -60 -50 -40 -30 40 -20 0.1 20 -10 0 0 -20 0 20 40 60 0 0 80 1 2 3 4 5 6 7 8 9 10 11 12 TEMPERATURE (°C) OUTPUT LOW VOLTAGE (V) DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE 70 60 50 40 30 20 10 3.0 DI´ = HIGH OR OPEN RL = 54Ω 2.9 2.8 2.7 2.6 2.5 2.4 2.3 2.2 DIFFERENTIAL OUTPUT VOLTAGE (V) 0.40 SD = VCC_, DI´ = VCC_ DE´= VCC_(MAX1480EC ONLY) MEASURED AT VCC1 AND VCC2 0.35 0.30 0.25 0.20 0.15 0.10 0 2.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SHUTDOWN CURRENT vs. TEMPERATURE 0.05 2.1 0 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 OUTPUT HIGH VOLTAGE (V) MAX1480E/90E TOC08 DI´ = HIGH OR OPEN DIFFERENTIAL OUTPUT VOLTAGE (V) 80 MAX1480E/90E TOC06 MAX1480E/90E TOC05 140 -90 MAX1480E/90E TOC09 0.3 160 -100 OUTPUT CURRENT (mA) 0.4 180 OUTPUT CURRENT (mA) 0.5 0 -20 RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE MAX1480E/90E TOC07 OUTPUT LOW VOLTAGE (V) 3.50 TEMPERATURE (°C) 0.6 -40 OUTPUT CURRENT (mA) 3.75 OUTPUT HIGH VOLTAGE (V) MEASURED AT ISO RO DRV IRO = 8mA 0.7 4.00 OUTPUT LOW VOLTAGE (V) MAX1480E/90E TOC04 0.8 4.25 3.00 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 4.50 3.25 0 0 MEASURED AT ISO RO DRV IRO = 8mA 4.75 -5 MAX1480E/90E TOC03 -25 5.00 OUTPUT HIGH VOLTAGE (V) 60 MEASURED AT ISO RO DRV SHUTDOWN CURRENT (µA) OUTPUT CURRENT (mA) 70 -30 MAX1480E/90E TOC02 MEASURED AT ISO RO DRV OUTPUT CURRENT (mA) 80 RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE MAX1480E/90E TOC01 OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE -40 -20 0 20 40 TEMPERATURE (°C) 60 80 -40 -20 0 20 40 60 80 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX1480E/MAX1490E __________________________________________Typical Operating Characteristics (VCC_ = +5V, VFS = VCC_, Figures 1 and 2, TA = +25°C, unless otherwise noted.) ____________________________Typical Operating Characteristics (continued) (VCC_ = +5V, VFS = VCC_, Figures 1 and 2, TA = +25°C, unless otherwise noted.) 100 DE´ = VCC RL = ∞ 80 60 40 VCC = +5.5V VCC = +4.5V 20 100 VCC = +5V 90 VCC = +4.5V 80 DE´ = VCC 70 60 VCC = +5.5V 50 VCC = +5V VCC = +5V 40 0 VCC = +4.5V 20 -20 0 20 40 60 80 RL = 54Ω VCC = +5.5V 180 VCC = +5V 160 VCC = +4.5V 140 VCC = +5.5V 120 VCC = +5V RL = ∞ 100 30 -40 RL = ∞ 200 SUPPLY CURRENT (mA) VCC = +4.5V RL = 54Ω VCC = +5.5V 110 MAX1490EA SUPPLY CURRENT vs. TEMPERATURE MAX1480E/90E T0C11 VCC = +5V 120 120 SUPPLY CURRENT (mA) RL = 54Ω VCC = +5.5V 140 MAX1480E/90E TOC10 160 MAX1480EC SUPPLY CURRENT vs. TEMPERATURE -40 -20 TEMPERATURE (°C) 0 20 40 60 VCC = +4.5V 80 80 -40 -20 TEMPERATURE (°C) 0 20 40 60 80 TEMPERATURE (°C) 150 VCC = +5.5V 140 VCC = +5V 130 SUPPLY CURRENT (mA) MAX1480E/90E TOC13 MAX1490EB SUPPLY CURRENT vs. TEMPERATURE VCC = +4.5V 120 RL = 54Ω 110 100 90 80 VCC = +5V VCC = +5.5V RL = ∞ 70 60 VCC = +4.5V 50 -40 -20 0 20 40 60 80 TEMPERATURE (°C) MAX1480EA/MAX1490EA RECEIVER tPLH MAX1480EA/MAX1490EA RECEIVER tPHL MAX1480E/90E toc15 MAX1480E/90E toc14 RECEIVER INPUT A 1V/div RECEIVER INPUT B 1V/div RECEIVER INPUT B 1V/div RECEIVER INPUT A 1V/div RO 2V/div RO 2V/div 20ns/div 20ns/div VCC_ = 5.0V, DE´= VCC_ DI´ = 0V TO 5V AT 1 25MHz 6 VCC_ = 5.0V, DE´= VCC_ _______________________________________________________________________________________ MAX1480E/90E TOC12 MAX1480EA SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT (mA) MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces (VCC_ = +5V, VFS = VCC_, VDI´ = 0, DE´ toggled 0 to 5V at 5kHz, Figures 1 and 2, TA = +25°C, unless otherwise noted.) MAX1480EC/MAX1490EB RECEIVER tPHL MAX1480EC/MAX1490EB RECEIVER tPLH MAX1480E/90E toc16 MAX1480E/90E toc17 RECEIVER INPUT A 1V/div RECEIVER INPUT A 1V/div RECEIVER INPUT B 1V/div RECEIVER INPUT B 1V/div RO 2V/div RO 2V/div 200ns/div 500ns/div VCC = 5 0V DE´= VCC VCC = 5 0V DE´= VCC MAX1480EC DRIVER DISABLE TIME MAX1480E/90E TOC18 MAX1480E/90E TOC19 MAX1480EC DRIVER ENABLE TIME DRIVER OUTPUT B 2V/div DRIVER OUTPUT B 2V/div DE´ 2V/div DE´ 2V/div 500ns/div 500ns/div VCC = 5.0V, DI´ = 0V VCC = 5.0V, DI´= 0V MAX1480E/90E TOC20 MAX1480EA/MAX1490EA POWER-UP DELAY TO DRIVER OUTPUTS VALID DRIVER OUTPUT B (Z FOR MAX1490) 2V/div SD 2V/div 1µs/div VDI´ = 0 VSD = 5V TO 0 AT 1kHz _______________________________________________________________________________________ 7 MAX1480E/MAX1490E _____________________________Typical Operating Characteristics (continued) MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces ________________________________________________________________Pin Description PIN 8 MAX1480EA/ MAX1480EC MAX1490EA/ MAX1490EB NAME FUNCTION 1, 2, 8, 10 3, 4 5 1, 2, 8, 10 3, 4 5 VCC1–VCC4 D1, D2 GND1 6 6 FS Frequency Select Input. If FS = VCC_ or is open, switch frequency is high; if FS = GND, switch frequency is low. For optimal performance and minimal supply current, connect FS to VCC_ or leave unconnected. 7 7 SD Shutdown Input. Ground for normal operation. When high, the power oscillator is disabled. 9 9 DI Driver Input. With DE´ high (MAX1480EA/MAX1480EC only), 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 a resistor (see Table 1 for MAX1480EA/MAX1480EC, Table 2 for MAX1490EA/MAX1490EB). Logic-Side (Nonisolated Side) +5V Supply Voltages Internal Connections. Leave these pins unconnected. Logic-Side Ground. Connect to GND2 (pin 12). 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 a resistor (Table 1). — 11 RO Receiver Output. If A > B by 200mV, RO is high; if A < B by 200mV, RO is low. Open collector; must have pullup to VCC (Table 2). 12 12 GND2 13 — RO 14 — VCC5 15 13 ISO RO LED 16 — ISO COM2 17 — ISO DE DRV 18 14 ISO VCC2 Logic-Side Ground. Connect to GND1 (pin 5). Receiver Output. If A > B by 200mV, RO is low; if A < B by 200mV, RO is high. Open collector; must have pullup to VCC (Table 1). Logic-Side (Nonisolated Side) +5V Supply Voltage Isolated Receiver Output LED. Internal LED anode in MAX1480EA/MAX1480EC and LED cathode in MAX1490EA/MAX1490EB. Connect to ISO RO DRV through a resistor (Table 1 for MAX1480EA/MAX1480EC; Table 2 for MAX1490EA/MAX1490EB). Isolated Common. Connect to ISO COM1 (pin 20). Isolated Driver-Enable Drive. 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 to ISO VCC_ and be connected to ISO DE IN for normal operation (Table 1). Isolated Supply Voltage. Connect to ISO VCC1 (pin 26 for MAX1480EA/ MAX1480EC, or pin 22 for MAX1490EA/MAX1490EB). 19 15 ISO DI DRV Isolated Driver-Input Drive. With DE´ high (MAX1480EA/MAX1480EC only), 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. Connect to ISO DI IN (on the MAX1480EA/MAX1480EC only) for normal operation. Open-collector output; connect a pullup resistor to ISO VCC_ (Table 1 for MAX1480EA/MAX1480EC, Table 2 for MAX1490EA/MAX1490EB). 20 16 ISO COM1 Isolated Common. For MAX1480EA/MAX1480EC, connect to ISO COM2 (pin 16) (Figures 1 and 2). _______________________________________________________________________________________ ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces PIN MAX1480EA/ MAX1480EC MAX1490EA/ MAX1490EB NAME — — — — 21 22 23 17 18 19 20 — — — Y Z B A ISO DE IN ISO DI IN A 24 21 ISO RO DRV 25 26 27, 28 — 22 23, 24 B ISO VCC1 AC2, AC1 FUNCTION Noninverting Driver Output Inverting Driver Output Inverting Receiver Input Noninverting Receiver Input Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation. Isolated Driver Input. Connect to ISO DI DRV for normal operation. Noninverting Driver Output and Noninverting Receiver Input Isolated Receiver-Output Drive. Connect to ISO RO LED through a resistor (see Table 1 for MAX1480EA/MAX1480EC, Table 2 for MAX1490EA/MAX1490EB). Inverting Driver Output and Inverting Receiver Input Isolated Supply Voltage Source Internal Connections. Leave these pins unconnected. Note: For DE´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480EA/ MAX1480EC, Figure 2 for MAX1490EA/MAX1490EB). Detailed Description The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB are complete, electrically isolated, RS-485/RS-422 datacommunications interface solutions. Transceivers, optocouplers, a power driver, and a transformer in one standard 28-pin DIP package (24-pin package for the MAX1490EA/MAX1490EB) provide a complete interface. Signals and power are internally transported across the isolation barrier (Figures 1, 2). 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 highspeed optocouplers. A single +5V supply on the logic side powers both sides of the interface. The MAX1480EA/MAX1480EC offer half-duplex communications while the MAX1490EA/MAX1490EB feature fullduplex communication. The functional input/output relationships are shown in Tables 3 through 6. The MAX1480EC/MAX1490EB feature 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 MAX1480EA/MAX1490EA driver slew rate is not limited, allowing transmission rates up to 2.5Mbps. The MAX1480EC/MAX1490EB shutdown feature reduces supply current to as low as 0.2µA by using the SD pin (see Low-Power Shutdown Mode section). 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 RO (logic-low RO) output if the input is open circuit. On the MAX1480EA/MAX1480EC, the driver outputs are enabled by bringing DE´ high. Driver-enable time is typically 1.0µs. Allow time for the devices to be enabled before sending data (see Typical Operating Characteristics). When enabled, driver outputs function as line drivers. Driver outputs are high impedance when DE´ is low. When outputs are high impedance, they function as line receivers. The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB withstand 1260VRMS (1min) or 1520VRMS (1s). The logic inputs can be driven from TTL/CMOS logic with a series resistor, and the received data output can directly drive TTL or CMOS-logic families with only a resistive pullup. Low-Power Shutdown Mode The SD pin shuts down the oscillator on the internal power driver. With the primary side in shutdown, no power is transferred across the isolation barrier. The DI and DE optocouplers, however, still consume current if the drive signals on the nonsolated side are low. Therefore, leave DI´ and DE´ high or floating when in shutdown mode. Under these conditions, the MAX1480EC/MAX1490EB supply current is reduced to as low as 0.2µA. _______________________________________________________________________________________ 9 MAX1480E/MAX1490E ___________________________________________________Pin Description (continued) MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces VCC3 ISO VCC1 D1 MAX845E Q OSC 1.07MHz/ 1.45MHz FS MAX1480EA: MAX1487E MAX1480EC: MAX487E N T F/F B ISO DI IN D D2 Q N A ISO DE IN ISO RO DRV R RE GND1 SD ISO COM1 EXTERNAL RS-485/RS-422 WIRING VIN +5V C1 22µF C2 0.1µF VCC1 1 28 AC1 (MAKE NO CONNECTION) VCC2 2 27 AC2 (MAKE NO CONNECTION) D2 4 GND1 5 FS 6 SD DI VCC3 R1* DRIVER INPUT DI´ DE R2* DRIVER ENABLE DE´ R3* RECEIVER OUTPUT DI VCC4 DE GND2 VCC5 *SEE TABLE 1. 24 MAX845E MAX1487E MAX487E LOGIC GROUND SHIELD (OPTIONAL) A TWISTED PAIR TO OTHER TRANSCEIVERS 23 A 7 8 21 9 20 ISO COM1 19 ISO DI DRV 11 18 ISO VCC2 12 17 ISO DE DRV 16 15 SH R6* RL ISO DE IN 10 14 RL B ISO RO DRV 22 ISO DI IN RO 13 RO TWISTED PAIR TO OTHER TRANSCEIVERS 26 ISO VCC1 B 25 D1 3 74HC86 OR EQUIVALENT TERMINATING RESISTOR (ONE RESISTOR ON EACH END) MAX1480EA MAX1480EC R4* SHIELD (OPTIONAL) R5* R7 100Ω ISO COM2 NOTE: RESISTOR R7 PROTECTS THE MAX1480EA FROM TRANSIENT CURRENTS BETWEEN SHIELD AND TRANSMISSION LINES. ISO RO LED ISOLATION BARRIER ISOLATED COMMON 270pF 4kV Figure 1. MAX1480EA/MAX1480EC Detailed Block Diagram and Application Circuit Table 1. Pullup and LED Drive Resistors for Figure 1 R1 (Ω) R2 (Ω) R3 (Ω) R4 (Ω) R5 (Ω) R6 (Ω) MAX1480EA PART 200 200 1000 4300 1000 200 MAX1480EC 200 200 3000 3000 3000 200 The high-speed optocouplers on the MAX1480EA/ MAX1480EC/MAX1490EA consume an additional 10mA through VCC5 (VCC4 for the MAX1490EA). Therefore, to completely shut down these devices, use an external Pchannel MOSFET as shown in Figure 3. In normal operation, SD is low, turning the MOSFET on and thereby providing power to all the VCC pins. When SD is pulled high, the power oscillator is disabled and the switch is turned off, disconnecting power from the DI and DE opto10 couplers. In normal operating mode, the switch carries only the optocoupler currents, so an on-resistance of several ohms does not significantly degrade efficiency. ______________________________________________________________________________________ ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces MAX1480E/MAX1490E VCC3 D1 MAX845 Q OSC 1.07MHz/ 1.45MHz FS N T F/F A R D2 Q ISO RO DRV B ISO DI DRV N MAX1490EA: MAX490E MAX1490EB: MAX488E Z D SD MAX1490EA/ MAX1490EB VIN +5V VCC1 C1 22µF C2 0.1µF VCC2 D1 24 AC1 (MAKE NO CONNECTION) 2 23 AC2 (MAKE NO CONNECTION) 3 22 ISO VCC1 R1* DI´ RECEIVER OUTPUT RO R2* MAX488E MAX490E MAX845 SD 7 DRIVER INPUT TERMINATING RESISTOR (ONE RESISTOR ON EACH END) TWISTED PAIR TO OTHER TRANSCEIVERS 21 ISO RO DRV 5 FS 6 74HC86 OR EQUIVALENT EXTERNAL RS-485/RS-422 WIRING 1 D2 4 GND1 DI Y GND1 VCC3 8 RL 20 A A 19 B B 18 Z Z 17 Y 16 ISO COM1 VCC4 10 15 ISO DI DRV R4* 14 ISO VCC2 TWISTED PAIR TO OTHER TRANSCEIVERS RL SH1 SHIELD (OPTIONAL) SH2 R3* ISOLATION BARRIER ISOLATED COMMON *SEE TABLE 2. LOGIC GROUND RL R6, 100Ω 13 ISO RO LED GND2 12 SHIELD (OPTIONAL) Y R5, 100Ω DI 9 R0 11 RL NOTE: RESISTORS R5 AND R6 PROTECT THE MAX1490EA/MAX1490EB FROM TRANSIENT CURRENTS BETWEEN SHIELD AND TRANSMISSION LINES. 270 pF 4kV Figure 2. MAX1490EA/MAX1490EB Detailed Block Diagram and Typical Application Circuit Table 2. Pullup and LED Drive Resistors for Figure 2 R1 (Ω) R2 (Ω) R3 (Ω) R4 (Ω) MAX1490EA PART 200 1000 330 1000 MAX1490EB 200 3000 330 3000 MAX1480EC/MAX1490EB: Reduced EMI and Reflections The MAX1480EC/MAX1490EB are slew-rate-limited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 11 shows both the driver output waveform of a MAX1480EA/ MAX1490EA transmitting a 150kHz signal and the Fourier analysis of that waveform. High-frequency harmonics with large amplitudes are evident. Figure 12 shows the same information for the slew-rate-limited MAX1480EC/MAX1490EB transmitting the same signal. The high-frequency harmonics have much lower amplitudes, and therefore the potential for EMI is significantly reduced. Driver Output Protection 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 cir- ______________________________________________________________________________________ 11 MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces MAX1480EA VIN +5V Si9433DY VCC1 1 28 AC1 VCC2 2 27 AC2 D1 3 26 ISO VCC1 D2 4 25 B 24 ISO RO DRV GND1 5 P FS 6 SHUTDOWN R1 DI´ R2 MAX845 MAX1487E 22 ISO DI IN VCC3 8 21 ISO DE IN DI 9 20 ISO COM1 VCC4 10 19 ISO DI DRV DE 11 DE´ R3 18 ISO VCC2 GND2 12 17 ISO DE DRV RO 13 RO 23 A SD 7 VCC5 16 ISO COM2 15 ISO RO LED 14 ISOLATION BARRIER GND Figure 3. MAX1480EA Low-Power Shutdown Mode Test Circuits ISOLATION BARRIER ISOLATION BARRIER ISOLATION BARRIER (DE´) D DI´ VOD R Figure 4. Driver DC Test Load 12 ( ) ARE FOR THE MAX1480EA/MAX1480EC. CL1 R VOC D RDIFF VID CL2 R RO (RO)* * OPTOCOUPLER OUTPUTS. SEE FIGURES 1 AND 2 FOR DETAILED BLOCK DIAGRAM AND TYPICAL APPLICATION CIRCUIT. Figure 5. Driver/Receiver Timing Test Circuit ______________________________________________________________________________________ ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces ISO VCC_ S1 500Ω OUTPUT UNDER TEST CL S2 Figure 6. Driver Timing Test Load Switching Waveforms VCC_ - 0.4V DI´ VCC_ - 0.4V 2 VCC_ - 0.4V 2 0 tPLH DE´ tPHL 0 1/2 VO VCC_ - 0.4V 2 VCC_ - 0.4V 2 tLZ tZL B A, B VO A 2.3V OUTPUT NORMALLY LOW VOL 1/2 VO VO VDIFF 0 -VO VCC_ -0.4V 10% VDIFF = V (A) - V (B) 90% tR OUTPUT NORMALLY HIGH A, B 90% VOL + 0.5V VOH - 0.5V 2.3V 10% 0 tF tZH tHZ tSKEW = tPLH - tPHL Figure 7. Driver Propagation Delays and Transition Times Figure 8. Driver Enable and Disable Times INPUT VID 2.4V SD 0.8V 1.6V 1.6V tZL(SHDN) -VID VA - V B MAX1490EA/MAX1490EB OUTPUT tSHDN A, B VOL 0 0 2.3V OUTPUT NORMALLY LOW VOL + 0.5V RO VOH VOL 1.5V tPLH 1.5V tPHL OUTPUT NORMALLY HIGH A, B VOH - 0.5V 2.3V 0 tZH(SHDN) Figure 9. Times to/from Shutdown tSHDN RO VOH VOL 1.5V MAX1480EA/MAX1480EC 1.5V OUTPUT tPHL tSKEW = tPLH - tPHL tPLH Figure 10. Receiver Propagation Delays ______________________________________________________________________________________ 13 MAX1480E/MAX1490E ____________________________________________________Test Circuits (continued) MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces cuits over the entire common-mode range (see Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-im pedance state if the die temperature rises excessively. _____________________Function Tables Half-Duplex Devices (MAX1480EA/MAX1480EC) Propagation Delay Skew Propagation delay skew is the difference between the low-to-high and high-to-low propagation delay. Small driver/receiver skew times help reduce EMI and reflections by maintaining balanced differential signals. Table 3. Transmitting INPUTS* OUTPUTS DE´ DI´ B 1 1 0 1 0 1 0 0 X High-Z High-Z A 1 X = Don’t care; High-Z = High impedance Table 4. Receiving INPUTS* 10dB/div 0 DE´ VA - VB OUTPUT (RO) 0 ≥ +0.2V 0 0 ≤ -0.2V 1 0 Open 0 5MHz Full-Duplex Devices (MAX1490EA/MAX1490EB) 500kHz/div Figure 11. Driver Output Waveform and FFT Plot of MAX1480EA/MAX1490EA Transmitting a 150kHz Signal Table 5. Transmitting INPUT* OUTPUTS (DI´) Z Y 1 0 1 0 1 0 * For DE´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480EA/ MAX1480EC, Figure 2 for MAX1490EA/MAX1490EB). 10dB/div Table 6. Receiving 0 5MHz 500kHz/div Figure 12. Driver Output Waveform and FFT Plot of MAX1480EC/ MAX1490EB Transmitting a 150kHz Signal 14 INPUT (VA - VB) OUTPUT (RO) ≥ +0.2V 1 ≤ -0.2V 0 Open 1 ______________________________________________________________________________________ ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces These E versions of the MAX1480EA/MAX1480EC/ 1490EA/MAX1490EB provide extra protection against ESD. The rugged MAX1480EA/MAX1480EC/MAX1490EA/ MAX1490EB 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) MAX1480A/MAX1480C/MAX1490A/MAX1490B are recommended for applications where cost is critical. ±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 powered down. After an ESD event, Maxim’s MAX1480EA/MAX1480EC/MAX1490EA/ MAX1490EB keep working without latchup. An isolation capacitor of 270pF 4kV should be placed between ISO COM and logic ground for optional 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 (Figures 1 and 2). R C 1MΩ CHARGE-CURRENT LIMIT RESISTOR R D 1500Ω Human Body Model Figure 13 shows the Human Body Model, and Figure 14 shows the current waveform it generates when discharged into 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. 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. All pins require this protection during manufacturing—not just inputs and outputs. Therefore, after PC board assembly, the Machine Model is less relevant to I/O ports. The MAX1480EA/MAX1480EC are designed for bidirectional data communications on multipoint bus-transmission lines. The MAX1490EA/MAX1490EB are designed for full-duplex bidirectional communications that are primarily point-to-point. Figures 15 and 16 show half-duplex and full-duplex typical network application circuits, respectively. 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 slew-rate-limited MAX1480EC/MAX1490EB are more tolerant of imperfect termination and stubs off the main line. Layout Considerations The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB pinouts enable optimal PC board layout by minimizing interconnect lengths and crossovers: • For maximum isolation, the “isolation barrier” should not be breached except by the MAX1480EA/ 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 13. Human Body ESD Test Model tRL TIME tDL CURRENT WAVEFORM Figure 14. Human Body Current Waveform ______________________________________________________________________________________ 15 MAX1480E/MAX1490E ___________Applications Information MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces TERMINATING RESISTOR (ONE RESISTOR ON EACH END) B DI D 120Ω DE A A A B B RO R 100Ω RE R RE R RE D D RO DE DI RO DE DI MAX1480EA/ MAX1480EC VIN +5V C1 22µF C2 0.1µF VCC1 1 28 AC1 (MAKE NO CONNECTION) VCC2 2 27 AC2 (MAKE NO CONNECTION) 26 ISO VCC1 D1 3 FS 6 SD 7 DI DE VCC3 DRIVER INPUT DRIVER ENABLE R1 R2 R3 RECEIVER OUTPUT RO DI VCC4 DE GND2 24 MAX845E MAX487E MAX1487E ISO RO DRV 23 A 22 ISO DI IN ISO DE IN 8 21 9 20 ISO COM1 10 19 ISO DI DRV 11 18 ISO VCC2 12 17 ISO DE DRV RO 13 VCC5 14 LOGIC GROUND B 25 B D2 4 GND1 5 74HC86 OR EQUIVALENT TERMINATING RESISTOR (ONE RESISTOR ON EACH END) 16 15 ISOLATION BARRIER A R6 120Ω SH R4 SHIELD (OPTIONAL) R5 R7 100Ω NOTE: RESISTOR R7 PROTECTS THE MAX1480EA/MAX1480EC FROM TRANSIENT CURRENTS BETWEEN SHIELD AND TRANSMISSION LINES. ISO COM2 ISO RO LED ISOLATED COMMON 270pF 4kV Figure 15. Typical Half-Duplex RS-485/RS-422 Network 16 ______________________________________________________________________________________ ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces C1 22µF C2 0.1µF VCC1 1 24 AC1 (MAKE NO CONNECTION) VCC2 2 23 AC2 (MAKE NO CONNECTION) D1 3 22 ISO VCC1 D2 4 21 ISO RO DRV FS 6 SD 7 74HC86 OR EQUIVALENT VCC3 R1 DI DRIVER INPUT DI´ R2 MAX488E MAX490E MAX845E GND1 5 8 RECEIVER OUTPUT A 19 B B 18 Z Z 17 Y Y 16 ISO COM1 VCC4 10 15 ISO DI DRV R4 13 ISO RO LED GND2 12 DI R RO SHIELD (OPTIONAL) 120Ω B 120Ω A SHIELD (OPTIONAL) R6, 100Ω R3 ISOLATED COMMON ISOLATION BARRIER LOGIC GROUND SH2 D Z R5, 100Ω SH1 14 ISO VCC2 RO 11 RO 120Ω 20 A DI 9 Y 120Ω NOTE: RESISTORS R5 AND R6 PROTECT THE MAX1490EA/MAX1490EB FROM TRANSIENT CURRENTS BETWEEN SHIELD AND TRANSMISSION LINES. 270pF 4kV Figure 16. Typical Full-Duplex RS-485/RS-422 Network MAX1480EC/MAX1490EA/MAX1490EB. Connections and components from one side should not be located near those of the other side. • A shield trace connected to the ground on each side of the barrier can help intercept capacitive currents that might otherwise couple into the signal path. In a double-sided or multilayer board, these shield traces should be present on all conductor layers. • Try to maximize the width of the isolation barrier wherever possible; a clear space of at least 0.25 inches between ground and isolated common is suggested. Pullup and LED Drive Resistors The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB are specified and characterized using the resistor values shown in Tables 1 and 2. Altering the recommended values can degrade performance. DI and DE are intended to be driven through a series current-limiting resistor. Directly grounding these pins destroys the device. The DI and DE (MAX1480EA/MAX1480EC only) inputs are the cathodes of LEDs whose anodes are connected to the supply. These points are best driven by a CMOSlogic gate with a series resistor to limit the current. The resistor values shown in Tables 1 and 2 are recommended when the 74HC86 gate or equivalent is used. These values may need to be adjusted if a driving gate with dissimilar series resistance is used. All pullup resistors are based on optocoupler specifications in order to optimize the devices’ data-transfer rates. Isolated Common Connection The isolated common may be completely floating with respect to the logic ground and the effective network ground. The receiver input resistors cause the isolated common voltage to go to the mean voltage of the receiver inputs. If using shielded cable, connect the isolated common to the shield through a 100Ω resistor. In the case of the MAX1490EA/MAX1490EB, each shield should have its own 100Ω resistor (Figures 1, 2, 15, and 16). Double-Isolated RS-485 Repeater The RS-422/RS-485 standard is specified for cable lengths up to 4000 feet. When approaching or exceeding the specified maximum cable length, a ground-potential difference of several tens of volts can easily develop. This difference can be either DC, AC, at power-line frequency, or any imaginable noise or impulse waveform. It is typically very low impedance so that if a connection between the two grounds is attempted, very large cur- ______________________________________________________________________________________ 17 MAX1480E/MAX1490E MAX1490EA/ MAX1490EB VIN +5V MAX1480E/MAX1490E ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces rents may flow. These currents are by their nature unstable and unpredictable. In addition, they may cause noise to be injected into sensitive instrumentation and, in severe cases, might actually cause physical damage to such equipment. Figure 17 shows a half-duplex (2-wire), bidirectional, party-line repeater system that prevents interference and/or damage from ground-potential differences. Two MAX1480EA/MAX1480EC isolated RS-485 transceivers are used to isolate each of the network segments from the electrical environment of the repeater. The MAX1480EA/MAX1480EC also regenerate bus signals that may have been degraded by line attenuation or dispersion. In the idle state, both transmitters are disabled, while all receivers in the system are enabled. If any device on the system has information for any other device, it starts sending its data onto the bus. Each data transmission on the bus retriggers the one-shot, keeping the sending transmitter enabled until there are no more transmissions. All receivers receive all data; if this is undesirable, the protocol must allow for an address field so receivers can ignore data not directed to them. Each node must refrain from transmitting when data already exists on the bus, and must resend data that is corrupted by the collisions that inevitably occur with a party-line system. With the repeater of Figure 17, there might be transmitters up to 8000 feet apart. That represents more than 8µs (assuming 1ns/foot of delay) in which two nodes could be transmitting simultaneously. The circuit in Figure 17 can be used either directly as shown, with the slew-rate-limited MAX1480EC, for data transfer rates up to 160kbps, or with the MAX1480EA for data rates up to 2.5Mbps (see Table 1 for pullup and LED resistor values when using the MAX1480EA). If dualport isolation is not needed, one of the MAX1480EC devices can be replaced by a MAX487E for 250kbps applications. Reliability These products contain transformers, optocouplers, and capacitors, in addition to several monolithic ICs and diodes. As such, the reliability expectations more 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. +5V +5V NETWORK SEGMENT B NETWORK SEGMENT A 2 8 10 14 A 23 B 25 2 8 10 14 3kΩ 13 1 26 3kΩ 3kΩ 200Ω 2 9 19 22 17 21 11 24 200Ω 200Ω 4 MAX1480EC 3 13 DRIVER ENABLE 200Ω A>B DRIVER ENABLE B>A 23 A 25 B 26 3kΩ 74HC04 MAX1480EC 9 3kΩ 19 22 17 21 11 3kΩ 24 200Ω 200Ω 15 15 5 7 12 5 7 12 +5V +5V 51kΩ 1000pF 16 15 2 B 7 14 Q 13 10 B Q 4 9 A CLR 3 6 Q 5 74HC123 74HC123 1 A 51kΩ 1000pF Q 12 CLR 11 Figure 17. Double-Isolated RS-485 Repeater 18 ______________________________________________________________________________________ ±15kV ESD-Protected, Isolated RS-485/RS-422 Data Interfaces Pin Configurations (continued) PART† TEMP. RANGE MAX1480ECCPI 0°C to +70°C 28 Wide Plastic DIP MAX1480ECEPI -40°C to +85°C 28 Wide Plastic DIP 0°C to +70°C 24 Wide Plastic DIP -40°C to +85°C 24 Wide Plastic DIP 0°C to +70°C 24 Wide Plastic DIP VCC1 1 24 Wide Plastic DIP VCC2 2 MAX1490EACPG MAX1490EAEPG MAX1490EBCPG MAX1490EBEPG -40°C to +85°C PIN-PACKAGE † Data rate for A parts is up to 2500kbps. Data rate for C parts is up to 250kbps. MAX1480EA/ MAX1480EC TOP VIEW 28 AC1 27 AC2 26 ISO VCC1 D1 3 25 B D2 4 GND1 5 FS 6 Selector Guide MAX845 MAX487E MAX1487E 23 A SD 7 22 ISO DI IN VCC3 8 21 ISO DE IN DI 9 20 ISO COM1 VCC4 10 19 ISO DI DRV PART HALF/ FULL DUPLEX DATA RATE (Mbps) SLEWRATE LIMITED MAX1480EA Half 2.5 No RO 13 MAX1480EC MAX1490EA MAX1490EB Half Full Full 0.25 2.5 0.25 Yes No Yes VCC5 14 This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board-level solder attach and rework. Maxim recommends the use of the solder profiles recommended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection Reflow processes. Preheating, per this standard, is required. Hand or wave soldering is not recommended. 24 ISO RO DRV 18 ISO VCC2 DE 11 17 ISO DE DRV GND2 12 16 ISO COM2 15 ISO RO LED ISOLATION BARRIER DIP 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___________________ 19 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX1480E/MAX1490E Ordering Information (continued)