MAX13410E_09

19-1058; Rev 1; 8/09 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control General Description The MAX13410E–MAX13415E are half-duplex RS-485-/RS422-compatible transceivers optimized for isolated applications. These devices feature an internal low-dropout regulator (LDO), one driver, and one receiver. The internal LDO allows the part to operate from an unregulated power supply of up to 28V. The AutoDirection feature reduces the number of optical isolators needed in isolated applications. Other features include enhanced ESD protection, fail-safe circuitry, slew-rate limiting, and fullspeed operation. The MAX13410E–MAX13415E internal LDO generates a 5V ±10% power supply that is used to power its internal circuitry. The MAX13412E–MAX13415E bring the 5V to an output VREG that allows the user to power additional external circuitry with up to 20mA to further reduce external components. The MAX13410E/MAX13411E do not have a 5V output and come in industry-compatible pinouts. This allows easy replacement in existing designs. The MAX13410E–MAX13415E feature a 1/8-unit load receiver input impedance, allowing up to 256 transceivers on the bus. All driver outputs are ESD protected using the Human Body Model. These devices also include fail-safe circuitry (MAX13410E/MAX13411E/ MAX13414E/MAX13415E only), guaranteeing a logichigh receiver output when the receiver inputs are open or shorted. The receiver outputs a logic-high when the transmitter on the terminated bus is disabled (high impedance). The MAX13412E/MAX13413E feature Maxim’s proprietary AutoDirection control. This architecture eliminates the need for the DE and RE control signals. In isolated applications, this reduces the cost and size of the system by reducing the number of optical isolators required. The MAX13410E/MAX13412E/MAX13414E feature reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission up to 500kbps. The MAX13411E/MAX13413E/MAX13415E are not slew-rate limited, allowing transmit speeds up to 16Mbps. The MAX13410E–MAX13415E are available in an 8-pin SO package with an exposed paddle to improve power dissipation, and operate over the extended -40°C to +85°C temperature range. Features ♦ Wide +6V to +28V Input Supply Range ♦ +5V Output Supplies Up to 20mA to External Circuitry ♦ Internal LDO ♦ Low 65µA (typ) Shutdown Supply Current ♦ Extended ESD Protection ±15kV Human Body Model (MAX13412E/ MAX13413E) ±14kV Human Body Model (MAX13410E/ MAX13411E) ♦ 1/8-Unit Load, Allowing Up to 256 Transceivers on the Bus ♦ -40°C to +85°C Operating Temperature Range ♦ Fail-Safe ♦ Slew-Rate Limited and Full-Speed Versions ♦ Up to 16Mbps Data Rate on Full-Speed Versions MAX13410E–MAX13415E Applications Isolated RS-485 Interfaces Utility Meters Industrial Equipment Telecomm Equipment Pin Configurations TOP VIEW RO RE DE 1 2 3 + 8 7 VCC B A GND MAX13410E MAX13411E *EP 6 5 DI 4 SO *EXPOSED PAD CONNECTED TO GROUND Pin Configurations continued at end of data sheet. Ordering Information/Selector Guide PART MAX13410EESA+ MAX13411EESA+ PIN-PACKAGE 8 SO-EP* 8 SO-EP* AutoDirection No No DATA RATE (max) 500kbps 16Mbps 5V LDO OUTPUT No No Note: All devices operate over the -40°C to +85°C operating temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Ordering Information/Selector Guide continued at end of data sheet. 1 ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND.) VCC .........................................................................-0.3V to +30V RE, DE/RE, DE, DI, RO, VREG ..................................-0.3V to +6V A, B............................................................................-8V to +13V Short-Circuit Duration (RO, A, B) to GND ................. Continuous Continuous Power Dissipation (TA = +70°C) 8-Pin SO-EP (derate 19.2mW/°C above +70°C) ........1539mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range ............................-65°C to +150°C Junction Temperature ......................................................+150°C θJA (Note 1)...................................................................52.0°C/W θJC (Note 1).....................................................................6.0°C/W Lead Temperature (soldering, 10s) ................................+300°C Note 1: Package thermal resistances were obtained using the method described in JEDEC specificactions JESD51-7 using a four layer board. For detailed information on package consitencies refer to www.maxim-ic/thermal-tutorial. 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 = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER Supply Voltage LDO Output Voltage LDO Output Current LDO Dropout Voltage Minimum Bypass Capacitor on VREG SYMBOL VCC VREG IREG VDO CS (Note 3) VCC = +7.5V, ILOAD = 20mA VCC = +28V, ILOAD = 0mA VCC > +7.5V VCC = +5V, IOUT = 20mA Guaranteed by design, MAX13412E–MAX13415E RE, DE = high/no load (MAX13410E/MAX13411E) Supply Current ICC RE, DE/RE = high, DI = low/no load (MAX13412E–MAX13415E) DE = low, RE = high (MAX13410E/MAX13411E) 45 +150 15 1 10 mA 10 µA °C °C 0.5 CONDITIONS MIN 6.0 4.5 4.5 5 5 TYP MAX 28.0 5.5 5.5 20 UNITS V V mA V µF Shutdown Current Thermal-Shutdown Threshold Thermal-Shutdown Threshold Hysteresis DRIVER ISHDN TTS TTSH RDIFF = 100Ω, Figure 1 Differential Driver Output Change in Magnitude of Differential Output Voltage Driver Common-Mode Output Voltage Change In Magnitude of CommonMode Voltage Input High Voltage Input Low Voltage Input Current Driver-Disable Threshold VOD RDIFF = 54Ω, Figure 1 No load ΔVOD VOC ΔVOC VIH VIL IIN VDT RDIFF = 100Ω or 54Ω, Figure 1 RDIFF = 100Ω or 54Ω, Figure 1 RDIFF = 100Ω or 54Ω, Figure 1 DI, DE, RE, DE/RE DI, DE, RE, DE/RE DI, DE, RE, DE/RE TA = +25°C (MAX13412E/MAX13413E) 2.0 1.5 5.5 5.5 5.5 0.2 V V V V 0.8 ±1 V µA V V 1 3 0.2 2.0 0.6 1.0 2 _______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control ELECTRICAL CHARACTERISTICS (continued) (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER Driver Short-Circuit Output Current Driver Short-Circuit-Foldback Output Current RECEIVER Input Current (A and B) IA, B RE, DE, DE/RE = GND, VCC = GND VIN = +12V VIN = -7V -100 -200 -100 15 VREG - 0.6 0.4 0.01 96 ±8 ±95 ±1 -50 mV 100 mV V V µA kΩ mA 125 µA SYMBOL IOSD IOSDF CONDITIONS 0V < VOUT < +12V -7V < VOUT < 0V (VCC - 1V) < VOUT < +12V -7V < VOUT < 0V -250 20 -20 MIN TYP MAX +250 UNITS mA mA MAX13410E–MAX13415E Receiver Differential Threshold Voltage Receiver Input Hysteresis Output High Voltage Output Low Voltage Three-State Output Current at Receiver Receiver-Input Resistance Receiver-Output Short-Circuit Current ESD PROTECTION ESD Protection (A, B) ESD Protection (A, B) ESD Protection (All Other Pins) VTH -7V < VCM < +12V (MAX13410E/MAX13411E) -7V < VLM < +12V (MAX13412E/MAX13413E) VA + VB = 0V IO = -1mA, VA - VB > VTH IO = +1mA, VA - VB < -VTH 0 < VO < VREG -7V < VCM < +12V 0V < VRO < VREG Human Body Model (MAX13412E/MAX13413E) Human Body Model (MAX13410E/MAX13411E) Human Body Model ΔVTH VOH VOL IOZR RIN IOSR ±15 ±14 ±2 kV kV kV SWITCHING CHARACTERISTICS–MAX13410E (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER DRIVER Driver Propagation Delay Driver Differential Output Rise or Fall Time Driver Differential Output Skew |tDPLH - tDPHL| Maximum Data Rate Driver Enable from Shutdown to Output High Driver Enable from Shutdown to Output Low tDPLH tDPHL tHL tLH tDSKEW fMAX S2 closed, Figure 4, tDZH(SHDN) RL = 500Ω, CL = 100pF tDZL(SHDN) S2 closed, Figure 4, RL = 500Ω, CL = 100pF RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a 500 11 6 150 150 250 250 1000 1000 900 900 140 ns ns ns kbps µs µs SYMBOL CONDITIONS MIN TYP MAX UNITS _______________________________________________________________________________________ 3 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E SWITCHING CHARACTERISTICS–MAX13410E (continued) (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER Driver Enable to Output High Driver Enable to Output Low Driver Disable from Output High Driver Disable from Output Low Time to Shutdown RECEIVER Receiver Propagation Delay Receiver Output Skew Maximum Data Rate Receiver Enable to Output High Receiver Enable to Output Low Receiver Disable Time from High Receiver Disable Time from Low Receiver Enable from Shutdown to Output High Receiver Enable from Shutdown to Output Low tRPLH tRPHL tRSKEW fMAX tRZH tRZL tRZH tRLZ S2 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S2 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF CL = 15pF (at RO), Figures 5 and 6 CL = 15pF (at RO), Figures 5 and 6 500 50 50 50 50 14 3.5 200 200 30 ns ns kbps ns ns ns ns µs µs SYMBOL tDZH tDZL tDHZ tDLZ tSHDN CONDITIONS S2 closed, Figure 4, RL = 500Ω, CL = 100pF S1 closed, Figure 4, RL = 500Ω, CL = 100pF S2 closed, Figure 4, RL = 500Ω, CL = 100pF S1 closed, Figure 4, RL = 500Ω, CL = 100pF 50 340 MIN TYP MAX 2500 2500 100 100 700 UNITS ns ns ns ns ns tRZH(SHDN) S2 closed, Figure 7, CL = 15pF tRZL(SHDN) S1 closed, Figure 7, CL = 15pF SWITCHING CHARACTERISTICS–MAX13411E (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER DRIVER Driver Propagation Delay Driver Differential Output Rise or Fall Time Driver Differential Output Skew |tDPLH - tDPHL| Maximum Data Rate Driver Enable from Shutdown to Output High Driver Enable from Shutdown to Output Low Driver Enable to Output High tDPLH tDPHL tHL tLH tDSKEW fMAX S2 closed, Figure 4, tDZH(SHDN) RL = 500Ω, CL = 100pF tDZL(SHDN) tDZH S2 closed, Figure 4, RL = 500Ω, CL = 100pF S2 closed, Figure 4, RL = 500Ω, CL = 100pF RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a 16 11 6 70 50 50 15 15 8 ns ns ns Mbps µs µs ns SYMBOL CONDITIONS MIN TYP MAX UNITS 4 _______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control SWITCHING CHARACTERISTICS–MAX13411E (continued) (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER Driver Enable to Output Low Driver Disable from Output High Driver Disable from Output Low RECEIVER Receiver Propagation Delay Receiver Output Skew Maximum Data Rate Receiver Enable to Output High Receiver Enable to Output Low Receiver Disable Time from High Receiver Disable Time from Low Receiver Enable from Shutdown to Output High Receiver Enable from Shutdown to Output Low tRPLH tRPHL tRSKEW fMAX tRZH tRZL tRZH tRLZ S2 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S2 closed, Figure 7 , CL = 15pF S1 closed, Figure 7, CL = 15pF CL = 15pF (at RO), Figures 5 and 6 CL = 15pF (at RO), Figures 5 and 6 16 50 50 50 50 14 3.5 75 75 8 ns ns Mbps ns ns ns ns µs µs SYMBOL tDZL tDHZ tDLZ CONDITIONS S1 closed, Figure 4, RL = 500Ω, CL = 100pF S2 closed, Figure 4, RL = 500Ω, CL = 100pF S1 closed, Figure 4, RL = 500Ω, CL = 100pF MIN TYP MAX 70 50 50 UNITS ns ns ns MAX13410E–MAX13415E tRZH(SHDN) S2 closed, Figure 7, CL = 15pF tRZL(SHDN) S1 closed, Figure 7, CL = 15pF SWITCHING CHARACTERISTICS–MAX13412E (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER DRIVER Driver Propagation Delay Driver Differential Output Rise or Fall Time Maximum Data Rate Driver Disable Delay RECEIVER Receiver Propagation Delay Receiver Output Skew Maximum Data Rate Receiver Enable to Output High Receiver Enable to Output Low tRPLH tRPHL tRSKEW fMAX tRZH tRZL S2 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF CL = 15pF, Figures 5 and 6 CL = 15pF, Figures 5 and 6 500 50 50 200 200 30 ns ns kbps ns ns tDPLH tDPHL tHL tLH fMAX tDDD RL = 110Ω, CL = 50pF, Figure 3b RL = 110Ω, CL = 50pF, Figures 2b and 3b RL = 110Ω, CL = 50pF, Figures 2b and 3b 200 200 250 250 500 2500 1000 1000 900 900 ns ns kbps ns SYMBOL CONDITIONS MIN TYP MAX UNITS _______________________________________________________________________________________ 5 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E SWITCHING CHARACTERISTICS–MAX13412E (continued) (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER Receiver Disable Time from Low Receiver Disable Time from High Receiver Enable Delay SYMBOL tRLZ tRZH tRED CONDITIONS S1 closed, Figure 7, CL = 15pF S2 closed, Figure 7, CL = 15pF RL = 110Ω, CL = 50pF, Figure 3 MIN TYP MAX 50 50 2500 UNITS ns ns ns SWITCHING CHARACTERISTICS–MAX13413E (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER DRIVER Driver Propagation Delay Driver Differential Output Rise or Fall Time Maximum Data Rate Driver Disable Delay RECEIVER Receiver Propagation Delay Receiver Output Skew Maximum Data Rate Receiver Enable to Output High Receiver Enable to Output Low Receiver Disable Time from Low Receiver Disable Time from High Receiver Enable Delay tRPLH tRPHL tRSKEW fMAX tRZH tRZL tRLZ tRZH tRED S2 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S2 closed, Figure 7, CL = 15pF RL = 110Ω, Figure 3, CL = 50pF CL = 15pF, Figures 5 and 6 CL = 15pF, Figures 5 and 6 16 50 50 50 50 70 80 80 13 ns ns Mbps ns ns ns ns ns tDPLH tDPHL tHL tLH fMAX tDDD RL = 110Ω, CL = 50pF, Figure 3b RL = 110Ω, CL = 50pF, Figures 2b and 3b RL = 110Ω, CL = 50pF, Figures 2b and 3b 16 70 50 50 15 15 ns ns Mbps ns SYMBOL CONDITIONS MIN TYP MAX UNITS SWITCHING CHARACTERISTICS–MAX13414E (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER DRIVER Driver Propagation Delay Driver Differential Output Rise or Fall Time Driver Differential Output Skew |tDPLH - tDPHL| tDPLH tDPHL tHL tLH tDSKEW RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a 200 200 250 250 1000 1000 900 900 140 ns ns ns SYMBOL CONDITIONS MIN TYP MAX UNITS 6 _______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E SWITCHING CHARACTERISTICS–MAX13414E (continued) (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER Maximum Data Rate Driver Enable to Output High Driver Enable to Output Low Driver Disable from Output High Driver Disable from Output Low RECEIVER Receiver Propagation Delay Receiver Output Skew Maximum Data Rate Receiver Enable to Output High Receiver Enable to Output Low Receiver Disable Time from Low Receiver Disable Time from High tRPLH tRPHL tRSKEW fMAX tRZH tRZL tRLZ tRZH S2 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S2 closed, Figure 7, CL = 15pF CL = 15pF (at RO), Figures 5 and 6 CL = 15pF (at RO), Figures 5 and 6 500 50 50 50 50 200 200 30 ns ns kbps ns ns ns ns SYMBOL fMAX tDZH tDZL tDHZ tDLZ S2 closed, Figure 4, RL = 500Ω CL = 100pF S1 closed, Figure 4, RL = 500Ω CL = 100pF S2 closed, Figure 4, RL = 500Ω, CL = 100pF S1 closed, Figure 4, RL = 500Ω, CL = 100pF CONDITIONS MIN 500 2500 2500 100 100 TYP MAX UNITS kbps ns ns ns ns SWITCHING CHARACTERISTICS–MAX13415E (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER DRIVER Driver Propagation Delay Driver Differential Output Rise or Fall Time Driver Differential Output Skew |tDPLH - tDPHL| Maximum Data Rate Driver Enable to Output High Driver Enable to Output Low Driver Disable from Output High tDPLH tDPHL tHL tLH tDSKEW fMAX tDZH tDZL tDHZ S2 closed, Figure 4, RL = 500Ω, CL = 15pF S1 closed, Figure 4, RL = 500Ω, CL = 15pF S2 closed, Figure 4, RL = 500Ω, CL = 15pF RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a RDIFF = 54Ω, CL = 50pF, Figures 2a and 3a 16 70 70 50 50 50 15 15 8 ns ns ns Mbps ns ns ns SYMBOL CONDITIONS MIN TYP MAX UNITS _______________________________________________________________________________________ 7 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E SWITCHING CHARACTERISTICS–MAX13415E (continued) (VCC = +6.0V to +28V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +7.5V, CS = 1µF, and TA = +25°C.) (Note 2) PARAMETER Driver Disable from Output Low RECEIVER Receiver Propagation Delay Receiver Output Skew Maximum Data Rate Receiver Enable to Output High Receiver Enable to Output Low Receiver Disable Time from Low Receiver Disable Time from High tRPLH tRPHL tRSKEW fMAX tRZH tRZL tRLZ tRZH S2 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S1 closed, Figure 7, CL = 15pF S2 closed, Figure 7, CL = 15pF CL = 15pF (at RO), Figures 5 and 6 CL = 15pF (at RO), Figures 5 and 6 16 50 50 50 50 75 75 8 ns ns Mbps ns ns ns ns SYMBOL tDLZ CONDITIONS S1 closed, Figure 4, RL = 500Ω, CL = 15pF MIN TYP MAX 50 UNITS ns Note 2: CS is the compensation capacitor on VREG for the MAX13412E–MAX13415E versions. CS must have an ESR value of 20mΩ or less. Note 3: Parameters are guaranteed for +6.0V ≤ VCC ≤ +28V. Typical Operating Characteristics (VCC = +7.5V, TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. TEMPERATURE NO LOAD MAX13410E-15E toc01 OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE MAX13410E-15E toc02 OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE MAX13410E-15E toc03 8.0 35 30 OUTPUT CURRENT (mA) 25 20 15 10 5 0 60 50 OUTPUT CURRENT (mA) 40 30 20 10 0 SUPPLY CURRENT (mA) 6.0 4.0 DE = HIGH 2.0 DE = LOW 0 -40 -15 10 35 60 85 TEMPERATURE (°C) 0 1 2 3 4 5 0 1 2 3 4 5 OUTPUT HIGH VOLTAGE (V) OUTPUT LOW VOLTAGE (V) 8 _______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control Typical Operating Characteristics (continued) (VCC = +7.5V, TA = +25°C, unless otherwise noted.) MAX13410E–MAX13415E RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE MAX13410E-15E toc04 RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE MAX13410E-15E toc05 DIFFERENTIAL OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE MAX13410E-15E toc06 5.4 5.2 OUTPUT HIGH VOLTAGE (V) 5.0 4.8 4.6 4.4 4.2 IO = +1mA 0.5 IO = -1mA 80 OUTPUT LOW VOLTAGE (V) 0.4 0.3 OUTPUT CURRENT (mA) 60 40 0.2 0.1 20 4.0 -40 0 -15 10 35 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) TEMPERATURE (°C) 0 0 1 2 3 4 5 OUTPUT VOLTAGE (V) DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE RDIFF = 54Ω 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -40 -15 10 35 60 85 TEMPERATURE (°C) MAX13410E-15E toc07 OUTPUT CURRENT vs. TRANSMITTER OUTPUT HIGH VOLTAGE MAX13410E-15E toc08 OUTPUT CURRENT vs. TRANSMITTER OUTPUT LOW VOLTAGE MAX13410E-15E toc09 4.0 DIFFERENTIAL OUTPUT VOLTAGE (V) 120 100 OUTPUT CURRENT (mA) 80 60 40 20 0 -7 -6 -5 -4 -3 -2 -1 01 2 3 4 5 OUTPUT HIGH VOLTAGE (V) 120 100 OUTPUT CURRENT (mA) 80 60 40 20 0 0 2 4 6 8 10 12 OUTPUT LOW VOLTAGE (V) SHUTDOWN CURRENT vs. TEMPERATURE MAX13410E-15E toc10 DRIVER PROPAGATION vs. TEMPERATURE (MAX13412E) RL = 110Ω MAX13410E-15E toc11 DRIVER PROPAGATION vs. TEMPERATURE (MAX13413E) RL = 110Ω 35 30 tRPHL 25 20 15 10 tRPLH 5 0 MAX13410E-15E toc12 100 90 SHUTDOWN CURRENT (μA) 80 70 60 50 40 30 20 10 0 -40 -15 10 35 60 700 DRIVER PROPAGATION DELAY (ns) 600 500 400 300 200 100 40 DRIVER PROPAGATION DELAY (ns) tRPLH tRPHL 85 0 -40 -15 10 35 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) _______________________________________________________________________________________ 9 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Typical Operating Characteristics (continued) (VCC = +7.5V, TA = +25°C, unless otherwise noted.) RECEIVER PROPAGATION vs.TEMPERATURE (MAX13410E/MAX13412E) MAX13410E-15E toc13 RECEIVER PROPAGATION vs.TEMPERATURE (MAX13411E/MAX13413E) MAX13410E-15E toc14 DRIVER PROPAGATION (250kbps) (MAX13412E) MAX13410E-15E toc15 60 RECEIVER PROPAGATION DELAY (ns) tRPHL 45 60 RECEIVER PROPAGATION DELAY (ns) 45 tRPHL 30 DI 2V/div 30 tRPLH 15 15 tRPLH 0 1μs/div A-B 5V/div 0 -40 -15 10 35 60 85 TEMPERATURE (°C) -40 -15 10 35 60 85 TEMPERATURE (°C) DRIVER PROPAGATION (16kbps) (MAX13413E) MAX13410E-15E toc16 RECEIVER PROPAGATION (16kbps) (MAX13413E) MAX13410E-15E toc17 DRIVING A LARGE CAPACITIVE LOAD 16nF (19.2kbps) (MAX13412E) MAX13410E-15E toc18 DI 2V/div A 2V/div DI 2V/div B 2V/div A-B 5V/div RO 2V/div A-B 2V/div 20ns/div 20ns/div 10μs/div DRIVING A LARGE CAPACITIVE LOAD 16nF (1Mbps) (MAX13413E) MAX13410E-15E toc19 DRIVING A LARGE CAPACITIVE LOAD 16nF (50kbps) (MAX13413E) MAX13410E-15E toc20 DI 2V/div DI 2V/div A-B 5V/div A-B 2V/div 400ns/div 1μs/div 10 ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control Test Circuits and Waveforms A RDIFF / 2 VOD CL RDIFF / 2 VOC B MAX13410E–MAX13415E Figure 1. Driver DC Test Load 5V DE RL DI A VID B RDIFF CL DI A VID B VREG GND RL CL Figure 2a. Driver-Timing Test Circuit Figure 2b. Driver-Timing Test Circuit 5V DI 0 1.5V f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns 1.5V 1/2 VO tDPLH B A 1/2 VO VO VO VDIFF 0 -VO 10% tLH tDSKEW = |tDPLH - tDPHL| 90% VDIFF = VA - VB tDPHL 90% 10% tHL Figure 3a. Driver Propagation Delays ______________________________________________________________________________________ 11 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Test Circuits and Waveforms (continued) 5V DI 0 1.5V RE = VCC f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns 1.5V 1/2 VO tDPLH B VO A 1/2 VO RO O VO VDIFF 0 -VO tLH 10% (RO PULLED LOW) VDIFF = VA - VB 90% tDDD, tRED tDPHL 90% 10% tHL Figure 3b. Driver Propagation Delays VCC DE 0 tDZL(SHDN) A, B OUTPUT UNDER TEST CL 500Ω S1 S2 A, B 2.3V 0 tDZH(SHDN) tDHZ 5V VOL 2.3V OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH VOH + 0.5V VOL + 0.5V tDLZ 1.5V 1.5V VOH Figure 4. Driver Enable and Disable Times B ATE VID A R RECEIVER OUTPUT Figure 5. Receiver-Propagation-Delay Test Circuit 12 ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control Test Circuits and Waveforms (continued) f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns MAX13410E–MAX13415E A B 1V -1V tRPHL VOH RO VOL 1.5V tRSKEW = | tRPHL - tRPLH | tRPLH 1.5V Figure 6. Receiver Propagation Delays VREG RE 0 tRZL(SHDN), tRZL VREG 1kΩ RO CL 15pF S1 S2 VREG RO 0 DI = 0V tRZH(SHDN), tRZH tRHZ 2.3V 5V RO 0 2.3V VOH + 0.5V OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH VOH + 0.5V tRHZ 1.5V 1.5V Figure 7. Receiver Enable and Disable Times ______________________________________________________________________________________ 13 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Pin Description PIN MAX13410E/ MAX13411E 1 MAX13412E/ MAX13413E — MAX13414E/ MAX13415E 1 NAME FUNCTION Receiver Output. When receiver is enabled and VA - VB ≥ -50mV, RO is high. If VA - VB ≤ -200mV, RO is low. Note: RO is referenced to the LDO output (VREG). Receiver Output Enable. Drive RE low to enable RO. Drive RE high to disable the RO output and put the RO output in a high-impedance state. Driver Output Enable. Drive DE low to put the driver output in three-state. Drive DE high to enable the driver. Driver Input. Drive DI low to force the noninverting output low and the inverting output high. Drive DI high to force the noninverting output high and inverting output low. DI is an input to the internal state machine that automatically enables and disables the driver (for the MAX13412E/MAX13413E). See the function tables and General Description for more information. Ground Noninverting Receiver Input and Noninverting Driver Output Inverting Receiver Input and Inverting Driver Output Positive Supply. Bypass VCC with a 0.1µF ceramic capacitor to GND. Receiver Output. When receiver is enabled and VA - VB ≥ -100mV, RO is high. If VA - VB ≤ -100mV, RO is low. Note: RO is referenced to the LDO output (VREG). Receiver Output Enable. Drive RE low to force the RO output to be enabled. Drive RE high to let the AutoDirection circuit control RO. LDO Output. VREG is fixed at +5V. Bypass VREG with a low ESR (20mΩ or less) and a 1µF (min) ceramic capacitor. Receiver and Driver Output Enable. Drive DE/RE low to enable RO and disable the driver. Drive DE/RE high to disable RO and enable the driver. Exposed Pad. EP is internally connected to GND. For enhanced thermal dissipation, connect EP to a copper area as large as possible. Do not use EP as a sole ground connection. RO 2 — — RE 3 — — DE 4 4 4 DI 5 6 7 8 — 5 6 7 8 1 5 6 7 8 — GND A B VCC RO RE VREG DE/RE — — 2 3 — 3 — — 2 EP EP EP EP 14 ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control Function Tables for the MAX13410E/MAX13411E TRANSMITTING INPUT RE X X 0 1 DE 1 1 0 0 DI 1 0 X X B 0 1 High impedance OUTPUT A 1 0 High impedance RE 0 0 0 1 1 DE X X X 1 0 INPUT A-B > -50mV < -200mV Open/Short X X RECEIVING OUTPUT RO 1 0 1 High impedance High impedance (shutdown) MAX13410E–MAX13415E High impedance (shutdown) X = Don’t care, shutdown mode, driver, and receiver outputs are in high impedance. Function Tables for the MAX13412E/MAX13413E TRANSMITTING INPUTS DI 0 1 1 1 A - B > VDT X False False True ACTION Turn driver ON If driver was OFF, keep it OFF If driver was ON, keep it ON Turn driver OFF A 0 High impedance 1 High impedance OUTPUTS B 1 High impedance 0 High impedance RECEIVING INPUTS RE 0 0 1 1 1 A-B > -100mV < -100mV X > -100mV < -100mV DRIVER STATE X X ON OFF OFF RECEIVER STATE ON ON OFF ON ON OUTPUT RO 1 0 High impedance 1 0 X = Don’t care, shutdown mode, driver, and receiver outputs are in high impedance. Function Tables for the MAX13414E/MAX13415E TRANSMITTING INPUT DE/RE 0 1 1 DI X 1 0 B High impedance 0 1 OUTPUT A High impedance 1 0 DE/RE 0 0 0 1 INPUT A-B > -50mV < -200mV Open/Short X RECEIVING OUTPUT RO 1 0 1 High impedance X = Don’t care, shutdown mode, driver, and receiver outputs are in high impedance. ______________________________________________________________________________________ 15 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Detailed Description The MAX13410E–MAX13415E are half-duplex RS-485/ RS-422-compatible transceivers optimized for isolated applications. These devices feature an internal LDO regulator, one driver, and one receiver. The internal LDO allows the part to operate from an unregulated +6V to +28V power supply. The AutoDirection feature reduces the number of optical isolators needed in isolated applications. Other features include ±15kV ESD protection (MAX13412E/MAX13413E only), ±14kV (MAX13410E/ MAX13411E only) fail-safe circuitry, slew-rate limiting, and full-speed operation. The MAX13410E–MAX13415E internal LDO generates a 5V ±10% power supply that is used to power its internal circuitry. The MAX13412E–MAX13415E bring the 5V to an output VREG that allows the user to power additional external circuitry with up to 20mA to further reduce external components. The MAX13410E/MAX13411E do not have a 5V output and come in industry-compatible pinouts. This allows easy replacement in existing designs. The MAX13412E/MAX13413E feature Maxim’s proprietary AutoDirection control. This architecture eliminates the need for the DE and RE control signals. In isolated applications, this reduces the cost and size of the system by reducing the number of optical isolators required. The MAX13410E/MAX13412E/MAX13414E feature reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission up to 500kbps. The MAX13411E/MAX13413E/MAX13415E are not slew-rate limited, allowing transmit speeds up to 16Mbps. The MAX13410E–MAX13415E feature a 1/8-unit load receiver input impedance, allowing up to 256 transceivers on the bus. All driver outputs are protected to ±15kV ESD using the Human Body Model. These devices also include fail-safe circuitry, MAX13410E/ MAX13411E/MAX13414E/MAX13415E, guaranteeing a logic-high receiver output when the receiver inputs are open or shorted. The receiver outputs a logic-high when the transmitter on the terminated bus is disabled (high impedance). When using these devices with high input voltages and heavily loaded networks, special care must be taken that the power dissipation rating of the package and the maximum die temperature of the device is not exceeded. Die temperature of the part can be calculated using the equation: TDIE = [(θJC + θCA) x PDISS] + TAMBIENT, where TDIE = Temperature of the Die θJC = 6.0°C/W = Junction-to-Case Thermal Resistance θCA = Case-to-Ambient Thermal Resistance θJA = θJC + θCA = 52.0°C/W = Junction-to-Ambient Thermal Resistance PDISS = (ICC - VCC) + [(VCC - VREG) x IREG)] + [(VCC VOD) x IDRIVER] = Power Dissipation of the Part TAMBIENT = Ambient Temperature VCC = Voltage on the VCC Input ICC = Current in to VCC VREG = Voltage on the VREG Output IREG = Current Drawn from the VREG Output VOD = Voltage at the Driver Output (|VA - VB|) IDRIVER = Current Driven Out of the Driver. Typically, this is the current through the termination resistor. The absolute maximum rating of the die temperature of the MAX13410E–MAX13415E is +150°C. To protect the part from overheating, there is an internal thermal shutdown that shuts down the part when the die temperature reaches +150°C. To prevent damage to the part, and to prevent the part from entering thermal shutdown, keep the die temperature below +150°C, plus some margin. The circuit designer can minimize the die temperature by controlling the following parameters: • VCC • • IREG θCA Internal Low-Dropout Regulator The MAX13410E–MAX13415E include an internal lowdropout regulator that allows it to operate from input voltages of up to +28V. The internal LDO has a set output voltage of 5V ±10% that is used to power the internal circuitry of the device. The MAX13412E–MAX13415E offer the LDO output at the VREG output. This allows additional external circuitry to be powered without the need for additional external regulators. The VREG output can source up to 20mA. 16 Measuring the VCC Current Measured current at the VCC pin is a function of the quiescent current of the part, the amount of current that the drivers must supply to the load, and in the case of the MAX13412E–MAX13415E, the load on the VREG output. In most cases, the load that the drivers must supply will be the termination resistor(s). Ideally, the termination resistance should match the characteristic impedance of the cable and is usually not a parameter the circuit designer can easily change. In some lowspeed, short-cable applications, proper termination ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Functional Diagrams Functional Diagram for the MAX13410E/MAX13411E/MAX13414E/MAX13415E MAX13410E MAX13411E + RO 1 RE 2 DE 3 D R LDO 8 7 6 5 VCC B A GND RO 1 DE/RE 2 VREG 3 D + R LDO 8 7 6 5 VCC B A GND MAX13414E MAX13415E DI 4 DI 4 Functional Diagram for the MAX13412E/MAX13413E VREG MAX13412E MAX13413E 1 RO RE RE VREG + R 2 LDO VCC 8 3 VREG COM - VDT B7 A6 + RI DI STATE MACHINE DE VREG 4 DI D 5 GND may not be necessary. In these cases, the drive current can be reduced to minimize the die temperature. Minimizing the load on the V REG output lowers the power dissipation of the part and ultimately reduces the maximum die temperature. θCA θCA is the thermal resistance from case to ambient and is independent of the MAX13410E–MAX13415E. θCA is primarily a characteristic of the circuit-board design. The largest contributing factor of θCA will be the size and weight of the copper connected to the exposed paddle of the MAX13410E–MAX13415E. Lower the thermal resistance by using as large a pad as possible. Additionally, vias can be used to connect the pad to other ground planes in the circuit board. Note that θJC is the thermal resistance of the part from junction-to-case temperature and is fixed at 6.0°C/W. It is solely based on the die and package characteristics of 17 ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E the MAX13410E–MAX13415E. The circuit-board designer has no control over this parameter. Fail Safe The MAX13410E/MAX13411E/MAX13414E/MAX13415E guarantee a logic-high receiver output when the receiver inputs are shorted or open, or when they are connected to a terminated transmission line with all drivers disabled. This is done by setting the receiver input threshold between -50mV and -200mV. If the differential receiver input voltage (A - B) is greater than or equal to -50mV, RO is logic-high. If (A - B) is less than or equal to -200mV, RO is logic-low. In the case of a terminated bus with all transmitters disabled, the receiver’s differential input voltage is pulled to 0 by the termination. With the receiver thresholds of the MAX13410E/ MAX13411E/MAX13414E/MAX13415E, the result is a logic-high with a 50mV minimum noise margin. Unlike previous fail-safe devices, the -50mV to -200mV threshold complies with the ±200mV EIA/TIA-485 standard. high, the drivers actively drive the output until (A - B) > VDT. Once (A - B) is greater than VDT, the drivers are disabled, letting the pullup/pulldown resistors hold the A and B lines in the correct state. This allows other transmitters on the bus to pull the bus low. Pullup and Pulldown Resistors The pullup and pulldown resistors on the A and B lines are required for proper operation of the MAX13412E and MAX13413E, although their exact value is not critical. They function to hold the bus in the high state (A - B > 200mV) when all the transmitters are in a high-impedance state due to either a shutdown condition or AutoDirection. Determining the best value to use for these resistors depends on many factors, such as termination resistor values, noise, number of transceivers on the bus, etc. Size these resistors so that, under all conditions, (A - B) > 200mV for ALL receivers on the bus. Idle State When not transmitting data, the MAX13412E/ MAX13413E require the DI input to be driven high to remain in the idle state. A conventional RS-485 transceiver has DE and RE inputs that are used to enable and disable the driver and receiver. However, the MAX13412E/MAX13413E do not have a DE input, and instead use an internal state machine to enable and disable the drivers. DI must be driven high to go to the idle state. AutoDirection Circuitry The AutoDirection circuitry in the MAX13412E/ MAX13413E is a technique to minimize the number of signals needed to drive the part. This is especially useful in very low cost, isolated systems. In a typical isolated system, an optocoupler is used for each control signal to cross the isolation barrier. These optocouplers add cost, size and consume power. Without the AutoDirection circuitry, three to four optocouplers may be required for each transceiver. With the AutoDirection circuitry, the number of optocouplers can be reduced to two. Typical RS-485 transceivers have four signals on the control side of the part. These are RO (receiver output), RE (receiver enable), DE (driver enable), and DI (driver input). In some cases, DE and RE may be connected together to reduce the number of control signals to three. In half-duplex systems, the RE and DE signals determine if the part is transmitting or receiving. When the part is receiving, the transmitter is in a high-impedance state. In a fully compliant RS-485 system, all three or four signals are required. However, with careful design and Maxim’s AutoDirection feature, the number of control signals can be reduced to just RO and DI in an RS-485 compatible system. This feature assumes the DI input idles in the high state while the receiver portion of the MAX13412E/MAX13413E is active. It also requires an external pullup resistor on A and pulldown resistor on B (see the typical application circuit, Figure 10). The following is a description of how AutoDirection works. When DI is low, the MAX13412E/MAX13413E always drive the bus low. When DI transitions from a low to a Enhanced 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 of the MAX13410E– MAX13415E have extra protection against static electricity. Maxim’s engineers have developed state-of-the-art structures to protect these pins against ESD of ±15kV (MAX13412E/MAX13413E) and ±14kV (MAX13410E/ MAX13411E) without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD event, the MAX13410E– MAX13415E keep working without latchup or damage. ESD protection can be tested in various ways. The transmitter outputs and receiver inputs of the MAX13410E– MAX13415E are characterized for protection to the following limits: ±15kV using the Human Body Model (MAX13412E/ MAX13413E) ±14kV using the Human Body Model (MAX13410E/ MAX13411E) 18 ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E RC 1MΩ CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE RD 1500Ω DISCHARGE RESISTANCE DEVICE UNDER TEST IP 100% 90% AMPS 36.8% 10% 0 0 tRL TIME Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) Cs 100pF STORAGE CAPACITOR tDL CURRENT WAVEFORM Figure 8a. Human Body ESD Test Model Figure 8b. Human Body Current Waveform ESD Test Conditions ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, test methodology, and test results. Human Body Model Figure 8a shows the Human Body Model, and Figure 8b shows the current waveform it generates when discharged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a 1.5kΩ resistor. Typical Application Circuit for the MAX13412E and MAX13413E This application circuit shows the MAX13412E and MAX13413E being used in an isolated application where the AutoDirection feature is implemented to reduce the number of optical isolators to two (see Figure 10). The MAX13412E/MAX13413E provide a VREG output that can be used to power external circuitry up to 20mA. Typical Application Circuit for the MAX13414E and MAX13415E This application circuit shows the MAX13414E/ MAX13415E being used in an isolated application using an unregulated power supply with three optical isolators (see Figure 11). The MAX13414E/MAX13415E provide a VREG output that can be used to power external circuitry up to 20mA. Applications Information Typical Applications The MAX13410E–MAX13415E transceivers are designed for half-duplex, bidirectional data communications on multipoint bus transmission lines. To minimize reflections, terminate the line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. The slew-rate-limited MAX13410E/ MAX13412E/MAX13414E are more tolerant of imperfect termination. 256 Transceivers on the Bus The RS-485 standard specifies the load each receiver places on the bus in terms of unit loads. An RS-485compliant transmitter can drive 32 one-unit load receivers when used with a 120Ω cable that is terminated on both ends over a -7V to +12V common-mode range. The MAX13410E–MAX13415E are specified as 1/8 unit loads. This means a compliant transmitter can drive up to 256 devices of the MAX13410E–MAX13415E. Reducing the common mode, and/or changing the characteristic impedance of the cable, changes the maximum number of receivers that can be used. Refer to the TIA/EIA-485 specification for further details. Typical Application Circuit for the MAX13410E and MAX13411E This application circuit shows the MAX13410E/ MAX13411E being used in an isolated application (see Figure 9). The MAX13410E/MAX13411E use the industrystandard pin out but do not have a VREG output for biasing external circuitry. The positive temperature coefficient (PTC) and transient voltage suppressor (TVS) clamp circuit on the RS-485 outputs are intended to provide overvoltage fault protection and are optional based on the requirements of the design. Proper Termination and Cabling/ Wiring Configurations When the data rates for RS-485 are high relative to the cable length it is driving, the system is subject to proper ______________________________________________________________________________________ 19 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Rt ISO_VCC VSYS + RO LDO 8 VCC ISO_VCC 0.1μF B UNREGULATED ISOLATED POWER SUPPLY MCU AND RELATED CIRCUITRY ISO_VCC N 1 R RE 2 7 DE ISO_VCC DI 3 6 A 4 D MAX13410E MAX13411E 5 GND Rt Figure 9. Typical Application Circuit for the MAX13410E/MAX13411E transmission line design. In most cases, a single, controlled-impedance cable or trace should be used and should be properly terminated on both ends with the characteristic impedance of the cable/trace. RS-485 transceivers should be connected to the cable/ traces with minimum-length wires to prevent stubs. Star configurations and improperly terminated cables can cause data loss. Refer to the Application Notes section of the Maxim website or to TIA/EIA publication TSB-89-A for further information. While proper termination is always desirable, in some cases, such as when data rates are very low, it may be desirable and advantageous to not properly terminate the cables. In such cases, it is up to the designer to ensure that the improper termination and resultant reflections (etc.) will not corrupt the data. RE high. In shutdown, the devices draw 65µA (typ) of supply current. The devices are guaranteed not to enter shutdown if DE is low (while RE is high) for less than 50ns. If the inputs are in this state for at least 700ns, the devices are guaranteed to enter shutdown. Enable times tZH and tZL (see the switching characteristics table) assume the devices were not in a low-power shutdown state. Enable times tZH(SHDN) and tZL(SHDN) assume the devices were in shutdown state. It takes drivers and receivers longer to become enabled from lowpower shutdown mode (tZH(SHDN), tZL(SHDN)) than from driver/receiver disable mode (tZH, tZL). Line Length The Telecommunications Industry Association (TIA) published the document TSB-89-A: Application Guidelines for TIA/EIA-485-A, which is a good reference for determining maximum data rate vs. line length. Reduced EMI and Reflections The MAX13410E/MAX13412E/MAX13414E feature reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps. Isolated RS-485 Interface An isolated RS-485 interface electrically isolates different nodes on the bus to protect the bus from problems due to high common-mode voltages that exceed the RS-485 common-mode voltage range, conductive noise, and Low-Power Shutdown Mode Low-power shutdown mode is initiated in the MAX13410E/MAX13411E by driving DE low and driving 20 ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Rt ISO_VCC VSYS UNREGULATED ISOLATED POWER SUPPLY + RO MCU AND RELATED CIRCUITRY ISO_VCC ISO_VCC RE ISO_VCC VREG VSYS CS 1μF DI 3 2 DETECT CIRCUIT 7 B LDO VCC 0.1μF 1 R 8 6 A 4 D MAX13412E MAX13413E 5 GND ISO_VCC Rt Figure 10. Typical Application Circuit for the MAX13412E/MAX13413E ground loops. The typical application circuits show an isolated RS-485 interface using the MAX13410E– MAX13415E. The transceiver is powered separately from the controlling circuitry. The AutoDirection feature of the MAX13412E/MAX13413E (see the AutoDirection Circuitry section) requires only two optocouplers to electrically isolate the transceiver. An isolated RS-485 interface electrically isolates different nodes on the bus to protect the bus from problems due to high common-mode voltages that exceed the RS-485 common-mode voltage range. An isolated RS485 interface has two additional design challenges not normally associated with RS-485 design. These are 1) isolating the control signals and 2) getting isolated power to the transceiver. Optical isolators are the most common way of getting the control signals across the isolation barrier. Isolated power is typically done using a transformer in either a push-pull or flyback configuration. The MAX845 is an example of an inexpensive, unregulated push-pull converter (see Figure 12). While in theory, the output of an unregulated push-pull converter is predictable, the output voltage can vary significantly due to the non-ideal characteristics of the transformer, load variations, and temperature drift of the diodes, etc. Variances of ±20% or more would not be uncommon. This would require the addition of a linear regulator to get standard RS-485 transceivers to work. Since the MAX13410E– MAX13415E have the linear regulator built in, this external regulator and its associated cost and size penalties are not necessary. A nominal +7.5V output with a ±20% tolerance would provide a +6V to +9V supply voltage. This is well within the operating range of the MAX13410E–MAX13415E. If the output tolerance is even greater than ±20%, adjust the design of the power supply for a higher output voltage to ensure the minimum input voltage requirements are met. Flyback converters are typically regulated. A TL431 type error amplifier and an optical isolator usually close the loop. The MAX5021 is an example of a small, inexpensive, flyback controller (see Figure 13). While the primary output of the flyback converter is tightly regulated, secondary outputs will not be. As with the unregulated push-pull converter, the MAX13410E–MAX13415E are ideally suited for use with these secondary outputs. ______________________________________________________________________________________ 21 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Rt ISO_VCC VSYS ISO_VCC + VSYS MCU AND RELATED CIRCUITRY ISO_VCC RO VCC 0.1μF B UNREGULATED ISOLATED POWER SUPPLY 1 R LDO 8 DE/RE ISO_VCC VREG VSYS CS 1μF DI 2 7 3 6 A 4 D MAX13414E MAX13415E 5 GND Rt Figure 11. Typical Application Circuit for the MAX13414E/MAX13415E ON / OFF 4 SD 6 VCC D1 VIN 5V C1 VSUPPLY 1 CR1 OUTPUT 5V AT 150mA VOUT C2 MAX845 3 FREQUENCY SELECT FS GND1 2 D2 GND2 7 CR2 8 T1 C3 VCC VIN MAX5021/ MAX5022 OPTO NDRV GND CS Figure 12. Using the MAX845 to Obtain an Isolated Power Supply Figure 13. The MAX5021 and MAX5022 provide an isolated power supply with tighter regulation due to feedback using an opto-isolator coupler. 22 ______________________________________________________________________________________ RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control Pin Configurations (continued) TOP VIEW RO 1 RE 2 VREG 3 + 8 7 VCC B A GND RO DE/RE VREG 1 2 3 + 8 7 VCC B A GND MAX13410E–MAX13415E MAX13412E MAX13413E *EP 6 5 MAX13414E MAX13415E *EP 6 5 DI 4 DI 4 SO *EXPOSED PAD CONNECTED TO GROUND SO Ordering Information/Selector Guide (continued) PART MAX13412EESA+ MAX13413EESA+ MAX13414EESA+** MAX13415EESA+** PIN-PACKAGE 8 SO-EP* 8 SO-EP* 8 SO-EP* 8 SO-EP* AutoDirection Yes Yes No No DATA RATE (max) 500kbps 16Mbps 500kbps 16Mbps 5V LDO OUTPUT Yes Yes Yes Yes Note: All devices operate over the -40°C to +85°C operating temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. **Future product—contact factory for availability. Chip Information PROCESS TECHNOLOGY: BiCMOS Package Information For the latest package outline information and land patterns, go to www.maxim-ic.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. PACKAGE TYPE 8 SO-EP PACKAGE CODE S8E+14 DOCUMENT NO. 21-0111 ______________________________________________________________________________________ 23 RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control MAX13410E–MAX13415E Revision History REVISION NUMBER 0 1 REVISION DATE 11/07 8/09 Initial release. Replaced Figure 9. DESCRIPTION PAGES CHANGED — 20 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. 24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.