MAX1486EUB+T

19-1312; Rev 1; 3/06 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package The MAX1481/MAX1484 are functionally equivalent to the industry-standard MAX491 and 75180, and are designed for space-constrained, full-duplex RS-422 applications. All parts contain one driver and one receiver and feature a 1/8-unit-load receiver input impedance, allowing up to 256 transceivers on the bus. The MAX1481/ MAX1485 feature reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 250kbps. The MAX1484/MAX1486 driver slew rates are not limited, allowing them to transmit up to 12Mbps. The MAX1481/MAX1484/MAX1485/MAX1486 draw only 300µA of supply current. The MAX1481 has a low-power shutdown mode that reduces supply current to only 0.1µA. All devices operate from a single 5V supply. Drivers are output short-circuit current limited and are protected against excessive power dissipation by thermal-shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a failsafe feature that guarantees a logic-high output if the input is open circuit. ____________________________Features ♦ 10-Pin µMAX Package: Smallest 10-Pin Package ♦ Software-Selectable Half-/Full-Duplex Operation (MAX1485/MAX1486) ♦ 0.1µA Low-Current Shutdown Mode (MAX1481) ♦ Slew-Rate Limiting Allows Error-Free Data Transmission (MAX1481/MAX1485) ♦ 12Mbps High-Speed Operation (MAX1484/MAX1486) ♦ Allow up to 256 Transceivers on the Bus ______________Ordering Information PART TEMP RANGE PIN-PACKAGE MAX1481CUB 0°C to +70°C 10 µMAX MAX1481EUB MAX1484CUB MAX1484EUB MAX1485CUB -40°C to +85°C 0°C to +70°C -40°C to +85°C 0°C to +70°C 10 µMAX 10 µMAX 10 µMAX 10 µMAX MAX1485EUB MAX1486CUB MAX1486EUB -40°C to +85°C 0°C to +70°C -40°C to +85°C 10 µMAX 10 µMAX 10 µMAX ________________________Applications Low-Power RS-422/RS-485 Communications Level Translators Hand-Held Equipment Battery-Powered Equipment Transceiver for EMI-Sensitive Applications Industrial-Control Local Area Networks µMAX is a registered trademark of Maxim Integrated Products, Inc. ______________________________________________________________Selection Table Part Half/Full Duplex Data Rate (Mbps) SlewRate Limited LowPower Shutdown Driver Enable Receiver Enable Quiescent Current (µA) Transceivers on Bus PinPackage MAX1481 Full 0.250 Yes Yes Yes Yes 300 256 10 µMAX MAX1484 Full 12 No No Yes Yes 300 256 10 µMAX MAX1485 Selectable 0.250 Yes No Yes No 300 256 10 µMAX MAX1486 Selectable 12 No No Yes No 300 256 10 µMAX ________________________________________________________________ Maxim Integrated Products 1 ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at For small orders, phone 408-737-7600 ext. 3468. 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX1481/MAX1484/MAX1485/MAX1486 _______________General Description The MAX1481/MAX1484/MAX1485/MAX1486 provide software-selectable, half-/full-duplex, low-power, slewrate-limited, and high-speed (12Mbps) RS-485/RS-422 operation in a 10-pin µMAX ® package—the smallest 10-pin package available. The software-selectable, half-/full-duplex MAX1485/ MAX1486 make obsolete the normally larger and more expensive solutions required for selectable half-/fullduplex RS-485/RS-422 operation: 1) a 14-pin, fullduplex transceiver configured via jumpers between receiver and transmitter lines, or 2) two 8-pin, halfduplex transceivers, which require an additional inverter logic gate for software selectability. MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC) ............................................................+7V Control Input Voltage (RE, DE, H/F) ...........-0.3V to (VCC + 0.3V) Driver Input Voltage (DI).............................-0.3V to (VCC + 0.3V) Driver Output Voltage (A, B, Y, Z) ..........................-8V to +12.5V Receiver Input Voltage, Half Duplex (Y, Z) ............-8V to +12.5V Receiver Input Voltage, Full Duplex (A, B).............-8V to +12.5V Receiver Output Voltage (RO)....................-0.3V to (VCC + 0.3V) Continuous Power Dissipation 10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW Operating Temperature Ranges MAX148_C_ _ ......................................................0°C to +70°C MAX148_E_ _....................................................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+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 ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DRIVER VOD1 Differential Driver Output Change in Magnitude of Differential Output Voltage (Note 2) VOD2 No load, Figure 5 5 R = 50Ω (RS-422), Figure 5 2.0 R = 27Ω (RS-485), Figure 5 1.5 V 5 ∆VOD R = 50Ω or 27Ω, Figure 5 0.2 V VOC R = 50Ω or 27Ω, Figure 5 3 V Change in Magnitude of Common-Mode Voltage (Note 2) ∆VOC R = 50Ω or 27Ω, Figure 5 0.2 V Input High Voltage VIH1 DE, DI, RE, H/F Input Low Voltage VIL1 DE, DI, RE, H/F Input Current IIN1 DE, DI, RE, H/F Driver Common-Mode Output Voltage Input Current (Y and Z for Half Duplex, A and B for Full Duplex) IIN2 DE = GND, VCC = GND or 5.25V Output Leakage (Y and Z) (MAX1481/MAX1484 Only) IO DE = GND Output Leakage (Y and Z) (MAX1485/MAX1486 Only) IO DE = GND Driver Output Short-Circuit Current (Note 3) IOSD 2 -7V ≤ VOUT ≤ 12V 2.0 V 0.8 V ±2 µA VIN = 12V 0.125 VIN = -7V -0.1 VIN = 12V 10 VIN = -7V -10 VIN = 12V 125 VIN = -7V -100 35 _______________________________________________________________________________________ 250 mA µA µA mA Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 200 mV RECEIVER Receiver Differential Threshold Voltage VTH -7V ≤ VCM ≤ 12V -200 Receiver Input Hysteresis ∆VTH Receiver Output High Voltage VOH IO = -4mA, VID = 200mV Receiver Output Low Voltage VOL IO = 4mA, VID = -200mV 0.4 V Three-State Output Current at Receiver IOZR 0.4V ≤ VO ≤ 2.4V ±1 µA Receiver Input Resistance RIN -7V ≤ VCM ≤ 12V Receiver Output Short-Circuit Current IOSR 0V ≤ VRO ≤ VCC ICC RE = GND, DE = VCC ISHDN DE = GND, RE = VCC 70 mV 3.5 V 96 kΩ ±95 mA 300 600 µA 0.1 10 µA TYP MAX UNITS 30 60 30 60 5 10 ns 15 35 ns SUPPLY CURRENT No-Load Supply Current Supply Current in Shutdown Mode (MAX1481 Only) SWITCHING CHARACTERISTICS (MAX1484/MAX1486) (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER Driver Input to Output Driver Input to Output SYMBOL tDPLH tDPHL CONDITIONS MIN RDIFF = 54Ω, CL1 = CL2 = 100pF, Figures 7 and 9 Driver Output Skew | tDPLH - tDPHL | tDSKEW RDIFF = 54Ω, CL1 = CL2 = 100pF, Figures 7 and 9 Driver Rise or Fall Time tDR, tDF RDIFF = 54Ω, CL1 = CL2 = 100pF, Figures 7 and 9 5 12 ns Maximum Data Rate fMAX Driver Enable to Output Low tDZL CL = 100pF, S1 closed, Figures 8 and 10 40 70 Mbps ns Driver Enable to Output High tDZH CL = 100pF, S2 closed, Figures 8 and 10 40 70 ns Driver Disable Time from Low tDLZ CL = 15pF, S1 closed, Figures 8 and 10 40 70 ns Driver Disable Time from High tDHZ CL = 15pF, S2 closed, Figures 8 and 10 40 70 ns 150 ns Receiver Input to Output tRPLH, tRPHL Figures 11 and 13 90 | tRPLH - tRPHL | Differential Receiver Skew tRSKD Figures 11 and 13 5 ns Receiver Enable to Output Low tRZL CL = 100pF, S1 closed, Figures 6 and 12 20 50 ns Receiver Enable to Output High tRZH CL = 100pF, S2 closed, Figures 6 and 12 20 50 ns Receiver Disable Time from Low tRLZ CL = 100pF, S1 closed, Figures 6 and 12 20 50 ns Receiver Disable Time from High tRHZ CL = 100pF, S2 closed, Figures 6 and 12 20 50 ns _______________________________________________________________________________________ 3 MAX1481/MAX1484/MAX1485/MAX1486 ELECTRICAL CHARACTERISTICS (continued) MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package SWITCHING CHARACTERISTICS (MAX1481/MAX1485) (continued) (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER Driver Input to Output SYMBOL tDPLH tDPHL CONDITIONS MIN RDIFF = 54Ω, CL1 = CL2 = 100pF, Figures 7 and 9 Driver Output Skew | tDPLH - tDPHL | tDSKEW RDIFF = 54Ω, CL1 = CL2 = 100pF, Figures 7 and 9 Driver Rise or Fall Time tDR, tDF RDIFF = 54Ω, CL1 = CL2 = 100pF, Figures 7 and 9 TYP MAX 600 1000 600 1000 10 200 ns 1000 ns 250 250 UNITS ns Maximum Data Rate fMAX Driver Enable to Output Low tDZL CL = 100pF, S1 closed, Figures 8 and 10 3000 kbps ns Driver Enable to Output High tDZH CL = 100pF, S2 closed, Figures 8 and 10 3000 ns Driver Disable Time from Low tDLZ CL = 15pF, S1 closed, Figures 8 and 10 200 ns Driver Disable Time from High tDHZ CL = 15pF, S2 closed, Figures 8 and 10 200 ns 150 ns Receiver Input to Output tRPLH, tRPHL Figures 11 and 13 90 | tRPLH - tRPHL | Differential Receiver Skew tRSKD Figures 11 and 13 15 ns Receiver Enable to Output Low tRZL CL = 100pF, S1 closed, Figures 6 and 12 20 50 ns Receiver Enable to Output High tRZH CL = 100pF, S2 closed, Figures 6 and 12 20 50 ns Receiver Disable Time from Low tRLZ CL = 100pF, S1 closed, Figures 6 and 12 20 50 ns tRHZ CL = 100pF, S2 closed, Figures 6 and 12 20 50 ns 200 600 ns Receiver Disable Time from High Time to Shutdown tSHDN MAX1481 only (Note 4) 50 Driver Enable from Shutdown to Output High tDZH(SHDN) MAX1481 only, CL = 15pF, S2 closed, Figures 8 and 10 3000 ns Driver Enable from Shutdown to Output Low tDZL(SHDN) MAX1481 only, CL = 15pF, S1 closed, Figures 8 and 10 3000 ns Receiver Enable from Shutdown to Output High tRZH(SHDN) MAX1481 only, CL = 100pF, S2 closed, Figures 6 and 12 500 ns Receiver Enable from Shutdown to Output Low tRZL(SHDN) MAX1481 only, CL = 100pF, S1 closed, Figures 6 and 12 1000 ns Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referenced to device ground unless otherwise noted. Note 2: ∆VOD and ∆VOC are the changes in VOD and VOC, respectively, when the DI input changes state. Note 3: Maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during current limiting. Note 4: Shutdown is enabled by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the MAX1481 is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 600ns, the MAX1481 is guaranteed to have entered shutdown. 4 _______________________________________________________________________________________ Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package 300 280 MAX1484/MAX1486 260 40 30 20 220 -20 0 20 40 60 80 100 2 3 4 5 2 3 4 5 OUTPUT LOW VOLTAGE (V) SHUTDOWN CURRENT vs. TEMPERATURE RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE IRO = 8mA 0.45 0.40 IRO = 8mA 4.4 OUTPUT VOLTAGE (V) 102 4.5 MAX1481/4/5/6-05 MAX1481/4/5/6-04 106 0.50 98 0.35 0.30 0.25 0.20 94 0 20 40 60 80 100 4.2 4.1 4.0 3.8 0.10 -20 4.3 3.9 0.15 -60 -40 -20 0 20 40 60 80 -60 100 -40 -20 0 20 40 60 80 100 MAX1481/MAX1485 RECEIVER PROPAGATION DELAY vs. TEMPERATURE MAX1484/MAX1486 RECEIVER PROPAGATION DELAY vs. TEMPERATURE MAX1481/MAX1485 DRIVER PROPAGATION DELAY vs. TEMPERATURE 95 90 85 80 CLOAD = 15pF 93 92 91 90 89 88 86 -60 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 100 RDIFF = 54Ω CL1 = CL2 = 100pF 660 640 620 600 580 560 87 75 680 PROPAGATION DELAY (ns) 100 94 PROPAGATION DELAY (ns) CLOAD = 15pF MAX1481/4/5/6-09 TEMPERATURE (°C) MAX1481/4/5/6-08 TEMPERATURE (°C) MAX1481/4/5/6-07 TEMPERATURE (°C) 105 PROPAGATION DELAY (ns) 1 0 OUTPUT LOW VOLTAGE (V) 110 -40 10 TEMPERATURE (°C) 114 -60 15 0 1 0 OUTPUT LOW VOLTAGE (V) -40 20 5 0 -60 MAX1481/4/5/6-03 25 10 240 SHUTDOWN CURRENT (nA) MAX1481/4/5/6-02 50 30 MAX1481/4/5/6-06 320 OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE 60 OUTPUT CURRENT (mA) MAX1481/MAX1485 340 SUPPLY CURRENT (µA) MAX1481/4/5/6-01 360 OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE OUTPUT CURRENT (mA) NO-LOAD SUPPLY CURRENT vs. TEMPERATURE 540 -60 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 100 -60 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX1481/MAX1484/MAX1485/MAX1486 __________________________________________Typical Operating Characteristics (VCC = +5V, TA = +25°C, unless otherwise noted.) _________________________________Typical Operating Characteristics (continued) (VCC = +5V, TA = +25°C, unless otherwise noted.) 30 26 120 100 80 60 40 22 -40 -20 0 20 40 60 80 100 80 60 40 0 0 0 2 4 6 8 10 -8 12 -6 -4 -2 0 2 4 TEMPERATURE (°C) OUTPUT LOW VOLTAGE (V) OUTPUT HIGH VOLTAGE (V) DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE MAX1484/MAX1486 RECEIVER PROPAGATION DELAY RDIFF = 54Ω 2.35 2.30 2.25 2.20 6 MAX1481/4/5/6-15 100 MAX1481/4/5/6-14 MAX1481/4/5/6-13 2.40 OUTPUT CURRENT (mA) -60 100 20 20 18 120 MAX1481/4/5/6-12 34 140 MAX1481/4/5/6-11 PROPAGATION DELAY (ns) RDIFF = 54Ω CL1 = CL2 = 100pF OUTPUT CURRENT (mA) MAX1481/4/5/6-10 38 OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE OUTPUT CURRENT (mA) MAX1484/MAX1486 DRIVER PROPAGATION DELAY vs. TEMPERATURE OUTPUT VOLTAGE (V) MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package 10 VA - VB (2V/div) 1 RO (5V/div) 0.1 2.15 2.10 0.01 -60 -40 -20 0 20 40 60 80 100 0 DIFFERENTIAL OUTPUT VOLTAGE (V) MAX1481/MAX1485 RECEIVER PROPAGATION DELAY MAX1481/MAX1485 DRIVER PROPAGATION DELAY RO (5V/div) 1µs/div 6 MAX1484/MAX1486 DRIVER PROPAGATION DELAY MAX1481/4/5/6-18 MAX1481/4/5/6-17 MAX1481/4/5/6-16 VA - VB (2V/div) 50ns/div 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 TEMPERATURE (°C) DI (5V/div) DI 5V/div VY - VZ (2V/div) VY - VZ 2V/div 1µs/div 50ns/div _______________________________________________________________________________________ Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package PIN PIN MAX1481/ MAX1484 MAX1485/MAX1486 NAME FUNCTION H/F = 0 H/F = 1 1 1 1 RO Receiver Output. When RE is low and if A - B ≥ 200mV, RO goes high; if A - B ≤ -200mV, RO goes low. — 2 2 H/F Half-/Full-Duplex Selector Input. Connect H/F to VCC for half-duplex mode, and connect to GND for full-duplex mode. 2 — — RE Receiver Output Enable Input. Drive RE low to enable RO; RO is high impedance when RE is high. For MAX1481 only, drive RE high and DE low to enter the lowpower shutdown mode. 3 3 3 DE Driver Output Enable Input. Drive DE high to enable driver outputs. These outputs are high impedance when DE is low. 4 4 4 DI Driver Input. With DE high, a low on DI forces noninverting output low and inverting output high. Similarly, a high on DI forces noninverting output high and inverting output low. 5 5 5 GND 6 6 — B Inverting Receiver Input — — 6 B Receiver Input Resistors* 7 7 — Z Inverting Driver Output — — 7 Z Inverting Driver Output and Inverting Receiver Input 8 8 — Y Noninverting Driver Output — — 8 Y Noninverting Driver Output and Noninverting Receiver Input Ground 9 9 — A Noninverting Receiver Input — — 9 A Receiver Input Resistors* 10 10 10 VCC Positive Supply; +4.75V ≤ VCC ≤ +5.25V *(MAX1485/MAX1486 only) In half-duplex mode, the driver outputs serve as receiver inputs. The full-duplex receiver inputs (A and B) will still have a 1/8-unit load, but are not connected to the receiver. _______________________________________________________________________________________ 7 MAX1481/MAX1484/MAX1485/MAX1486 ______________________________________________________________Pin Description MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package _____________________________________________________________Function Tables MAX1481 RECEIVING TRANSMITTING INPUTS INPUTS OUTPUTS OUTPUT RE DE DI Z Y RE DE A-B RO X 1 1 0 1 0 X ≥ 0.2V 1 X 1 0 1 0 0 X ≤ -0.2V 0 0 0 X High-Z High-Z 1 1 X High-Z 1 0 X 1 0 X High-Z and Shutdown High-Z and Shutdown MAX1484 TRANSMITTING RECEIVING INPUTS OUTPUTS INPUTS OUTPUT RE DE DI Z Y RE DE A-B RO X 1 1 0 1 0 X ≥ 0.2V 1 X 1 0 1 0 0 X ≤ -0.2V 0 X 0 X High-Z High-Z 1 X X High-Z MAX1485/MAX1486 TRANSMITTING INPUTSINPUTS RECEIVING OUTPUTS INPUTS DE DI Z Y H/F DE 1 1 0 1 0 1 0 1 0 0 0 X High-Z High-Z OUTPUT OUTPUT A-B Y-Z RO X ≥ 0.2V X 1 X ≤ -0.2V X 0 1 0 X ≥ 0.2V 1 1 0 X ≤ -0.2V 0 X = Don’t care Note: In shutdown mode, driver and receiver outputs are high impedance. 8 _______________________________________________________________________________________ Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package MAX1481 MAX1484 RO 1 MAX1481 MAX1484 0.1µF MAX1481 MAX1484 10 VCC RE 2 9 A DE 3 8 Y DI 4 7 Z GND 5 6 B RO RE DE DI 1 10 VCC 9 A 0.1µF Rt Y 8 7 Z 6 B 2 10 VCC Rt 7 Z 8 Y 5 µMAX B 6 9 A 1 5 GND 4 DI 3 DE 2 RE 3 4 MAX1481/MAX1484/MAX1485/MAX1486 TOP VIEW RO GND Figure 1. MAX1481/MAX1484 Pin Configuration and Typical Full-Duplex Operating Circuit MAX1485 MAX1486 TOP VIEW MAX1485 MAX1486 0.1µF 0.1µF 10 RO 1 10 VCC RO 9 A H/F 2 8 Y H/F 2 DE 3 DI 4 7 Z GND 5 6 B MAX1485 MAX1486 1 DE DI VCC 9 A Rt Y 8 7 Z 6 B 10 CC VCC DI 3 DE 2 H/F 3 Rt 7 Z 4 8 Y 5 µMAX B 6 9 A 1 5 GND 4 RO GND Figure 2. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Full-Duplex Operating Circuit MAX1485 MAX1486 TOP VIEW MAX1485 MAX1486 0.1µF 10 VCC RO 1 H/F 2 DE 3 MAX1485 MAX1486 9 A 8 Y DI 4 7 Z GND 5 6 B µMAX RO 1 10 VCC DI 10 VCC 8 Y H/F 2 DE 0.1µF Rt Rt 3 7 Z Z 7 4 9 A A 9 6 B B 6 5 GND 4 DI 3 DE 2 H/F Y 8 1 5 RO GND Figure 3. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Half-Duplex Operating Circuit _______________________________________________________________________________________ 9 MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package MAX1485/MAX1486 Half-/Full-Duplex Mode Operation VCC DI MAX1485 MAX1486 Z Y DE The MAX1484/MAX1485 can operate in full- or halfduplex mode. Drive the H/F pin low or connect it to GND for full-duplex operation, or drive it high for halfduplex operation. In full-duplex mode, the pin configuration of the driver and receiver is the same as a MAX1481 (Figure 1). __________Applications Information RO 256 Transceivers on the Bus H/F B A GND Figure 4. MAX1485/MAX1486 Functional Diagram _______________Detailed Description The MAX1481/MAX1484/MAX1485/MAX1486 highspeed transceivers for RS-485/RS-422 communication contain one driver and one receiver. The MAX1481/ MAX1485 feature reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 250kbps. The MAX1484/MAX1486 driver slew rates are not limited, making transmission speeds up to 12Mbps possible. These transceivers are designed to operate on a +5V single supply and typically draw 300µA of supply current when unloaded or fully loaded with the drivers disabled. The MAX1481 has a shutdown mode in which supply current is typically reduced to 0.1µA. Drivers are output short-circuit current limited and are protected against excessive power dissipation by thermal-shutdown circuitry that places the driver outputs into a high-impedance state. All devices have a 1/8-unit-load receiver input impedance that allows up to 256 transceivers on the bus. The MAX1481/MAX1484 are designed for full-duplex communications. The H/F pin on the MAX1485/MAX1486 allows the user to select between half-duplex or fullduplex operation (Figure 4). 10 The standard RS-485 receiver input impedance is 12kΩ (1-unit load), and the standard driver can drive up to 32-unit loads. The MAX1481/MAX1484/MAX1485/ MAX1486 transceivers have a 1/8-unit-load receiver input impedance (96kΩ), allowing up to 256 transceivers to be connected in parallel on one communication line. Connect any combination of these devices and/or other RS-485 transceivers totaling 32-unit loads or less. Reduced EMI and Reflections The MAX1481/MAX1485 are slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 14 shows the driver output waveform and its Fourier analysis of a 20kHz signal transmitted by a MAX1484. High-frequency harmonic components with large amplitudes are evident. Figure 15 shows the same signal displayed for a MAX1481 transmitting under the same conditions. Figure 15’s high-frequency harmonic components are much lower in amplitude compared to Figure 14’s, significantly reducing potential EMI. In general, a transmitter’s rise time relates directly to the length of an unterminated stub, which can be driven with only minor waveform reflections. The following equation expresses this relationship conservatively: Length = tRISE / (10 x 1.5ns/ft) where tRISE is the transmitter’s rise time. For example, the MAX1481’s rise time is typically 500ns, which results in excellent waveforms with a stub length up to 33 feet. A system may work well with longer unterminated stubs, even with severe reflections, if the waveform settles out before the UART samples them. ______________________________________________________________________________________ Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package MAX1481/MAX1484/MAX1485/MAX1486 Y R RECEIVER OUTPUT VOD 1k TEST POINT VCC S1 CL R 1k VOC S2 Z Figure 5. Driver DC Test Load Figure 6. Receiver Enable/Disable Timing Test Load 3V DE CL1 Y DI RDIFF VID VCC S1 500Ω OUTPUT UNDER TEST Z CL CL2 S2 Figure 7. Driver Timing Test Circuit Figure 8. Driver Enable/Disable Timing Test Load 3V DI 1.5V 0V 3V 1.5V tDPHL tDPLH DE 1/2 VO 1.5V tDZL(SHDN), tDPL Z tDLZ Y, Z VO Y VOL 1/2 VO VO VDIFF 0V -VO 1.5V 0V 10% 2.3V OUTPUT NORMALLY LOW VDIFF = VY - VZ 90% 90% tR tF tSKEW = | tPLH - tPHL | Figure 9. Driver Propagation Delays OUTPUT NORMALLY HIGH Y, Z 10% VOL +0.5V VOH -0.5V 2.3V 0V DZH(SHDN), DZH DHZ Figure 10. Driver Enable and Disable Times ______________________________________________________________________________________ 11 3V RE 1.5V 1.5V 0V RO VOH 1.5V VOL 1V A -1V B RPHL RZL(SHDN), RZL 1.5V OUTPUT RPLH RLZ VCC RO 1.5V OUTPUT NORMALLY LOW RO 1.5V INPUT VOL + 0.5V OUTPUT NORMALLY HIGH VOH - 0.5V 0V RZH(SHDN), RZH Figure 11. Receiver Propagation Delays RHZ Figure 12. Receiver Enable and Disable Times (MAX1481/MAX1484 only) MAX1481/4/5/6-fig14 MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package B ATE VID RR RECEIVER OUTPUT 20dB/div A 0Hz Figure 13. Receiver Propagation Delay Test Circuit Low-Power Shutdown Mode (MAX1481 only) Low-power shutdown mode is initiated by bringing both RE high and DE low. In shutdown, the MAX1481 typically draws only 0.1µA of supply current. RE and DE may be driven simultaneously; the parts are guaranteed not to enter shutdown if RE is high and DE is low for less than 50ns. If the inputs are in this state for at least 600ns, the parts are guaranteed to enter shutdown. Enable times t_ZH and t_ZL in the Switching Characteristics tables assume the part was not in low-power shutdown. Enable times t_ZH(SHDN) and t_ZL(SHDN) assume the parts were shut down. It takes drivers and receivers 12 250kHz/div 2.5MHz Figure 14. Driver Output Waveform and FFT Plot of MAX1484/MAX1486 Transmitting a 20kHz signal longer to become enabled from the low-power shutdown mode (t_ ZH (SHDN) , t_ Z L(SHDN) ) than from the driver/receiver disable mode (t_ZH, t_ZL). Driver Output Protection Excessive output current and power dissipation caused by faults or by bus contention are prevented by two mechanisms. A foldback current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range (see Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature becomes excessive. ______________________________________________________________________________________ Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package Figures 17 and 18 show the system differential voltage for the parts driving 4000 feet of 26AWG twisted-pair wire into 120Ω loads. Typical Applications 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 MAX1481/MAX1485 are more tolerant of imperfect termination than the MAX1484/MAX1486. MAX1481/4/5/6-fig15 The MAX1485/MAX1486 are designed for bidirectional data communications on multipoint bus transmission lines. Figures 19 and 20 show typical network applications circuits. These parts can also be used as line repeaters with cable lengths longer than 4000 feet (Figure 16). MAX1481 MAX1484 MAX1485 MAX1486 A RO RE R 120Ω B DATA IN DE 20dB/div Z DI D H/F 0Hz 250kHz/div 2.5MHz Figure 15. Driver Output Waveform and FFT Plot of MAX1481/MAX1485 Transmitting a 20kHz Signal 120Ω Y DATA OUT NOTE: RE ON MAX1481 AND MAX1484 ONLY. H/F ON MAX1485 AND MAX1486 ONLY. Figure 16. Line Repeater MAX1481/4/5/6-fig18 MAX1481/4/5/6-fig17 DI 5V/div DI 5V/div VA - VB 4V/div VA - VB 4V/div RO 5V/div RO 5V/div 5µs/div Figure 17. MAX1481/MAX1485 System Differential Voltage at 50kHz Driving 4000 ft. of Unterminated Cable 1µs/div Figure 18. MAX1484/MAX1486 System Differential Voltage at 200kHz Driving 4000 ft. of Unterminated Cable ______________________________________________________________________________________ 13 MAX1481/MAX1484/MAX1485/MAX1486 Line Length vs. Data Rate The RS-485/RS-422 standard covers line lengths up to 4000 feet. For line lengths greater than 4000 feet, use the repeater application shown in Figure 16. MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package 5V VCC 5V H/F 120Ω H/F DE (Z) Z DI VCC 120Ω D D DI DE RO Y Z Y Z R (Y) Y R 5V R H/F R VCC D D VCC VCC MAX1485 MAX1486 DI DE RO DI DE RO Figure 19. Typical Half-Duplex RS-485 Network 14 ______________________________________________________________________________________ RO Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package Y 120Ω R RO RE 120Ω D B Z Z B DI DE DI MAX1481/MAX1484/MAX1485/MAX1486 A DE 120Ω D Y 120Ω Z Y B A Y Z B A RE* RO R A H/F** H/F** R D DI R H/F** DE RE* RO H/F** D DI DE RE* RO MAX1481 MAX1484 MAX1485 MAX1486 *RE ON MAX1481 AND MAX1484 ONLY. **H/F ON MAX1485 AND MAX1486 ONLY. Figure 20. Typical Full-Duplex RS-485 Network ___________________Chip Information TRANSISTOR COUNT: 396 ______________________________________________________________________________________ 15 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) ________________________________________________________Package Information 10LUMAXB.EPS MAX1481/MAX1484/MAX1485/MAX1486 Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2006 Maxim Integrated Products PrintedSA is a registered trademark of Maxim Integrated Products, Inc.