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Download MAX485 Low Power, Slew-Rate-Limited RS-485/RS
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MAX485 MAX485 Low Power, Slew-Rate-Limited RS-485/RS-422 Transceiver DESCRIPTION The MAX485 is low-power transceivers for RS-485 and RS-422 communication. IC contains one driver and one receiver. The driver slew rates of the MAX485 is not limited, allowing them to transmit up to 2.5Mbps. These transceivers draw between 120µA and 500µA of supply current when unloaded or fully loaded with disabled drivers. All parts operate from a single 5V supply. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The MAX485 is designed for half-duplex applications FEATURES APPLICATIONS Low Quiescent Current: 300µA -7V to +12V Common-Mode Input Voltage Range Three-State Outputs 30ns Propagation Delays, 5ns Skew Full-Duplex and Half-Duplex Versions Available Operate from a Single 5V Supply Allows up to 32 Transceivers on the Bus Data rate: 2,5 Mbps Current-Limiting and Thermal Shutdown for Driver Overload Protection Low-Power RS-485 Transceivers Low-Power RS-422 Transceivers Level Translators Transceivers for EMI-Sensitive Applications Industrial-Control Local Area Networks ORDERING INFORMATION PART NO. MAX485CPA MAX485CSA MAX485EPA MAX485ESA Temp. Range (°C) 0 to 70 0 to 70 -40 to 85 -40 to 85 PINOUT Package 8 Pin DIP 8 Pin SOP 8 Pin DIP 8 Pin SOP TYPICAL APPLICATION TOP VIEW RO1 RO 1 R RE 2 DE 3 DI 4 D 8 VCC 7 B 6 A 5 GND R VCC1 RE1 Rt DE1 DI1 D GND1 DIP8 / SOP8 Rt RO2 R VCC2 RE2 DE2 DI2 1 D GND2 MAX485 PIN DESCRIPTIONS Pin No. PIN NAME 01 RO 02 RE 03 DE 04 DI 05 06 07 08 GND A B Vcc DESCRIPTION Receiver Output. If the receiver output is enabled(RE low), then if A > B by 200mV, RO will be high. If A < B by 200mV, then RO will be low. Receiver Output Enable. A low enables the receiver output, RO. A high input forces the receiver output into a high impedance state. Driver Outputs Enable. A high on DE enables the driver output. A and B, and the chip will function as a line driver. A low input will force the driver outputs into a high impedance state and the chip will function as a line receiver. Driver Input. If the driver outputs are enabled (DE high), then a low on DI forces the outputs A low and B high. A high on DI with the driver outputs enabled will force A high and B low. Ground Connection. Driver Output/Receiver Input. Driver Output/Receiver Input. Positive Supply; 4.75 < Vcc < 5.25. ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC) …………………………………………………………………………..…..12V Control Input Voltage………………………………………………………......-0.5V to (VCC +0.5V) Driver Input Voltage (DI)………………………………………………………-0.5V to (VCC +0.5V) Driver Output Voltage (A, B)………………………………………………………..… -8V to +12.5V Receiver Input Voltage (A, B)…………………………………………………………. -8V to +12.5V Receiver Output Voltage (RO)…………………………………………….…-0.5V to (VCC +0.5V) Continuous Power Dissipation…………………………………………………………. (TA= +70°C) 8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) …………………………….………..727mW 8-Pin SO (derate 5.88mW/°C above +70°C) ………………………………………………471mW Storage Temperature Range………………………………………………….……-65°C to +160°C Lead Temperature (soldering, 10sec)……………………………………………….……… +300°C DC ELECTRICAL CHARACTERISTICS (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2) PARAMETER Differential Driver Output (no load) Differential Driver Output (with load) SYMBOL VOD1 VOD2 Change in Magnitude of Driver Differential Output Voltage for Complementary Output States Driver Common-Mode Output Voltage Change in Magnitude of Driver Common-Mode Output Voltage for Complementary Output States Input High Voltage Input Low Voltage Input Current Input Current (A, B) ∆VOD Receiver Differential Threshold Voltage Receiver Input Hysteresis Receiver Output High Voltage Receiver Output Low Voltage VTH CONDITIONS R = 50Ω (RS-422) R = 27Ω (RS-485), Figure 4 R = 27Ω or 50Ω, Figure 4 MIN TYP 2 1.5 MAX UNITS 5 V V 5 0.2 V VOC R = 27Ω or 50Ω, Figure 4 3 V ∆VOD R = 27Ω or 50Ω, Figure 4 0.2 V VIH VIL IIN1 IIN2 ∆VTH VOH VOL DE, DI, RE DE, DI, RE DE, DI, RE DE = 0V; VCC = 0V or 5.25V, -7V ≤ VCM ≤12V 2.0 VIN = 12V VIN = -7V VCM = 0V IO = -4mA, VID = 200mV IO = 4mA, VID = -200mV 2 0.8 ±2 1.0 -0.8 0.2 -0.2 70 3.5 0.4 V V µA mA V mV V V MAX485 DC ELECTRICAL CHARACTERISTICS (continued) (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2) PARAMETER SYMBOL Three-State (high impedance) Output Current at Receiver Receiver Input Resistance No-Load Supply Current (Note 3) IOZR 0.4V ≤ VO ≤ 2.4V RIN ICC -7V ≤ VCM ≤ 12V Driver Short-Circuit Current, VO = High Driver Short-Circuit Current, VO = Low Receiver Short-Circuit Current CONDITIONS RE = 0V or VCC MIN TYP MAX UNITS ±1 µA kΩ 12 DE = VCC DE = 0V IOSD1 -7V ≤ VO ≤ 12V (Note 4) IOSD2 -7V ≤ VO ≤ 12V (Note 4) IOSR 0V ≤ VO ≤ VCC 500 300 900 500 µA 35 250 mA 35 250 mA 7 95 mA SWITCHING CHARACTERISTICS (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2) PARAMETER Driver Input to Output Driver Output Skew to Output Driver Enable to Output High Driver Enable to Output Low Driver Disable Time from Low Driver Disable Time from High | tPLH - tPHL | Differential Receiver Skew Receiver Enable to Output Low Receiver Enable to Output High Receiver Disable Time from Low Receiver Disable Time from High Maximum Data Rate SYMBOL MIN TYP MAX UNITS 10 30 60 ns 10 60 10 ns tZH tZL tLZ tHZ RDIFF = 54Ω, CL1 = CL2 = 100pF CL= 100pF, S2 closed CL= 100pF, S1 closed CL= 15pF, S1 closed CL= 15pF, S2 closed 30 5 40 40 40 40 70 70 70 70 ns ns ns ns tSKD RDIFF = 54Ω 13 tZL tZH tLZ CRL = 15pF, S1 closed CRL = 15pF, S2 closed CRL = 15pF, S1 closed 20 20 20 50 50 50 ns ns ns tHZ CRL = 15pF, S2 closed 20 50 ns tPLH tPHL tSKEW CONDITIONS RDIFF = 54Ω CL1 = CL2 = 100pF fMAX 2.5 ns Mbps Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device ground unless otherwise specified. Note 2: All typical specifications are given for VCC = 5V and TA = +25°C. Note 3: Supply current specification is valid for loaded transmitters when DE = 0V. Note 4: Applies to peak current. See Typical Operating Characteristics. 3 MAX485 TESTING CIRCUITS A S1 TEST POINT R 1k RECEIVER OUTPUT VOD VCC CRL 15pF VOC R 1k S2 B Figure 1. Driver DC Test Load Figure 2. Receiver Timing Test Load 3V DE A DI S1 A CL1 RO RDIFF B B CL2 S2 RE CL 15pF Figure 3. Driver/Receiver Timing Test Circuit Figure 4. Driver Timing Test Load #2 SWITCHING TIME WAVEFORMS 3V f = 1MHz, t r ≤ 10ns, t f ≤ 10ns 1.5V DI 1.5V 0V t PLH 1/2 VO t PHL B VO A tSKEW 1/2 VO VO 0V –VO 80% 10% t SKEW 90% VDIFF = V(A) – V(B) 20% tr tf Figure 5. Driver Propagation Delays 3V 1.5V DE f = 1MHz, t r ≤ 10ns, t f ≤ 10ns 1.5V 0V 5V VCC 500Ω OUTPUT UNDER TEST t ZL A, B t LZ 2.3V OUTPUT NORMALLY LOW 0.5V 2.3V OUTPUT NORMALLY HIGH 0.5V VOL VOH A, B 0V t HZ t ZH Figure 6. Driver Enable and Disable Times 4 MAX485 SWITCHING TIME WAVEFORMS VOH 1.5V R f = 1MHz, t r ≤ 10ns, t f ≤ 10ns t PHL VOD2 A, B –VOD2 1.5V OUTPUT VOL 0V t PLH INPUT Figure 7. Receiver Propagation Delays 3V 1.5V RE f = 1MHz, t r ≤ 10ns, t f ≤ 10ns 1.5V 0V t ZL 5V t LZ R R 1.5V OUTPUT NORMALLY LOW 0.5V 1.5V OUTPUT NORMALLY HIGH 0.5V 0V t HZ t ZH Figure 8. Receiver Enable and Disable Times FUNCTION TABLES Transmitting Receiving INPUTS OUTPUTS INPUTS OUTPUTS RE DE DI LINE CONDITION B A RE DE A–B R X 1 1 No Fault 0 1 0 0 ≥ 0.2V 1 X 1 0 No Fault 1 0 0 0 ≤ – 0.2V 0 X 0 X X Z Z 0 0 Inputs Open 1 X 1 X Fault Z Z 1 0 X Z 5 MAX485 PACKAGE DIP8 Package (Narrow .300 Inch) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( 0.065 (1.651) TYP +0.035 0.325 –0.015 8.255 +0.889 –0.381 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) ) 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) 0.100 (2.54) BSC SOP8 Package (Narrow .150 Inch) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP 6 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC