19-2441; Rev 0; 4/02 ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection Applications Features ♦ ±60V Fault Protection ♦ ±15kV ESD Protection ♦ Guaranteed 10Mbps Data Rate ♦ Allows Up to 128 Transceivers on the Bus ♦ -7V to +12V Common-Mode Input Range ♦ True Fail-Safe Receiver Inputs ♦ Hot-Swap Inputs for Telecom Applications ♦ Automotive Temperature Range (-40°C to +125°C) ♦ Industry-Standard Pinout Ordering Information PART TEMP RANGE PIN-PACKAGE MAX3443ECSA 0°C to +70°C 8 SO MAX3443ECPA 0°C to +70°C 8 PDIP Industrial Networks MAX3443EESA -40°C to +85°C 8 SO Telecommunication Systems MAX3443EEPA -40°C to +85°C 8 PDIP Automotive Applications MAX3443EASA -40°C to +125°C 8 SO HVAC Controls MAX3443EAPA -40°C to +125°C 8 PDIP RS-422/RS-485 Communications Pin Configuration and Typical Operating Circuit TOP VIEW MAX3443E R 1 8 VCC RO RE 2 7 B RE 2 DE 3 6 A DE 3 DI 4 5 GND DI 4 RO 1 D DIP/SO R D 8 VCC 7 B Rt 6 A 5 GND DE D DI B Rt A RO R RE ________________________________________________________________ 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 MAX3443E General Description The MAX3443E fault-protected RS-485/RS-422 transceiver features ±60V protection from signal faults on communication bus lines. Each device contains one differential line driver with three-state output, and one differential line receiver with three-state input. The 1/4-unit-load receiver input impedance allows up to 128 transceivers on a single bus. The device operates from a 5V supply at data rates up to 10Mbps. True fail-safe inputs guarantee a logic-high receiver output when the receiver inputs are open, shorted, or connected to an idle data line. Hot-swap circuitry eliminates false transitions on the data cable during circuit initialization or connection to a live backplane. Short-circuit current limiting and thermal shutdown circuitry protect the driver against excessive power dissipation, and integrated ±15kV ESD protection eliminates costly external protection devices. The MAX3443E is available in 8-pin SO and PDIP packages, and is specified over commercial, industrial, and automotive temperature ranges. MAX3443E ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection ABSOLUTE MAXIMUM RATINGS All Voltages Referenced with Respect to GND VCC ........................................................................................+7V RE, DE, DI...................................................-0.3V to (VCC + 0.3V) A, B (Note 1) ........................................................................±60V RO ..............................................................-0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW 8-Pin PDIP (derate 9.09mW/°C above +70°C).............727mW Operating Temperature Ranges MAX3443EC_ _ ..................................................0°C to +70°C MAX3443EE_ _ ...............................................-40°C to +85°C MAX3443EA_ _ .............................................-40°C to +125°C Storage Temperature Range .............................-65°C to +150°C Short-Circuit Duration (RO, A, B) ...............................Continuous Lead Temperature (soldering, 10s) .................................+300°C Note 1: A, B must be terminated with 54Ω or 100Ω to guarantee ±60V fault protection. 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. DC ELECTRICAL CHARACTERISTICS (VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DRIVER Differential Driver Output Change in Magnitude of Differential Output Voltage Driver Common-Mode Output Voltage Change In Magnitude of Common-Mode Voltage VOD ∆VOD VOC ∆VOC Figure 1, RL = 50Ω 2.0 VCC Figure 1, RL = 27Ω 1.5 VCC Figure 1, RL = 50Ω or 27Ω (Note 2) Figure 1, RL = 50Ω or 27Ω VCC / 2 Figure 1, RL = 50Ω or 27Ω (Note 2) V 0.2 V 3 V 0.2 V DRIVER LOGIC Driver Input High Voltage VDIH 2.0 V Driver Input Low Voltage VDIL 0.8 V Driver Input Current IDIN ±2 µA Driver Output Fault Current IOFC VA, B = ±60V, RL = 54Ω ±6 mA Driver Short-Circuit Output Current IOSD -7V ≤ VOUT ≤ +12V (Note 3) ±350 mA Driver Short-Circuit Foldback Output Current IOSDF -7V ≤ VOUT ≤ +12V (Note 3) ±25 mA RECEIVER Input Current IA,B A, B DE = GND, VCC = GND, VA, B = +12V 250 VA, B = -7V -150 VA, B = ±60V Receiver Differential Threshold Voltage Receiver Input Hysteresis 2 VTH ∆VTH -7V ≤ VCM ≤ +12V -200 25 _______________________________________________________________________________________ µA ±6 mA -50 mV mV ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection MAX3443E DC ELECTRICAL CHARACTERISTICS (continued) (VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS RECEIVER LOGIC Output High Voltage VOH Figure 2, IOH = -1.6mA Output Low Voltage VOL Figure 2, IOL = 1mA VCC - 0.6 0.4 V V Three-State Output Current at Receiver IOZR 0 ≤ VA, B ≤ VCC ±1 µA Receiver Input Resistance RIN -7V ≤ VCM ≤ +12V Receiver Output Short-Circuit Current IOSR 0 ≤ VRO ≤ VCC VCIH DE, RE 48 kΩ ±95 mA CONTROL Control Input High Voltage 2.0 V Input Current DE Current Latch During First DE Rising Edge 90 µA Input Current RE Current Latch During First RE Falling Edge 90 µA PROTECTION SPECIFICATIONS (VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS A, B RSOURCE = 0, RL = 54Ω Overvoltage Protection ESD Protection A, B MIN TYP MAX ±60 UNITS V IEC 1000-4-2 Air-Gap Discharge ±2 IEC 1000-4-2 Contact Discharge ±8 Human Body Model ±15 kV SUPPLY CURRENT Normal Operation IQ No load, DI = VCC or GND, RE = GND, DE = VCC 10 mA Supply Current in Shutdown Mode ISHDN DE = GND, RE = VCC 10 µA Supply Current with Output Shorted with ±60V ISHRT DE = GND, RE = GND, output in three-state ±15 mA _______________________________________________________________________________________ 3 MAX3443E ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection SWITCHING CHARACTERISTICS (DRIVER) (VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Driver Propagation Delay tPLHA, tPLHB Figure 3, RL = 27Ω, CL = 50pF 60 ns Driver Differential Propagation Delay tDPLH, tDPHL Figure 4, RL = 54Ω, CL = 50pF 60 ns tLH, tHL Figure 4, RL = 54Ω, CL = 50pF 25 ns RL = 54Ω, CL = 50pF, tSKEWAB = |tPLHA - tPHLB|, tSKEWBA = |tPLHB - tPHLA| 10 ns RL = 54Ω, CL = 50pF, tDSKEW = |tDPLH - tDPHL| 10 ns Driver Differential Output Transition Time Driver Output Skew Differential Driver Output Skew tSKEWAB, tSKEWBA tDSKEW Maximum Data Rate fMAX Driver Enable Time to Output High tPDZH Figure 5, RL = 500Ω, CL = 50pF 1200 ns Driver Disable Time from Output High tPDHZ Figure 5, RL = 500Ω, CL = 50pF 1200 ns Driver Wake Time from Shutdown to Output High tPDHS Figure 5, RL = 500Ω, CL = 50pF 4.2 µs Driver Enable Time to Output Low tPDZL Figure 6, RL = 500Ω, CL = 50pF 1200 ns Driver Disable Time from Output Low tPDLZ Figure 6, RL = 500Ω, CL = 50pF 1200 ns Driver Wake Time from Shutdown to Output Low tPDLS Figure 6, RL = 500Ω, CL = 50pF 4.2 µs Time to Shutdown tSHDN RL = 500Ω, CL = 50pF 800 ns 4 10 _______________________________________________________________________________________ Mbps ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection (VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Receiver Propagation Delay tRPLH, tRPHL Figure 7, CL = 20pF, VID = 2V, VCM = 0 75 ns Receiver Output Skew tRSKEW CL = 20pF, tRSKEW = |tRPLH - tRPHL| 15 ns Receiver Enable Time to Output High tRPZH Figure 8, RL = 1kΩ, CL = 20pF 400 ns Receiver Disable Time from Output High tRPHZ Figure 8, RL = 1kΩ, CL = 20pF 400 ns Receiver Wake Time from Shutdown to Output High tRPSH Figure 8, RL = 1kΩ, CL= 20pF 4.2 µs Receiver Enable Time to Output Low tRPZL Figure 8, RL = 1kΩ, CL = 20pF 400 ns Receiver Disable Time from Output Low tRPLZ Figure 8, RL = 1kΩ, CL= 20pF 400 ns Receiver Wake Time from Shutdown to Output Low tRPSL Figure 8, RL = 1kΩ, CL= 20pF 4.2 µs 800 ns Time to Shutdown Note 2: ∆VOD and ∆VOC are the changes in VOD and VOC, respectively, when the DI input changes state. Note 3: The short-circuit output current applies to peak current just prior to foldback current limiting; the short-circuit foldback output current applies during current limiting to allow a recovery from bus contention. Typical Operating Characteristics (VCC = +5V, TA = +25°C, unless otherwise noted.) 4 DE = RE = GND 3 2 1 0.1 1 40 MAX3443E toc03 DE = GND, RE = VCC SUPPLY CURRENT (nA) SUPPLY CURRENT (mA) 5 10 RECEIVER OUTPUT CURRENT vs. OUTPUT LOW VOLTAGE RECEIVER OUTPUT CURRENT (mA) DE = VCC, RE = GND MAX3443E toc01 6 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX3443E toc02 NO-LOAD SUPPLY CURRENT vs. TEMPERATURE 35 30 25 20 15 10 5 0 0 0.01 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 TEMPERATURE (°C) TEMPERATURE (°C) OUTPUT LOW VOLTAGE (V) _______________________________________________________________________________________ 5 MAX3443E SWITCHING CHARACTERISTICS (RECEIVER) Typical Operating Characteristics (continued) (VCC = +5V, TA = +25°C, unless otherwise noted.) RECEIVER OUTPUT CURRENT vs. OUTPUT HIGH VOLTAGE 25 20 15 10 5 4.0 VOH, IOUT = +10mA 3.5 3.0 2.5 2.0 1.5 VOL, IOUT = -10mA 1.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 OUTPUT HIGH VOLTAGE (V) TEMPERATURE (°C) DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE 2.5 2.0 RL = 54Ω 1.5 1.0 30 20 0 0.5 1.5 1.0 MAX3443E toc08 1600 1200 0.5 RL = 54Ω 800 400 0 -400 -800 -1600 2.0 2.5 3.0 3.5 DIFFERENTIAL OUTPUT VOLTAGE (VA - VB) (V) -1200 0 6 40 2000 A, B CURRENT (µA) RL = 100Ω 50 A, B CURRENT vs. A, B VOLTAGE (TO GROUND) MAX3443E toc07 DIFFERENTIAL OUTPUT VOLTAGE (V) 3.0 60 0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 3.5 70 10 0.5 0 80 MAX3443E toc06 MAX3443E toc05 4.5 DRIVER OUTPUT CURRENT (mA) 30 5.0 RECEIVER OUTPUT VOLTAGE (V) 35 DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE RECEIVER OUTPUT VOLTAGE vs. TEMPERATURE MAX3443E toc04 40 RECEIVER OUTPUT CURRENT (mA) MAX3443E ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection DE = RE = GND -2000 -40 -25 -10 5 20 35 50 65 80 95 110 125 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 TEMPERATURE (°C) A, B VOLTAGE (V) _______________________________________________________________________________________ ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection RL 2 A DI VOD D B RL VCC VOC 2 Figure 1. Driver VOD and VCC A VID RO R B 0 VOL VOH IOL (+) IOH (-) Figure 2. Receiver VOH and VOL 3V VOM DI 1.5V 1.5V RL = 27Ω A DI tPLHA OUT D GENERATOR (NOTE 4) 0 S1 tPHLA VOH B 50Ω CL = 50pF (NOTE 5) VCC VOM = VOM A VOM VOL tPHLB VOH + VOL ≈ 1.5V 2 tPLHB VOH B VOM VOM VOL Figure 3. Driver Propagation Times 3V A DI D GENERATOR (NOTE 4) 0 RL = 54Ω B 1.5V 1.5V DI CL OUT tDPHL tDPLH ≈ 2.0V 50Ω 90% VCC CL (A–B) 50% 10% 90% 50% 10% CL = 50pF (NOTE 5) tLH ≈ -2.0V tHL Figure 4. Driver Differential Output Delay and Transition Times _______________________________________________________________________________________ 7 MAX3443E Test Circuits and Waveforms ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection MAX3443E Test Circuits and Waveforms (continued) A DI 0 OR 3V 3V S1 A, B D B DE GENERATOR (NOTE 4) DE RL = 500W CL = 50pF (NOTE 5) 1.5V 1.5V tPDZH 0 tPDHS tPDHZ 50W 0.25V A, B VOM = VOH + VOL 2 VOH VOM » 1.5V 0 Figure 5. Driver Enable and Disable Times VCC 3V A DI 0 OR 3V RL = 500Ω S1 A, B D 1.5V 1.5V tPDZL DE 0 tPDLS tPDLZ B DE GENERATOR (NOTE 4) CL = 50pF (NOTE 5) VCC A, B VOM 50Ω 0.25V VOL Figure 6. Driver Enable and Disable Times 3.0V A GENERATOR (NOTE 4) VID 50W R B RO (A–B) 1.5V 1.5V CL = 20pF (NOTE 5) 0 tRPLH tRPHL VCC 1.5V RO VOM VOM 0 Figure 7. Receiver Propagation Delay 8 _______________________________________________________________________________________ 0 ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection S1 S3 1.5V 1kW A -1.5V VID R RO VCC S2 B CL = 20pF (NOTE 5) GENERATOR (NOTE 4) 50W 3V RE 1.5V 0 3V S1 OPEN S2 CLOSED S3 = 1.5V RE 1.5V 0 tRPZH tRPSH tRPZL tRPSL VOH RO VCC RO 1.5V 1.5V 0 VOL 3V RE S1 CLOSED S2 OPEN S3 = -1.5V 1.5V 0 3V S1 OPEN S2 CLOSED S3 = 1.5V RE 1.5V 0 S1 CLOSED S2 OPEN S3 = -1.5V tRPHZ RO tRPLZ VOH 0.5V RO VCC 0.5V 0 VOL Figure 8. Receiver Enable and Disable Times Note 4: The input pulse is supplied by a generator with the following characteristics: f = 5MHz, 50% duty cycle; tr ≤ 6ns; Z0 = 50Ω. Note 5: CL includes probe and stray capacitance. Pin Description PIN NAME 1 RO Receiver Output. If RE = low and (A–B) ≥ -50mV, RO = high; if (A–B) ≤ -200mV, RO = low. FUNCTION 2 RE Receiver Output Enable. Pull RE low to enable RO. 3 DE Driver Output Enable. Force DE high to enable driver. Pull DE low to three-state the driver output. Drive RE high and pull DE low to enter low-power shutdown mode. 4 DI Driver Input. A logic low on DI forces the noninverting output low and the inverting output high. A logic high on DI forces the noninverting output high and the inverting output low. 5 GND 6 A Noninverting Receiver Input/Driver Output with Integrated ±15kV ESD Protection 7 B Inverting Receiver Input/Driver Output with Integrated ±15kV ESD Protection 8 VCC Ground Positive Supply, VCC = +4.75V to +5.25V _______________________________________________________________________________________ 9 MAX3443E Test Circuits and Waveforms (continued) MAX3443E ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection Function Tables MAX3443E (RS-485/RS-422) MAX3443E (RS-485/RS-422) RECEIVING TRANSMITTING INPUTS INPUTS OUTPUTS OUTPUT RE DE DI A B RE DE (A-B) RO 0 0 X High-Z High-Z 0 X ≥0.2V 1 0 1 0 0 1 0 X ≤-0.2V 0 0 1 1 1 0 0 X Open/Shorted 1 1 0 X Shutdown Shutdown 1 1 X High-Z 1 1 0 0 1 0 X Shutdown 1 1 1 1 0 1 X = Don’t care. X = Don’t care. Detailed Description Driver The driver accepts a single-ended, logic-level input (DI) and transfers it to a differential, RS-485/RS-422 level output (A and B). Driving DE high enables the driver, while pulling DE low places the driver outputs (A and B) into a high-impedance state (see the transmitting function table). Receiver The receiver accepts a differential, RS-485/RS-422 level input (A and B), and transfers it to a single-ended, logic-level output (RO). Pulling RE low enables the receiver, while driving RE high places the receiver inputs (A and B) into a high-impedance state (see the receiving function table). Low-Power Shutdown Force DE low and RE high to shut down the MAX3443E. A time delay of 50ns prevents the device from accidentally entering shutdown due to logic skews when switching between transmit and receive modes. Holding DE low and RE high for at least 800ns guarantees that the MAX3443E enters shutdown. In shutdown, the device consumes a maximum of 10µA supply current. ±60V Fault Protection The driver outputs/receiver inputs of RS-485 devices in industrial network applications often experience voltage faults resulting from shorts to the power bus that exceed the -7V to +12V range specified in the EIA/TIA485 standard. In these applications, ordinary RS-485 devices (typical absolute maximum -8V to +12.5V) require costly external protection devices. To reduce system complexity and eliminate this need for external protection, the driver outputs/receiver inputs of the MAX3443E withstand voltage faults up to ±60V with 10 respect to ground without damage. Protection is guaranteed regardless of whether the device is active, shut down, or without power. True Fail-Safe The MAX3443E uses a -50mV to -200mV differential input threshold to ensure true fail-safe receiver inputs. This threshold guarantees the receiver output is a logic high for shorted, open, or idle data lines. The -50mV to -200mV threshold complies with the ±200mV threshold specified in the EIA/TIA-485 standard. ±15kV ESD Protection As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against ESD encountered during handling and assembly. The MAX3443E receiver inputs/driver outputs (A, B) have extra protection against static electricity found in normal operation. Maxim’s engineers developed state-ofthe-art structures to protect these pins against ±15kV ESD without damage. After an ESD event, the MAX3443E continues working without latchup. ESD protection can be tested in several ways. The receiver inputs are characterized for protection to the following: • ±15kV using the Human Body Model • ±8kV using the Contact Discharge method specified in IEC 1000-4-2 (formerly IEC 801-2) • ±15kV using the Air-Gap Discharge method specified in IEC 1000-4-2 (formerly IEC 801-2) ESD Test Conditions ESD performance depends on a number of conditions. Contact Maxim for a reliability report that documents test setup, methodology, and results. ______________________________________________________________________________________ ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE Cs 100pF IP 100% 90% DISCHARGE RESISTANCE STORAGE CAPACITOR Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) AMPERES DEVICE UNDER TEST 36.8% 10% 0 0 TIME tRL tDL CURRENT WAVEFORM Figure 9a. Human Body ESD Test Model Figure 9b. Human Body Model Current Waveform Human Body Model Figure 9a shows the Human Body Model, and Figure 9b 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 device through a 1.5kΩ resistor. Body Model. Figure 10b shows the current waveform for the ±8kV IEC 1000-4-2 Level 4 ESD Contact Discharge test. The Air-Gap test involves approaching the device with a charge probe. The Contact Discharge method connects the probe to the device before the probe is energized. IEC 1000-4-2 Since January 1996, all equipment manufactured and/or sold in the European community has been required to meet the stringent IEC 1000-4-2 specification. The IEC 1000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The MAX3443E helps you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without additional ESD-protection components. The main difference between tests done using the Human Body Model and IEC 1000-4-2 is higher peak current in IEC 1000-4-2. Because series resistance is lower in the IEC 1000-4-2 ESD test model (Figure 10a), the ESD withstand voltage measured to this standard is generally lower than that measured using the Human CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE Cs 150pF Driver Output Protection Two mechanisms prevent excessive output current and power dissipation caused by faults, or bus contention. The first, a foldback current limit on the driver output stage, provides immediate protection against short circuits over the whole common-mode voltage range. The second, a thermal shutdown circuit, forces the driver I 100% 90% RD 330Ω DISCHARGE RESISTANCE STORAGE CAPACITOR IPEAK RC 50MΩ TO 100MΩ Machine Model The Machine Model for ESD testing uses a 200pF storage capacitor and zero-discharge resistance. It mimics the stress caused by handling during manufacturing and assembly. All pins (not just RS-485 inputs) require this protection during manufacturing. Therefore, the Machine Model is less relevant to the I/O ports than are the Human Body Model and IEC 1000-4-2. DEVICE UNDER TEST 10% tr = 0.7ns TO 1ns t 30ns 60ns Figure 10a. IEC 1000-4-2 ESD Test Model Figure 10b. IEC 1000-4-2 ESD Generator Current Waveform ______________________________________________________________________________________ 11 MAX3443E RD 1.5kW RC 1MW MAX3443E ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection outputs into a high-impedance state if the die temperature exceeds +160°C. Normal operation resumes when the die temperature cools to +140°C, resulting in a pulsed output during continuous short-circuit conditions. VCC 15µs Hot-Swap Capability Hot-Swap Inputs Inserting circuit boards into a hot, or powered, backplane may cause voltage transients on DE, RE, and receiver inputs A and B that can lead to data errors. For example, upon initial circuit board insertion, the processor undergoes a power-up sequence. During this period, the high-impedance state of the output drivers makes them unable to drive the MAX3443E enable inputs (DE, RE) to a defined logic level. Meanwhile, leakage currents up to 10µA from the high-impedance output, or capacitively coupled noise from VCC or GND, could cause an input to drift to an incorrect logic state. To prevent such a condition from occurring, the MAX3443E features hot-swap input circuitry on DE and RE to safeguard against unwanted driver activation during hot-swap situations. When VCC rises, an internal pulldown (or pullup for RE) circuit holds DE low for at least 10µs, and until the current into DE exceeds 200µA. After the initial power-up sequence, the pulldown circuit becomes transparent, resetting the hotswap tolerable input. Hot-Swap Input Circuitry At the driver enable input (DE), there are two NMOS devices, M1 and M2 (Figure 11). When VCC ramps from zero, an internal 15µs timer turns on M2 and sets the SR latch, which also turns on M1. Transistors M2, a 2mA current sink, and M1, a 100µA current sink, pull DE to GND through a 5.6kΩ resistor. M2 pulls DE to the disabled state against an external parasitic capacitance up to 100pF that may drive DE high. After 15µs, the timer deactivates M2 while M1 remains on, holding DE low against three-state leakage currents that may drive DE high. M1 remains on until an external current source overcomes the required input current. At this time, the SR latch resets M1 and turns off. When M1 turns off, DE reverts to a standard, high-impedance CMOS input. Whenever V CC drops below +1V, the input is reset. A complimentary circuit for RE utilizes two PMOS devices to pull RE to VCC. 12 TIMER TIMER DE (HOT SWAP) 5.6kΩ 100µA M1 2mA M2 Figure 11. Simplified Structure of the Driver Enable Pin (DE) Applications Information 128 Transceivers on the Bus The MAX3443E 1/4-unit-load receiver input impedance (48kΩ) allows up to 128 transceivers connected in parallel on one communication line. Connect any combination of these devices, and/or other RS-485 devices, for a maximum of 32 unit loads to the line. RS-485 Applications The MAX3443E transceiver provides bidirectional data communications on multipoint bus transmission lines. Figure 12 shows a typical network applications circuit. The RS-485 standard covers line lengths up to 4000ft. To minimize reflections, and reduce data errors, terminate the signal line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. J1708 Applications To configure the MAX3443E in a J1708 application, connect DI and RE to GND. Connect the signal to be transmitted to DE through an inverter. At each transceiver, terminate the bus with the load circuit (shown in Figure 13). When all transceivers are idle in this configuration, all receivers output a logic high because of the pullup resistor on A and pulldown resistor on B. Since RE is connected to GND, all transmitters on the bus listen at ______________________________________________________________________________________ ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection DI MAX3443E 120Ω 120Ω DE B B D D DI DE A RO B A B A A R R RO RE RE R R D D MAX3443E DI DE RO RE DI DE RO RE Figure 12. MAX3443E Typical RS-485 Network all times. Incoming data on DE enables the driver, which pulls the line low and causes all receivers to output a logic low. Chip Information TRANSISTOR COUNT: 310 PROCESS: BiCMOS VCC DE Tx R1 4.7kW DI B D R3 47W C1 2.2nF MAX3443E A Rx RO R J1708 BUS C2 2.2nF R4 47W R2 4.7kW RE Figure 13. J1708 Application Circuit ______________________________________________________________________________________ 13 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.) SOICN.EPS MAX3443E ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection 14 ______________________________________________________________________________________ ±60V Fault-Protected, 10Mbps, Fail-Safe RS-485 Transceiver with ±15kV ESD Protection PDIPN.EPS 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 ____________________ 15 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX3443E Package Information (continued) (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.)