19-5017; Rev 1; 4/10 High-ESD Profibus RS-485 Transceiver Features The MAX14770E is a half-duplex, Q35kV high ESDprotected transceiver for PROFIBUS-DP and RS-485 applications. In addition, it can be used for RS-422/V.11 communications. The MAX14770E is designed to meet IEC 61158-2, TIA/EIA-422-B, TIA/EIA-485-A, V.11, and X.27 standards. S Meets EIA 61158-2 Type 3 PROFIBUS-DP The MAX14770E operates from a +5V supply and has true fail-safe circuitry that guarantees a logic-high receiver output when the receiver inputs are open or shorted. S Thermal-Shutdown Protected The MAX14770E features a 1/4 standard-unit load receiver input impedance, allowing up to 128 1/4 unit load transceivers on the bus. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal-shutdown circuitry. The MAX14770E is available in 8-pin SO and tiny TDFN (3mm x 3mm) packages, and is specified over the extended (-40NC to +85NC) and automotive (-40NC to +125NC) temperature ranges. Applications PROFIBUS-DP Networks Industrial Fieldbuses Motion Controllers RS-485 Networks Machine Encoders S +4.5V to +5.5V Supply Voltage S 20Mbps Data Rate S Short-Circuit Protected S True Fail-Safe Receiver S Hot Swappable S High ESD Protection ±35kV Human Body Model (HBM) ±20kV IEC 61000-4-2 Air Gap ±10kV IEC 61000-4-2 Contact S -40NC to +125NC Automotive Temperature Range in Tiny 8-Pin (3mm x 3mm) TDFN Ordering Information PART TEMP RANGE PINPACKAGE MAX14770EESA+T -40NC to +85NC 8 SO MAX14770EATA+T -40NC to +125NC 8 TDFN-EP* TOP MARK — BMG +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. *EP = Exposed pad. Functional Diagram RO R RE A Typical PROFIBUS-DP Operating Circuit appears at end of data sheet. SHUTDOWN B DE DI D MAX14770E The PROFI BUS PROCESS FIELD BUS logo is a registered trademark of PROFIBUS and PROFINET International (PI). ________________________________________________________________ Maxim Integrated Products 1 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. MAX14770E General Description MAX14770E High-ESD Profibus RS-485 Transceiver ABSOLUTE MAXIMUM RATINGS (Voltages referenced to GND.) VCC. ......................................................................-0.3V to +6.0V RE, RO........................................................-0.3V to (VCC + 0.3V) DE, DI....................................................................-0.3V to +6.0V A, B......................................................................-8.0V to +13.0V Short-Circuit Duration (RO, A, B) to GND..................Continuous Continuous Power Dissipation (TA = +70NC) 8-Pin SOIC (derate 7.6mW/NC above +70NC).............606mW 8-Pin TDFN (derate 24.4mW/NC above +70NC).........1951mW Junction-to-Ambient Thermal Resistance (BJA) (Note 1) 8-Pin SO.....................................................................132NC/W 8-Pin TDFN...................................................................41NC/W Junction-to-Case Thermal Resistance (BJC) (Note 1) 8-Pin SO.......................................................................38NC/W 8-Pin TDFN.....................................................................8NC/W Operating Temperature Range 8-Pin SO.......................................................... -40NC to +85NC 8-Pin TDFN.................................................... -40NC to +125NC Storage Temperature Range............................. -65NC to +150NC Junction Temperature Range............................ -40NC to +150NC Lead Temperature (soldering, 10s).................................+300NC Soldering Temperature (reflow)......................................... 260NC Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, 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 = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2) PARAMETER SYMBOL Power-Supply Range VCC CONDITIONS Supply Current ICC DE = 1, RE = 0 or DE = 0, RE = 0 or DE = 1, RE = 1; no load Shutdown Supply Current ISH DE = 0, RE = 1 MIN TYP 4.5 2.5 MAX UNITS 5.5 V 4 mA 15 FA DRIVER Differential Driver Output |VOD| RL = 54I, DI = VCC or GND; Figure 1 2.1 Differential Driver Peak-to-Peak Output VODPP Figure 2 (Note 3) 4.0 Change in Magnitude of Differential Output Voltage DVOD RL = 54I; Figure 1 (Note 4) -0.2 Driver CommonMode Output Voltage VOC Change in CommonMode Voltage DVOC Driver Short-Circuit Output Current (Note 5) IOSD Driver Short-Circuit Foldback Output Current (Note 5) IOSDF RL = 54I; Figure 1 RL = 54I; Figure 1 (Note 4) V 6.8 V 0 +0.2 V 1.8 3 V +0.2 V -0.2 +250 0V P VOUT P +12V; output low -7V P VOUT P VCC; output high -250 (VCC - 1V) P VOUT P +12V; output low -15 -7V P VOUT P +1V; output high 2 _______________________________________________________________________________________ +15 mA mA High-ESD Profibus RS-485 Transceiver (VCC = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS LOGIC INPUTS Driver Input High Voltage VIH DE, DI, RE Driver Input Low Voltage VIL DE, DI, RE VHYS DE, DI, RE IIN DE, DI, RE Driver Input Hysteresis Driver Input Current Input Impedance in Hot Swap RDE 2.0 V 0.8 50 -1 Figure 11 until the first low-to-high transition of DE occurs RRE Figure 11 until the first high-to-low transition of RE occurs Input Current (A, B) IA, IB DE = GND, VCC = VGND or +5.5V Differential Input Capacitance CAB Between A and B, DE = RE = GND at 6MHz Receiver Differential Threshold Voltage VTH -7V P VCM P 12V 1 mV +1 5.6 V 10 FA kW RECEIVER Receiver Input Hysteresis VIN = 12V VIN = -7V +250 -200 8 -200 DVTH VCM = 0V Output High Voltage VOH IOUT = -1mA, VA - VB = VTH Output Low Voltage VOL IOUT = 1mA, VA - VB = -VTH Three-State Receiver Output Current IOZR 0V P VOUT P VCC -1 Receiver Input Resistance RIN -7V P VCM P 12V 48 Receiver Output Short-Circuit Current IOSR 0V P VRO P VCC -110 -125 FA pF -50 15 mV mV LOGIC OUTPUT VCC 1.5 V 0.4 V +1 FA kI +110 mA PROTECTION SPECIFICATIONS Thermal-Shutdown Threshold VTS +160 NC Thermal-Shutdown Hysteresis VTSH 15 NC ESD Protection, A and B Pins ESD Protection, All Other Pins HBM ±35 IEC 61000-4-2 Air-Gap Discharge to GND ±20 IEC 61000-4-2 Contact Discharge to GND ±10 HBM ±2 kV kV _______________________________________________________________________________________ 3 MAX14770E ELECTRICAL CHARACTERISTICS (continued) MAX14770E High-ESD Profibus RS-485 Transceiver ELECTRICAL CHARACTERISTICS (continued) (VCC = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 28 ns DRIVER SWITCHING CHARACTERISTICS Driver Propagation Delay tDPLH tDPHL RL = 54I, CL = 50pF; Figures 3 and 4 Differential Driver Output Skew |tDPLH - tDPHL| tDSKEW RL = 54I, CL = 50pF; Figures 3 and 4 1.2 ns Driver Output Transition Skew |tt(MLH)|, |tt(MHL)| tTSKEW RL = 54I, CL = 50pF; Figures 3 and 5 2 ns Driver Differential Output Rise or Fall Time tLH, tHL RL = 54I, CL = 50pF; Figures 3 and 4 Maximum Data Rate 15 20 ns Mbps Driver Enable to Output High tDZH RL = 500I, CL = 50pF; Figure 6 50 ns Driver Enable to Output Low tDZL RL = 500I, CL = 50pF; Figure 7 50 ns Driver Disable Time from Low tDLZ RL = 500I, CL = 50pF; Figure 7 40 ns Driver Disable Time from High tDHZ RL = 500I, CL = 50pF, Figure 6 40 ns Driver Enable Skew Time |tZL - tZH| RL = 500I, CL = 50pF; Figures 6 and 7 8 ns Driver Disable Skew Time |tLZ - tHZ| RL = 500I, CL = 50pF; Figures 6 and 7 8 ns Driver Enable from Shutdown to Output High tDZL(SHDN) RL = 500I, CL = 50pF; Figure 7 (Note 6) 100 Fs Driver Enable from Shutdown to Output Low tDZH(SHDN) RL = 500I, CL = 50pF; Figure 6 (Note 6) 100 Fs 800 ns CL = 15pF; Figures 8 and 9 (Note 7) 28 ns CL = 15pF; Figures 8 and 9 (Notes 7, 8) 2 ns Time to Shutdown tSHDN (Note 6) 50 RECEIVER SWITCHING CHARACTERISTICS Receiver Propagation Delay Receiver Output Skew tRPLH tRPHL tRSKEW 4 _______________________________________________________________________________________ High-ESD Profibus RS-485 Transceiver (VCC = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2) PARAMETER SYMBOL CONDITIONS Maximum Data Rate MIN TYP MAX 20 UNITS Mbps Receiver Enable to Output High tRZH S2 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns Receiver Enable to Output Low tRZL S1 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns Receiver Disable Time from Low tRLZ S1 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns Receiver Disable Time from High tRHZ S2 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns Receiver Enable from Shutdown to Output High tRZL(SHDN) S1 closed; RL = 1kI, CL = 15pF; Figure 10 (Notes 6, 7) 100 Fs Receiver Enable from Shutdown to Output Low tRZH(SHDN) S2 closed; RL = 1kI, CL = 15pF; Figure 10 (Notes 6, 7) 100 Fs 800 ns Time to Shutdown tSHDN (Note 6) 50 Devices are production tested at TA = +25NC. Specifications over temperature limits are guaranteed by design. VODPP is the difference in VOD, with the DI at high and DI at low. DVOD and DVOC are the changes in |VOD| and |VOC|, respectively, with the DI at high and DI at low. 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. Note 6: Shutdown is enabled by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 800ns, the device is guaranteed to have entered shutdown. Note 7: Capacitive load includes test probe and fixture capacitance. Note 8: Guaranteed by characterization, not production tested. Note Note Note Note 2: 3: 4: 5: _______________________________________________________________________________________ 5 MAX14770E ELECTRICAL CHARACTERISTICS (continued) MAX14770E High-ESD Profibus RS-485 Transceiver VCC A VCC DE RL 2 195I A DI VOD RL 2 110I VOD B VOC 195I B Figure 1. Driver DC Test Load Figure 2. VODPP Swing Under Profibus Equivalent Load Test VCC DE DI A VID B RL CL Figure 3. Driver Timing Test Circuit f = 1MHz, tLH P 3ns, tHL P 3ns VCC 1.5V DI 1.5V 0 1/2 VO tDPHL tDPLH B A 1/2 VO VO VDIFF = VA - VB VO VDIFF 80% 80% 0 -VO 20% 20% tLH tHL tDSKEW = |tDPLH - tDPHL| Figure 4. Driver Propagation Delays 6 _______________________________________________________________________________________ High-ESD Profibus RS-485 Transceiver MAX14770E 50% 50% A tt(MHL) tt(MLH) B 50% 50% Figure 5. Driver Transition Skew A 0 OR VCC DI D B S1 VCC OUT CL 50pF DE RL = 500I 1.5V tDZH, tDZH(SHDN) DE GENERATOR 0.25V 1.5V OUT 50I tDHZ 0 VOH 0 Figure 6. Driver Enable and Disable Times VCC 0 OR VCC DI D A RL = 500I S1 OUT B DE GENERATOR 50I VCC DE tDZL, tDZL(SHDN) 1.5V 0 tDLZ VCC OUT VOL 1.5V 0.25V Figure 7. Driver Enable and Disable Times _______________________________________________________________________________________ 7 MAX14770E High-ESD Profibus RS-485 Transceiver A ATE RECEIVER OUTPUT R VID B Figure 8. Receiver Propagation Delay Test Circuit t = 1MHz, tLH P 3ns, tHL P 3ns A 1V B -1V tRPHL VOH tRPLH VCC 2 RO VOL VCC 2 tRSKEW = |tRPHL - tRPLH| Figure 9. Receiver Propagation Delays +1.5V S3 -1.5V VID R RE GENERATOR RO R 1kI S1 VCC S2 CL 15pF 50I VCC 1.5V RE tRZH, tRZH (SHDN) 0 VCC S1 OPEN S2 CLOSED S3 = +1.5V 1.5V RE 0 S1 CLOSED S2 OPEN S3 = -1.5V tRZL, tRZL(SHDN) RO VOH VCC 2 0 VCC 1.5V RE 0 VCC 2 0.25V VOL RO VCC S1 OPEN S2 CLOSED S3 = +1.5V 1.5V 0 RE tRLZ tRHZ RO VCC VCC VOH 0 RO 0.25V VOL Figure 10. Receiver Enable and Disable Times 8 _______________________________________________________________________________________ S1 CLOSED S2 OPEN S3 = -1.5V High-ESD Profibus RS-485 Transceiver SUPPLY CURRENT vs. DATA RATE 1.0 0.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 1.0 0.5 0 5,000 0 10,000 15,000 -40 -25 -10 5 20 35 50 65 80 95 110 125 20,000 TEMPERATURE (°C) RECEIVER OUTPUT RO CURRENT vs. OUTPUT LOW VOLTAGE RECEIVER OUTPUT RO CURRENT vs. OUTPUT HIGH VOLTAGE RECEIVER PROPAGATION DELAY vs. TEMPERATURE 20 40 30 20 10 10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 MAX14770E toc06 25 RECEIVER PROPAGATION DELAY (ns) 50 OUTPUT CURRENT (mA) 30 MAX14770E toc05 60 MAX14770E toc04 40 20 15 10 5 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 5.0 OUTPUT HIGH VOLTAGE (V) TEMPERATURE (°C) DRIVER PROPAGATION DELAY vs. TEMPERATURE DIFFERENTIAL OUTPUT VOLTAGE VOD vs. OUTPUT CURRENT DIFFERENTIAL OUTPUT VOLTAGE VOD vs. TEMPERATURE 15 10 5 0 MAX14770E toc08 20 4.0 DIFFERENTIAL OUTPUT VOLTAGE (V) RL = 54Ω, CL = 50pF 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V) OUTPUT LOW VOLTAGE (V) MAX14770E toc07 0 1.5 DATA RATE (kbps) 50 OUTPUT CURRENT (mA) NO LOAD 15 10 2.0 TEMPERATURE (°C) 60 DRIVER PROPAGATION DELAY (ns) 30 25 20 5 0 0 25 PROFIBUS EQUIVALENT LOAD 40 35 2.5 2.8 RL = 54Ω 2.7 2.6 MAX14770E toc09 DE = GND 45 3.0 MAX14770E toc03 55 50 SUPPLY CURRENT (mA) 2.0 MAX14770E toc02 DE = VCC 1.5 60 MAX14770E toc01 NO-LOAD SUPPLY CURRENT (mA) 2.5 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT (µA) NO-LOAD DC SUPPLY CURRENT vs. TEMPERATURE 2.5 2.4 2.3 2.2 2.1 2.0 0 20 40 60 OUTPUT CURRENT (mA) 80 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) _______________________________________________________________________________________ 9 MAX14770E Typical Operating Characteristics (VCC = +5V, TA = +25NC, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = +5V, TA = +25NC, unless otherwise noted.) 100 80 60 40 20 100 80 60 40 5 0 3 6 9 12 4 3 2 0 -7 -5 -3 -1 1 3 -40 -25 -10 5 20 35 50 65 80 95 110 125 5 OUTPUT HIGH VOLTAGE (V) TEMPERATURE (°C) DRIVER OUTPUT TRANSITION SKEW vs. TEMPERATURE DRIVER OUTPUT RISE AND FALL TIME vs. TEMPERATURE DRIVER ENABLE TO OUTPUT HIGH tDZH RL = 54Ω, CL = 50pF 16 4 2 FALL TIME 12 TIME (ns) 3 14 RL = 54Ω, CL = 50pF 10 MAX14770E toc14 OUTPUT LOW VOLTAGE (V) MAX14770E toc13 0 RL = 54Ω, CL = 50pF 1 20 0 5 MAX14770E toc11 120 OUTPUT CURRENT (mA) 120 OUTPUT CURRENT (mA) 140 MAX14770E toc10 140 DRIVER DIFFERENTIAL SKEW tDSKEW vs. TEMPERATURE MAX14770E toc12 DRIVER OUTPUT CURRENT vs. OUTPUT HIGH VOLTAGE DRIVER OUTPUT SKEW (ns) DRIVER OUTPUT CURRENT vs. OUTPUT LOW VOLTAGE DRIVER OUTPUT TRANSITION SKEW (ns) MAX14770E High-ESD Profibus RS-485 Transceiver MAX14770E toc15 DI = VCC, RL = 500Ω, CL = 50pF DE 2V/div RISE TIME 8 6 4 1 2 0 A 2V/div 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TEMPERATURE (°C) DRIVER ENABLE TO OUTPUT LOW tDZL DRIVER DISABLE TIME FROM LOW tDLZ MAX14770E toc16 DRIVER DISABLE TIME FROM HIGH tDHZ MAX14770E toc17 DI = VCC, RL = 500Ω, CL = 50pF 10ns/div 10ns/div MAX14770E toc18 DI = VCC, RL = 500Ω, CL = 50pF DI = VCC, RL = 500Ω, CL = 50pF DE 2V/div DE 2V/div B 2V/div B 2V/div 10ns/div DE 2V/div A 2V/div 10ns/div 10 ������������������������������������������������������������������������������������� High-ESD Profibus RS-485 Transceiver TOP VIEW + RO 1 RE 2 MAX14770E DE 3 DI + 4 8 VCC RO 1 7 B RE 2 A DE 3 5 GND DI 4 6 SO MAX14770E *EP 8 VCC 7 B 6 A 5 GND TDFN (3mm × 3mm) *CONNECT EXPOSED PAD TO GND. Pin Description PIN NAME FUNCTION 1 RO Receiver Output. When RE is low and (A - B) R -50mV, RO is high; if (A - B) P -200mV, RO is low. 2 RE Receiver Enable. Drive RE low to enable RO; RO is high impedance when RE is high. Drive RE high and DE low to enter low-power shutdown mode. 3 DE Driver Enable. Drive DE high to enable driver output. The driver outputs are high impedance when DE is low. Drive RE high and DE low to enter low-power shutdown mode. 4 DI Driver Input. With DE high, a low on DI forces the noninverting output, A, low and the inverting output, B, high. Similarly, a high on DI forces the noninverting output, A, high and the inverting output, B, low. 5 GND 6 A Noninverting Receiver Input and Noninverting Driver Output 7 B Inverting Receiver Input and Inverting Driver Output 8 VCC — EP Ground Positive Supply. Bypass VCC to GND with a 0.1FF ceramic capacitor as close as possible to the device. Exposed Pad (TDFN Only). Connect EP to GND. ______________________________________________________________________________________ 11 MAX14770E Pin Configurations MAX14770E High-ESD Profibus RS-485 Transceiver Detailed Description The MAX14770E is a half-duplex, Q35kV high ESDprotected transceiver for PROFIBUS-DP, RS-485, and RS-422 communications. The device features true failsafe circuitry that guarantees a logic-high receiver output when the receiver inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers disabled (see the True Fail-Safe section). The MAX14770E supports data rates up to 20Mbps. The MAX14770E operates from a single +4.5V to +5.5V supply. Drivers are output short-circuit current limited. Thermal-shutdown circuitry protects drivers against excessive power dissipation. When activated, the thermal-shutdown circuitry places the driver outputs into a high-impedance state. The MAX14770E has a hotswap input structure that prevents disturbances on the differential signal lines when the MAX14770E is powered up (see the Hot-Swap Capability section). True Fail-Safe The MAX14770E guarantees 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 having the receiver Table 1. Functional Table (Transmitting) TRANSMITTING INPUTS OUTPUTS RE X DE DI B A 1 1 0 1 X 1 0 1 0 0 0 X High-Z High-Z 1 0 X High-Z and shutdown X = Don’t care. Table 2. Functional Table (Receiving) RECEIVING INPUTS OUTPUT RE 0 DE A-B RO X R -0.05V 1 0 X P -0.2V 0 0 X Open/shorted 1 1 1 X High-Z 1 0 X High-Z and shutdown X = Don’t care. 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 0V by the termination. With the receiver thresholds of the MAX14770E, this results in a logic-high with a 50mV minimum noise margin. The -50mV to -200mV threshold complies with the Q200mV EIA/TIA-485 standard. Hot-Swap Capability Hot-Swap Inputs When circuit boards are inserted into a hot or powered backplane, disturbances to the enable inputs and differential receiver inputs can lead to data errors. Upon initial circuit board insertion, the processor undergoes its power-up sequence. During this period, the processor output drivers are high impedance and are unable to drive the DE and RE inputs of the MAX14770E to a defined logic level. Leakage currents up to 10FA from the highimpedance output of a controller could cause DE and RE to drift to an incorrect logic state. Additionally, parasitic circuit board capacitance could cause coupling of VCC or GND to DE and RE. These factors could improperly enable the driver or receiver. However, the MAX14770E has hot-swap inputs that avoid these potential problems. When VCC rises, an internal pulldown circuit holds DE low and RE high. After the initial power-up sequence, the pulldown circuit becomes transparent, resetting the hot-swap-tolerable inputs. Hot-Swap Input Circuitry The MAX14770E DE and RE enable inputs feature hot-swap capability. At the input, there are two NMOS devices, M1 and M2 (Figure 11). When VCC ramps from 0, an internal 15Fs timer turns on M2 and sets the SR latch that also turns on M1. Transistors M2, a 1mA current sink, and M1, a 100FA current sink, pull DE to GND through a 5.6kI resistor. M2 is designed to pull DE to the disabled state against an external parasitic capacitance up to 100pF that can drive DE high. After 15Fs, the timer deactivates M2 while M1 remains on, holding DE low against three-state leakages that can drive DE high. M1 remains on until an external source overcomes the required input current. At this time, the SR latch resets and M1 turns off. When M1 turns off, DE reverts to a standard, high-impedance CMOS input. Whenever VCC drops below 1V, the hot-swap input is reset. For RE, there is a complementary circuit employing two PMOS devices pulling RE to VCC. 12 ������������������������������������������������������������������������������������� High-ESD Profibus RS-485 Transceiver Applications Information 128 Transceivers on the Bus The standard RS-485 receiver input impedance is one unit load, and a standard driver can drive up to 32 unit loads. The MAX14770E transceiver has a 1/4 unit load receiver, which 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. Low-Power Shutdown Mode Low-power shutdown mode is initiated by bringing both RE high and DE low. In shutdown, the devices draw only 15FA (max) of supply current. RE and DE can be driven simultaneously; the devices 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 800ns, the devices are guaranteed to enter shutdown. Driver Output Protection Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. The first, a foldback current limit on the output stage, provides immediate protection against short circuits over the whole common-mode voltage range (see the Typical Operating Characteristics). The second, a thermal-shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature exceeds +160NC (typ). Typical Application The MAX14770E transceivers are designed for bidirectional data communications on multipoint bus transmission lines. Figure 12 shows a typical network applications circuit. To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible. Profibus Termination The MAX14770E is designed for driving PROFIBUS-DP termination networks. With a worst-case loading of two termination networks with 220I termination impedance and 390I pullups/pulldowns, the drivers can drive V(A - B) > 2.1V output. VCC 15Fs TIMER TIMER DE DRIVER ENABLE (HOT SWAP) 5.6kI 100FA M1 1mA M2 Figure 11. Simplified Structure of the Driver Enable Pin (DE) ______________________________________________________________________________________ 13 MAX14770E Thermal-Shutdown Protection The MAX14770E features thermal-shutdown circuitry. The internal switch turns off when the junction temperature exceeds +160NC (typ) and immediately goes into a fault mode. The device exits thermal shutdown after the junction temperature cools by 15NC (typ). MAX14770E High-ESD Profibus RS-485 Transceiver 120I DI 120I DE B B D D A DE B RO A B DI A A R R RE RO RE MAX14770E R D DI DE RO RE R D DI DE RO RE Figure 12. Typical Half-Duplex RS-485 Network RC 1MI CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE CS 100pF RD 1.5kI 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 Figure 13. Human Body ESD Test Model Extended ESD Protection ESD protection structures are incorporated on all pins to protect against electrostatic discharges up to Q2kV (HBM) encountered during handling and assembly. A and B are further protected against high ESD up to Q35kV (HBM) without damage. The A and B pins are also protected against Q20kV Air-Gap and Q10kV Contact IEC61000-4-2 ESD events. The ESD structures withstand high ESD both in normal operation and when the device is powered down. After an ESD event, the MAX14770E continues to function without latchup. 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. tRL TIME tDL CURRENT WAVEFORM Figure 14. Human Body Current Waveform Human Body Model Figure 13 shows the HBM. Figure 14 shows the current waveform it generates when discharged into a lowimpedance state. This model consists of a 100pF capacitor charged to the ESD voltage of interest that is then discharged into the device through a 1.5kI resistor. IEC 61000-4-2 The IEC 61000-4-2 standard covers ESD testing and performance of finished equipment. It does not specifically refer to integrated circuits. The MAX14770E is specified for Q20kV Air-Gap Discharge and Q10kV Contact Discharge IEC 61000-4-2 on the A and B pins. The main difference between tests done using the HBM and IEC 61000-4-2 is higher peak current in IEC 61000-4-2. Because series resistance is lower in the IEC 61000-4-2 14 ������������������������������������������������������������������������������������� High-ESD Profibus RS-485 Transceiver RD 330I CS 150pF IPEAK HIGHVOLTAGE DC SOURCE 100% 90% DISCHARGE RESISTANCE CHARGE-CURRENTLIMIT RESISTOR MAX14770E RC 50MI TO 100MI DEVICE UNDER TEST STORAGE CAPACITOR 10% t tR = 0.7ns TO 1ns 30ns 60ns Figure 15. IEC61000-4-2 ESD Test Model Figure 16. IEC61000-4-2 ESD Generator Current Waveform Typical PROFIBUS-DP Operating Circuit VCC RO 0.1FF R VCC 0.1FF 390I DI D 390I RE A 220I 220I SHUTDOWN SHUTDOWN B DE DI DE A D B 390I RE RO R 390I MAX14770E MAX14770E GND GND ESD test model (Figure 15), the ESD-withstand voltage measured to this standard is generally lower than that measured using the HBM. Figure 16 shows the current waveform for the Q10kV IEC 61000-4-2 Level 4 ESD Contact Discharge test. The Air-Gap Discharge test involves approaching the device with a charged probe. The Contact Discharge method connects the probe to the device before the probe is energized. Chip Information 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 PACKAGE CODE DOCUMENT NO. 8 SO S8+4 21-0041 8 TDFN-EP T833+2 21-0137 PROCESS: BiCMOS ______________________________________________________________________________________ 15 MAX14770E High-ESD Profibus RS-485 Transceiver Revision History REVISION NUMBER REVISION DATE 0 10/09 Initial release — 1 4/10 Switched the position of the pins DE and DI (TDFN) in the Pin Configurations. 11 DESCRIPTION PAGES CHANGED 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 © 2010 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.