19-5131; Rev 0; 2/10 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers The MAX14840E/MAX14841E are +3.3V ESD-protected transceivers intended for half-duplex RS-485 communication up to 40Mbps. These transceivers are optimized for high speeds over extended cable runs while maximizing tolerance to noise. The MAX14840E features symmetrical fail-safe and larger receiver hysteresis, providing improved noise rejection and improved recovered signals in high-speed and long cable applications. The MAX14841E has true failsafe receiver inputs guaranteeing a logic-high receiver output when inputs are shorted or open. The MAX14840E/MAX14841E transceivers draw 1.5mA (typ) supply current when unloaded or when fully loaded with the drivers disabled. Hot-swap capability eliminates undesired transitions on the bus during power-up or hot insertion. The MAX14840E/MAX14841E are available in 8-pin SO and small, 8-pin (3mm x 3mm) TDFN-EP packages. Both devices operate over the -40NC to +125NC automotive temperature range. Applications Motion Controllers Fieldbus Networks Features S Half-Duplex RS-485 Transceivers S +3.3V Supply Voltage S 40Mbps Maximum Data Rate S Large (170mV) Receiver Hysteresis on MAX14840E S Symmetrical Fail-Safe Receiver Input on MAX14840E S Fail-Safe Receiver Input (MAX14841E) S Hot-Swap Capability S Short-Circuit Protected Outputs S Thermal Self-Protection S Low 10A (max) Shutdown Current S Extended ESD Protection for RS-485 I/O Pins 35kV Human Body Model (HBM) 20kV Air-Gap Discharge per IEC 61000-4-2 12kV Contact Discharge per IEC 61000-4-2 S Automotive -40C to +125C Operating Temperature Range S Available in Industry-Standard 8-Pin SO or Space-Saving, 8-Pin TDFN-EP (3mm x 3mm) Packages Industrial Control Systems Backplane Buses HVAC Networks Ordering Information/Selector Guide PART FAIL SAFE TEMP RANGE MAX14840EASA+ Symmetrical -40NC to +125NC PIN-PACKAGE 8 SO MAX14840EATA+ Symmetrical -40NC to +125NC 8 TDFN-EP* MAX14841EASA+ True -40NC to +125NC 8 SO MAX14841EATA+ True -40NC to +125NC 8 TDFN-EP* +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. ________________________________________________________________ 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. MAX14840E/MAX14841E General Description MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers 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 SO (derate 7.6mW/NC above +70NC) ................ 606mW 8-Pin TDFN (derate 24.4mW/NC above +70NC) . ...... 1951mW Junction-to-Case Thermal Resistance (BJC) (Note 1) 8-Pin SO........................................................................38NC/W 8-Pin TDFN . ...................................................................8NC/W Junction-to-Ambient Thermal Resistance (BJA) (Note 1) 8-Pin SO . ...................................................................132NC/W 8-Pin TDFN . .................................................................41NC/W Operating Temperature Range . ..................... -40NC to +125NC Junction Temperature ................................................... +150NC Storage Temperature Range .......................... -65NC 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.com/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. DC ELECTRICAL CHARACTERISTICS (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.) (Notes 2, 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 3.6 V 4 mA 10 FA POWER SUPPLY Supply Voltage VCC 3.0 Supply Current ICC DE = RE = VCC, or DE = RE = GND, or DE = VCC, RE = GND, DI = VCC or GND, no load Shutdown Supply Current ISH DE = GND and RE = VCC VOD RL = 54I, Figure 1 1.5 RL = 54I, Figure 1 (Note 4) -0.2 1.5 DRIVER Differential Driver Output Change in Magnitude of Differential Output Voltage Driver Common-Mode Output Voltage Change in Common-Mode Voltage DVOD VOC DVOC RL = 54I, Figure 1 RL = 54I, Figure 1 (Note 4) -0.2 2.2 Single-Ended Driver Output High VOH A/B output, IOUT = -20mA Single-Ended Driver Output Low VOL A/B output, IOUT = 20mA 0V P VOUT P +12V, output low Driver Short-Circuit Output Current |IOSD| -7V P VOUT P VCC, output high V 0 +0.2 V VCC/2 3 V 0.2 V V 0.8 250 250 V mA RECEIVER VIN = +12V Input Current (A and B) IA,B DE = GND, VCC = GND or +3.6V Differential Input Capacitance CA,B Between A and B, DE = GND, f = 2MHz VIN = -7V 1000 -800 12 2 _______________________________________________________________________________________ FA pF 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.) (Notes 2, 3) PARAMETER Receiver Differential Threshold Voltage (MAX14840E Only) SYMBOL CONDITIONS MIN MAX UNITS VTHF -7V P VCM P 12V, VOD falling -200 -10 mV VTHR -7V P VCM P 12V, VOD rising 10 200 mV VCM = 0V 20 170 -200 -105 Receiver Input Hysteresis (MAX14840E Only) Receiver Differential Threshold Voltage (MAX14841E Only) Receiver Input Hysteresis (MAX14841E Only) VTH DVTH -7V P VCM P 12V VCM = 0V TYP mV -10 10 mV mV LOGIC INTERFACE DE, DI 2.0 RE 2.0 5.5 Input High Voltage VIH Input Low Voltage VIL DE, DI, RE VHYS DE, DI, RE IIN DE, DI, RE -1 +1 FA DE, RE 1 10 kI Input Hysteresis Input Current Input Impedance on First Transition 0.8 50 Output High Voltage VOH RE = GND, IO = -1mA, VA - VB > 200mV Output Low Voltage VOL RE = GND, IO = 1mA, VA - VB < -200mV Three-State Output Current at Receiver IOZR RE = VCC, 0V P VO P VCC Receiver Output Short-Circuit Current IOSR 0V P VRO P VCC V V mV VCC 1.5 V 0.4 V -1 +1 FA -95 +95 mA PROTECTION Thermal Shutdown Threshold TTS 160 NC Thermal Shutdown Hysteresis TTSH 15 NC ESD Protection: A, B to GND ESD Protection: All Other Pins IEC 61000-4-2 Air Gap Discharge Q20 IEC 61000-4-2 Contact Discharge Q12 HBM Q35 HBM Q2 kV kV SWITCHING CHARACTERISTICS (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.) (Notes 2, 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 5 12 20 5 12 20 UNITS DRIVER tDPLH Propagation Delay tDPHL RL = 54I, CL = 50pF, Figures 2 and 3 (Note 5) ns Differential Driver Output Skew |tDPLH - tDPHL| tDSKEW RL = 54I, CL = 50pF, Figures 2 and 3 (Notes 5, 8) 2 ns Driver Differential Output Rise or Fall Time tHL, tLH RL = 54I, CL = 50pF, Figures 2 and 3 (Notes 5, 8) 7.5 ns _______________________________________________________________________________________ 3 MAX14840E/MAX14841E DC ELECTRICAL CHARACTERISTICS (continued) MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers SWITCHING CHARACTERISTICS (continued) (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.) (Notes 2, 3) PARAMETER Maximum Data Rate SYMBOL CONDITIONS DRMAX MIN TYP MAX 40 UNITS Mbps Driver Enable to Output High tDZH RL = 110I, CL = 50pF, Figures 4 and 5 (Notes 5, 6) 30 ns Driver Enable to Output Low tDZL RL = 110I, CL = 50pF, Figures 4 and 5 (Notes 5, 6) 30 ns Driver Disable Time from Low tDLZ RL = 110I, CL = 50pF, Figures 4 and 5 (Notes 5, 6) 30 ns Driver Disable Time from High tDHZ RL = 110I, CL = 50pF, Figures 4 and 5 (Notes 5, 6) 30 ns Driver Enable from Shutdown to Output Low tDZL(SHDN) RL = 110I, CL = 50pF, Figures 4 and 5 (Notes 5, 6) 4 Fs Driver Enable from Shutdown to Output High tDZH(SHDN) RL = 110I, CL = 50pF, Figures 4 and 5 (Notes 5, 6) 4 Fs 800 ns Time to Shutdown tSHDN (Note 7) 50 RECEIVER Propagation Delay tRPLH tRPHL Receiver Output Skew tRSKEW Maximum Data Rate DRMAX 25 CL = 15pF, Figures 6 and 7 (Note 5) 25 CL = 15pF, Figures 6 and 7 (Notes 5, 8) 2 40 ns ns Mbps Receiver Enable to Output High tRZH RL = 1kI, CL = 15pF, Figure 8 (Notes 5, 6) 20 ns Receiver Enable to Output Low tRZL RL = 1kI, CL = 15pF, Figure 8 (Notes 5, 6) 20 ns Receiver Disable Time from Low tRLZ RL = 1kI, CL = 15pF, Figure 8 (Notes 5, 6) 20 ns Receiver Disable Time from High tRHZ RL = 1kI, CL = 15pF, Figure 8 (Notes 5, 6) 20 ns Receiver Enable from Shutdown to Output Low tRZL(SHDN) RL = 1kI, CL = 15pF, Figure 8 (Notes 5, 6) 4 Fs Receiver Enable from Shutdown to Output High tRZH(SHDN) RL = 1kI, CL = 15pF, Figure 8 (Notes 5, 6) 4 Fs 800 ns Time to Shutdown tSHDN (Note 7) 50 Note 2: All devices are 100% production tested at TA = +25NC. Specifications for all temperature limits are guaranteed by design. Note 3: 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 4: DVOD and DVOC are the changes in VOD and VOC, respectively, when the DI input changes state. Note 5: Capacitive load includes test probe and fixture capacitance. Note 6: The timing parameter refers to the driver or receiver enable delay when the device has exited the initial hot-swap protect state and is in normal operating mode. Note 7: Shutdown is enabled by driving RE high and DE low. The device is guaranteed to have entered shutdown after tSHDN has elapsed. Note 8: Parameter is guaranteed by characterization and not production tested. 4 _______________________________________________________________________________________ 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers A VCC DE RL 2 A DI VOD B VOD RL 2 RL CL VOC B Figure 1. Driver DC Test Load Figure 2. Driver Timing Test Circuit f = 1MHz, tLH = 3ns, tHL = 3ns VCC 1.5V 1.5V 0 tDPHL tDPLH B A VOD VOD = [VA - VB] VO VOD 90% 90% 0 10% -VO 10% tLH tHL tDSKEW = tDPLH - tDPHL Figure 3. Driver Propagation Delays A GND OR VCC DI D B S1 VCC OUT CL 50pF RL = 110I DE 1.5V tDZH, tDZH(SHDN) DE GENERATOR 50I 0.25V OUT 1.5V tDHZ 0 VOH 0 Figure 4. Driver Enable and Disable Times (tDZH, tDHZ) _______________________________________________________________________________________ 5 MAX14840E/MAX14841E Test and Timing Diagrams 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers MAX14840E/MAX14841E Test and Timing Diagrams (continued) VCC 0 OR VCC A DI RL = 110I S1 OUT D B DE GENERATOR 50I VCC DE tDZL, tDZL(SHDN) 1.5V 0 tDLZ VCC OUT 1.5V VOL 0.25V Figure 5. Driver Enable and Disable Times (tDLZ, tDZL) A ATE R VID RECEIVER OUTPUT B Figure 6. Receiver Propagation Delay Test Circuit f = 1MHz, tLH P 3ns, tHL P 3ns A 1V B VOH RO VOL -1V tRPHL tRPLH VCC 2 VCC 2 tRSKEW = tRPHL - tRPLH Figure 7. Receiver Propagation Delays 6 _______________________________________________________________________________________ 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers +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 VOL RO VCC S1 OPEN S2 CLOSED S3 = +1.5V 1.5V tRLZ VCC VOH 0.25V S1 CLOSED S2 OPEN S3 = -1.5V 0 RE tRHZ RO VCC 0 RO 0.25V VOL Figure 8. Receiver Enable and Disable Times _______________________________________________________________________________________ 7 MAX14840E/MAX14841E Test and Timing Diagrams (continued) Typical Operating Characteristics (VCC = +3.3V, TA = +25NC, unless otherwise noted.) NO-LOAD SUPPLY CURRENT vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE 2 1 2 1 RE = GND AND DE = VCC, OR RE = VCC AND DE = VCC -15 10 35 60 85 110 125 -40 -15 10 35 60 85 54I LOAD 60 NO LOAD 40 20 0 0 110 125 0 10 20 40 30 TEMPERATURE (C) TEMPERATURE (C) DATA RATE (Mbps) RECEIVER OUTPUT HIGH VOLTAGE vs. OUTPUT CURRENT RECEIVER OUTPUT LOW VOLTAGE vs. OUTPUT CURRENT DIFFERENTIAL DRIVER OUTPUT VOLTAGE vs. OUTPUT CURRENT VRO (V) 3 4 3 4 VOD (V) 4 5 3 2 2 2 1 1 1 0 0 0 0 5 10 15 25 20 MAX14840E toc06 5 MAX14840E toc04 5 MAX14840E toc05 -40 0 3 6 9 12 15 18 21 24 0 27 20 40 60 80 IRO (mA) IRO (mA) IOD (mA) DIFFERENTIAL DRIVER OUTPUT VOLTAGE vs. TEMPERATURE DRIVER OUTPUT CURRENT vs. OUTPUT HIGH VOLTAGE DRIVER OUTPUT CURRENT vs. OUTPUT LOW VOLTAGE 2 1 60 40 20 0 -40 -15 10 35 60 TEMPERATURE (C) 85 110 125 100 80 60 40 20 RL = 54I 0 120 OUTPUT CURRENT (mA) 80 OUTPUT CURRENT (mA) 3 140 MAX14840E toc09 100 MAX14840E toc07 4 MAX14840E toc08 VRO (V) 80 RE = VCC DE = GND 0 MAX14840E toc03 3 SUPPLY CURRENT (mA) 3 SUPPLY CURRENT vs. DATA RATE 100 MAX14840E toc02 MAX14840E toc01 4 SUPPLY CURRENT (A) SUPPLY CURRENT (mA) 4 DIFFERENTIAL DRIVER OUTPUT VOLTAGE (V) MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers -7 -5 -3 -1 1 OUTPUT HIGH VOLTAGE (V) 3 5 0 0 2 4 6 8 OUTPUT LOW VOLTAGE (V) 8 _______________________________________________________________________________________ 10 12 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers DIFFERENTIAL DRIVER SKEW (tDSKEW) vs. TEMPERATURE RL = 54I, CL = 50pF 15 tDPHL 10 5 1.5 RL = 54I, CL = 50pF 8 TIME (ns) DRIVER OUTPUT SKEW (ns) tDPLH 10 MAX14840E toc11 2.0 MAX14840E toc10 20 1.0 0.5 6 RISE TIME 4 FALL TIME 2 RL = 54I, CL = 50pF 0 0 0 10 35 60 85 110 125 -40 -15 TEMPERATURE (C) 10 35 60 85 -40 110 125 -15 DRIVER OUTPUT TRANSITION SKEW (tDSKEW) vs. TEMPERATURE 3 60 85 110 125 RECEIVER PROPAGATION DELAY vs. TEMPERATURE 25 RECEIVER PROPAGATION DELAY (ns) RL = 54I, CL = 50pF 35 2 1 MAX14840E toc14 4 10 TEMPERATURE (C) TEMPERATURE (C) 20 15 tRPLH 10 tRPHL 5 CL = 50pF 0 0 -40 -15 10 35 60 85 -40 110 125 DRIVER/RECEIVER PROPAGATION DELAY 10 35 60 85 110 125 RECEIVER INPUT CAPACITANCE vs. FREQUENCY MAX14840E toc15 A/B 2V/div RO 5V/div MAX14840E toc16 70 60 DI 5V/div 10ns/div -15 TEMPERATURE (C) TEMPERATURE (C) CAPACITANCE (pF) -15 MAX14840E toc13 -40 DRIVER OUTPUT TRANSITION SKEW (ns) DRIVER PROPAGATION DELAY (ns) 25 DRIVER OUTPUT RISE AND FALL TIME vs. TEMPERATURE MAX14840E toc12 DRIVER PROPAGATION DELAY vs. TEMPERATURE 50 40 30 20 10 0 100 1000 10,000 100,000 FREQUENCY (kHz) _______________________________________________________________________________________ 9 MAX14840E/MAX14841E Typical Operating Characteristics (continued) (VCC = +3.3V, TA = +25NC, unless otherwise noted.) 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers MAX14840E/MAX14841E Pin Configurations TOP VIEW VCC B A GND 8 7 6 5 MAX14840E MAX14841E *EP + 1 2 3 4 RO RE DE DI RO 1 RE 2 DE 3 DI 4 MAX14840E MAX14841E 8 VCC 7 B 6 A 5 GND SO TDFN *CONNECT EXPOSED PAD (EP) TO GND. Pin Descriptions PIN NAME FUNCTION 1 RO Receiver Output. See the Function Table. 2 RE Active-Low Receiver-Output 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. RE is a hot-swap input (see the Hot-Swap Capability section for details). 3 DE Driver-Output Enable. Drive DE high to enable driver outputs. These outputs are high impedance when DE is low. Drive RE high and DE low to enter low-power shutdown mode. DE is a hot-swap input (see the Hot-Swap Capability section for details). 4 DI Driver Input. With DE high, a low on DI forces the A output low and the B output high. Similarly, a high on DI forces the A output high and the B output 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 Voltage Input. Bypass VCC with a 0.1FF ceramic capacitor to GND. Exposed Pad (TDFN Only). Connect EP to GND. 10 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers TRANSMITTING INPUTS OUTPUTS RE X DE DI B A 1 1 0 1 X 1 0 1 0 0 0 X High Impedance High Impedance 1 0 X Shutdown (see note) RECEIVING (MAX14840E) INPUTS OUTPUTS RE 0 DE A-B RO X R 200mV 1 0 X P -200mV 0 0 X Open/Shorted Previous State 1 1 X High Impedance 1 0 X Shutdown (see note) RECEIVING (MAX14841E) INPUTS OUTPUTS RE 0 DE A-B RO X R -10mV 1 0 X P -200mV 0 0 X Open/Shorted 1 1 1 X High Impedance 1 0 X Shutdown (see note) X = Don't care. Note: Shutdown mode, driver, and receiver outputs are in high impedance. Functional Diagram VCC MAX14840E MAX14841E R RO B RE SHUTDOWN DE DI A D GND ______________________________________________________________________________________ 11 MAX14840E/MAX14841E Function Table MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers Detailed Description normal conditions, where UART signaling is used, this means that the state on the line prior to all drivers being disabled is a logic-high (i.e., a UART STOP bit). The MAX14840E/MAX14841E are +3.3V ESD-protected RS-485 transceivers intended for high-speed, half-duplex communications. A hot-swap capability eliminates false transitions on the bus during power-up or hot insertion. True Fail Safe (MAX14841E) The MAX14841E 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 the case if the receiver input threshold is between -10mV and -200mV. RO is logic-high if the differential receiver input voltage VOD is greater than or equal to -10mV. The MAX14840E features symmetrical fail-safe and larger receiver hysteresis, providing improved noise rejection and improved recovered signals in high-speed and long cable applications. The MAX14841E has true failsafe receiver inputs guaranteeing a logic-high receiver output when inputs are shorted or open. All devices have a 1-unit load receiver input impedance, allowing up to 32 transceivers on the bus. Hot-Swap Capability Hot-Swap Inputs When circuit boards are inserted into a hot or powered backplane, disturbances to the enable inputs and differ ential receiver inputs can lead to data errors. Upon initial circuit board insertion, the processor undergoes its powerup sequence. During this period, the processor output drivers are high impedance and are unable to drive the DE and RE inputs of the MAX14840E/MAX14841E to a defined logic level. Leakage currents up to 10FA from the high-impedance 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 MAX14840E/MAX14841E have hot-swap inputs that avoid these potential problems. The MAX14840E/MAX14841E transceivers draw 1.5mA (typ) supply current when unloaded or when fully loaded with the drivers disabled. Symmetrical Fail Safe (MAX14840E) At high data rates and with long cable lengths, the signal at the end of the cable is attenuated and distorted due to the lowpass characteristic of the transmission line. Under these conditions, fail-safe RS-485 receivers, which have offset threshold voltages, produce recovered signals with uneven mark-space ratios. The MAX14840E has symmetrical receiver thresholds, as shown in Figure 9. This produces near even mark-space ratios at the receiver's output (RO). The MAX14840E also has higher receiver hysteresis than the MAX14841E and most other RS-485 transceivers. This results in higher receiver noise tolerance. 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. Symmetrical fail safe means that the receiver's output (RO) remains at the same logic state that it was before the differential input voltage VOD went to 0V. Under RO -200mV +200mV -10mV +10mV VTHF VOD VTHP VTHP Figure 9. Symmetrical Hysteresis 12 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers For RE, there is a complementary circuit employing two pMOS devices pulling RE to VCC. 35kV ESD Protection 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 MAX14840E family of devices have extra protection against static electricity. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD event, the MAX14840E/MAX14841E keep working without latchup or damage. ESD protection can be tested in various ways. The transmitter outputs and receiver inputs of the MAX14840E/ MAX14841E are characterized for protection to the following limits: * Q35kV HBM * Q 20kV using the Air Gap Discharge method specified in IEC 61000-4-2 * Q 12kV using the Contact Discharge method specified in IEC 61000-4-2 VCC 15Fs TIMER TIMER DE DRIVER ENABLE (HOT SWAP) 5.6kI 100FA M1 1mA M2 Figure 10. Simplified Structure of the Driver Enable Pin (DE) ______________________________________________________________________________________ 13 MAX14840E/MAX14841E How-Swap Input Circuitry The MAX14840E/MAX14841E DE and RE enable inputs feature hot-swap capability. At the input, there are two nMOS devices, M1 and M2 (Figure 10). When VCC ramps from 0V, 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 15s, 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. 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 11 shows the HBM, and Figure 12 shows the current waveform it generates when discharged into a low-impedance state. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a 1.5kI resistor. IEC 61000-4-2 The IEC 61000-4-2 standard covers ESD testing and performance of finished equipment. However, it does not specifically refer to integrated circuits. The MAX14840E/ MAX14841E family of devices helps you design equipment to meet IEC 61000-4-2, without the need for additional ESD protection components. RC 1MI CHARGE CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE CS 100pF The major 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 model. Hence, the ESD withstand voltage measured to IEC 61000-4-2 is generally lower than that measured using the HBM. Figure 13 shows the IEC 61000-4-2 model, and Figure 14 shows the current waveform for IEC 61000-4-2 ESD Contact Discharge test. Applications Information High-Speed Operation The MAX14840E and MAX14841E are high-performance RS-485 transceivers supporting data rates up to 40Mbps. Driver Output Protection Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. Current limit on the output stage provides RC 50M TO 100M RD 1.5kI CHARGE CURRENT LIMIT RESISTOR DISCHARGE RESISTANCE DEVICE UNDER TEST STORAGE CAPACITOR Figure 11. Human Body ESD Test Model IP 100% 90% IR HIGHVOLTAGE DC SOURCE Cs 150pF RD 330 DISCHARGE RESISTANCE STORAGE CAPACITOR DEVICE UNDER TEST Figure 13. IEC 61000-4-2 ESD Test Model I 100% 90% PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) IPEAK MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers AMPERES 36.8% 10% 0 10% 0 tRL TIME tDL CURRENT WAVEFORM Figure 12. Human Body current Waveform tR = 0.7ns TO 1ns t 30ns 60ns Figure 14. IEC 61000-4-2 ESD Generator Current Waveform 14 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers 120 DE B B DI D D DI DE RO A B A B A A R R RO RE RE R R D D MAX14840E MAX14841E DI DE RO RE DI DE RO RE Figure 15. Typical Half-Duplex RS-485 Network immediate protection against short circuits over the whole common-mode voltage range (see the Typical Operating Characteristics). Additionally, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature exceeds +160NC (typ). Low-Power Shutdown Mode Low-power shutdown mode is initiated by bringing RE high and DE low. In shutdown, the devices draw less than 10FA of supply current. RE and DE can 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 800ns, the parts are guaranteed to enter shutdown. Chip Information PROCESS: 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 PACKAGE CODE DOCUMENT NO. 8 SO S8+4 21-0041 8 TDFN-EP T833+2 21-0137 Typical Applications The MAX14840E/MAX14841E transceivers are designed for bidirectional data communications on multipoint bus transmission lines. Figure 15 shows a typical network application circuit. To minimize reflections, terminate the line at both ends with its characteristic impedance and keep stub lengths off the main line as short as possible. 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 (c) 2010 Maxim Integrated Products 15 Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX14840E/MAX14841E 120