MAX13488EESA+T

EVALUATION KIT AVAILABLE Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E General Description Benefits and Features The MAX13487E/MAX13488E +5V, half-duplex, ±15kV ESD-protected RS-485/RS-422-compatible transceivers feature one driver and one receiver. The MAX13487E/ MAX13488E include a hot-swap capability to eliminate false transitions on the bus during power-up or live insertion. The MAX13487E/MAX13488E feature Maxim’s proprietary AutoDirection control. This architecture makes the devices ideal for applications, such as isolated RS-485 ports, where the driver input is used in conjunction with the driver-enable signal to drive the differential bus. The MAX13487E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission up to 500kbps. The MAX13488E driver slew rate is not limited, allowing transmit speeds up to 16Mbps. The MAX13487E/MAX13488E feature a 1/4-unit load receiver input impedance, allowing up to 128 transceivers on the bus. These devices are intended for halfduplex communications. All driver outputs are protected to ±15kV ESD using the Human Body Model. The MAX13487E/MAX13488E are available in an 8-pin SO package. The devices operate over the extended -40°C to +85°C temperature range. • AutoDirection Saves Space and BOM Cost • AutoDirection Enables Driver Automatically on Transmission, Eliminating an Opto or Other Discrete Means of Isolation • 8-Pin SO Package • Robust Protection Features for Telecom, Industrial, and Isolated Applications • Hot-Swap Capability to Eliminate False Transitions on the Bus During Power-Up or Live Insertion • Extended ESD Protection for RS-485 I/O Pins (±15kV Human Body Model) • Options Optimize Designs for Speed or Errorless Data Transmission • Enhanced Slew-Rate Limiting Facilitates ErrorFree Data Transmission (MAX13487E) • High-Speed Version (MAX13488E) Allows for Transmission Speeds Up to 16Mbps • 1/4-Unit Load, Allowing Up to 128 Transceivers on the Bus Functional Diagram MAX13487E MAX13488E Applications Isolated RS-485 Interfaces 1 RO 2 RE VCC 8 + R - Utility Meters RE Industrial Controls Industrial Motor Drives 3 Automated HVAC Systems SHDN - VDT B 7 COM + Ordering Information/ Selector Guide PART PIN-PACKAGE RI DI A 6 STATE MACHINE DE SLEW-RATE LIMITED MAX13487EESA+ 8 SO Yes MAX13488EESA+ 8 SO No 4 D DI GND 5 +Denotes a lead(Pb)-free/RoHS-compliant package. Note: All devices operate over the -40°C to +85°C temperature range. Pin Configuration/Typical Application Circuit appear at end of data sheet. 19-0740; Rev 1; 2/15 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Absolute Maximum Ratings (All voltages referenced to GND.) Supply Voltage VCC ...............................................................+6V SHDN, RE, DI..............................................................-0.3V to +6 A, B........................................................................... -8V to +13V Short-Circuit Duration (RO, A, B) to GND ..................Continuous Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering 10s) ..................................+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 Differential Driver Output VOD RDIFF = 100Ω, Figure 1 2.0 RDIFF = 54Ω, Figure 1 1.5 VCC V No load VCC Driver Common-Mode Output Voltage VOC RL = 100Ω or 54Ω, Figure 1 Driver Disable Threshold VDT Figure 2 (Note 2) Input-High Voltage VIH DI, SHDN, RE Input-Low Voltage VIL DI, SHDN, RE 0.8 V Input Current IIN DI, SHDN, RE ±1 µA Driver Short-Circuit Output Current (Note 3) IOSD Driver Short-Circuit Foldback Output Current (Note 3) IOSDF VCC / 2 +0.6 3 V +1 V 2.0 V 0V ≤ VOUT ≤ +12V +50 +250 -7V ≤ VOUT ≤ 0V -250 -50 mA (VCC - 1V) ≤ VOUT ≤ +12V 20 mA -7V ≤ VOUT ≤ 0V -20 RECEIVER Input Current (A and B) IA, B DI = VCC, VCC = GND or +5V Receiver Differential Threshold Voltage VTH -7V ≤ VCM ≤ +12V Receiver Input Hysteresis ΔVTH VA + VB = 0V VIN = +12V VIN = -7V 250 -200 -200 +200 25 µA mV mV VCC 1.5 Output-High Voltage VOH IO = -1.6mA, VA - VB > VTH Output-Low Voltage VOL IO = 1mA, VA - VB < -VTH 0.4 V Tri-State Output Current at Receiver IOZR 0V ≤ VO ≤ VCC ±1 µA Receiver Input Resistance RIN -7V ≤ VCM ≤ +12V 48 Receiver Output Short-Circuit Current IOSR 0V ≤ VRO ≤ VCC ±7 www.maximintegrated.com V kΩ ±95 mA Maxim Integrated | 2 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Electrical Characteristics (continued) (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 POWER SUPPLY Supply Voltage VCC Supply Current ICC Shutdown Supply Current ISHDN 5.25 V SHDN = 1, RE = 0, no load 4.75 4.5 mA SHDN = 0 10 µA ESD PROTECTION ESD Protection (A, B) ESD Protection (All Other Pins) Air Gap Discharge IEC 61000-4-2 (MAX13487E) ±15 Human Body Model ±15 Human Body Model ±2 kV kV Switching Characteristics—MAX13487E (VCC = +5V ±5%, 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 Driver Propagation Delay Driver Differential Output Rise or Fall Time tDPLH tDPHL tHL tLH RL = 110Ω, CL = 50pF, Figures 2 and 3 RL = 110Ω, CL = 50pF, Figures 2 and 3 Maximum Data Rate Driver Disable Delay 200 1000 200 1000 200 900 200 900 500 tDDD ns ns kbps Figure 3 2500 ns Driver Enable from Shutdown to Output High tDZH(SHDN) Figure 4 5.5 µs Driver Enable from Shutdown to Output Low tDZL(SHDN) Figure 4 5.5 µs 700 ns Time to Shutdown tSHDN 50 340 RECEIVER Receiver Propagation Delay Receiver Output Skew tRPLH tRPHL tRSKEW 80 CL = 15pF, Figures 5 and 6 80 CL = 15pF, Figure 6 Maximum Data Rate 13 500 ns ns kbps Receiver Enable to Output High tRZH Figure 7 50 ns Receiver Enable to Output Low tRZL Figure 7 50 ns Receiver Disable Time from High tRHZ Figure 7 50 ns Receiver Disable Time from Low tRLZ Figure 7 50 ns Receiver Enable from Shutdown to Output High Figure 8 2200 ns (SHDN) www.maximintegrated.com tRZH Maxim Integrated | 3 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Switching Characteristics—MAX13487E (continued) (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER Receiver Enable from Shutdown to Output Low Receiver Enable Delay Time to Shutdown SYMBOL CONDITIONS tRZL (SHDN) Figure 8 tRED Figure 3 tSHDN MIN 50 TYP 340 MAX UNITS 2200 ns 70 ns 700 ns MAX UNITS Switching Characteristics—MAX13488E (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP DRIVER Driver Propagation Delay Driver Differential Output Rise or Fall Time tDPLH tDPHL tHL tLH 50 15 RL = 110Ω, CL = 50pF, Figures 2 and 3 Maximum Data Rate Driver Disable Delay 50 RL = 110Ω, CL = 50pF, Figures 2 and 3 15 16 ns Mbps Figure 3 70 ns Driver Enable from Shutdown to Output High tDZH(SHDN) Figure 4 2.2 µs Driver Enable from Shutdown to Output Low tDZL(SHDN) Figure 4 2.2 µs 700 ns Time to Shutdown tDDD ns tSHDN 50 340 RECEIVER Receiver Propagation Delay Receiver Output Skew tRPLH tRPHL tRSKEW 80 CL = 15pF, Figures 5 and 6 80 CL = 15pF, Figure 6 Maximum Data Rate 13 16 ns ns Mbps Receiver Enable to Output High tRZH Figure 7 50 ns Receiver Enable to Output Low tRZL Figure 7 50 ns Receiver Disable Time from High tRHZ Figure 7 50 ns Receiver Disable Time from Low tRLZ Figure 7 50 ns Receiver Enable from Shutdown to Output High Figure 8 2200 ns (SHDN) www.maximintegrated.com tRZH Maxim Integrated | 4 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Switching Characteristics—MAX13488E (continued) (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL Receiver Enable from Shutdown to Output Low CONDITIONS MIN TYP MAX UNITS tRZL (SHDN) Figure 8 2200 ns tRED Figure 3 70 ns 700 ns Receiver Enable Delay Time to Shutdown tSHDN 50 340 Note 1: All currents into the device are positive. All currents out of the device are negative. All voltages referred to device ground, unless otherwise noted. Note 2: This is a differential voltage from A to B that the driving device must see on the bus to disable its driver. Note 3: The short-circuit output current applied 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 = +5.0V, TA = +25°C, unless otherwise noted.) 3.6 3.4 21 14 7 3.2 -15 10 35 60 MAX13487Etoc03 30 20 0 1 0 85 2 3 4 0 5 1 2 3 4 TEMPERATURE (°C) OUTPUT-HIGH VOLTAGE (V) OUTPUT-LOW VOLTAGE (V) RECEIVER OUTPUT-HIGH VOLTAGE vs. TEMPERATURE RECEIVER OUTPUT-LOW VOLTAGE vs. TEMPERATURE DIFFERENTIAL OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE 5.0 4.8 4.6 4.4 IO = 1mA 0.4 0.3 0.2 0.1 5 80 MAX13487Etoc06 5.2 0.5 OUTPUT CURRENT (mA) IO = 1mA MAX13487Etoc05 MAX13487Etoc04 5.4 OUTPUT-LOW VOLTAGE (V) -40 40 10 0 3.0 OUTPUT-HIGH VOLTAGE (V) 50 OUTPUT CURRENT (mA) 28 OUTPUT CURRENT (mA) 3.8 60 MAX13487Etoc02 NO LOAD SUPPLY CURRENT (mA) 35 MAX13487Etoc01 4.0 OUTPUT CURRENT vs. RECEIVER OUTPUT-LOW VOLTAGE OUTPUT CURRENT vs. RECEIVER OUTPUT-HIGH VOLTAGE SUPPLY CURRENT vs. TEMPERATURE 60 40 20 4.2 0 4.0 -40 -15 10 35 TEMPERATURE (°C) www.maximintegrated.com 60 85 0 -40 -15 10 35 TEMPERATURE (°C) 60 85 0 1 2 3 4 5 OUTPUT VOLTAGE (V) Maxim Integrated | 5 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Typical Operating Characteristics (continued) (VCC = +5.0V, TA = +25°C, unless otherwise noted.) 2.0 1.5 1.0 0.5 60 40 -15 10 35 60 60 40 0 -7 -6 -5 -4 -3 -2 -1 0 85 80 20 0 -40 1 2 3 4 0 5 2 4 6 8 10 12 OUTPUT-LOW VOLTAGE (V) SHUTDOWN CURRENT vs. TEMPERATURE DRIVER PROPAGATION vs. TEMPERATURE (MAX13487E) DRIVER PROPAGATION vs. TEMPERATURE (MAX13487E) 7 6 5 4 3 2 RL = 10kΩ 800 tDPLH 600 400 200 tDPHL 1 0 600 DRIVER PROPAGATION DELAY (ns) 8 1000 DRIVER PROPAGATION DELAY (ns) MAX13487Etoc10 9 0 -40 -15 10 35 60 85 MAX13487Etoc12 OUTPUT-HIGH VOLTAGE (V) MAX13487Etoc11 TEMPERATURE (°C) 10 RL = 110Ω tDPLH 500 400 300 200 tDPHL 100 0 -40 -15 10 35 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) DRIVER PROPAGATION vs. TEMPERATURE (MAX13488E) DRIVER PROPAGATION vs. TEMPERATURE (MAX13488E) RECEIVER PROPAGATION vs. TEMPERATURE (MAX13487E) 25 20 15 10 tDPLH 5 30 RL = 110Ω 25 20 15 10 tDPLH -15 10 35 TEMPERATURE (°C) www.maximintegrated.com 60 85 tRPHL 30 15 tRPLH tDPHL 0 0 -40 45 5 tDPHL 0 60 MAX13487Etoc15 RL = 10kΩ DRIVER PROPAGATION DELAY (ns) 30 MAX13487Etoc14 TEMPERATURE (°C) MAX13487Etoc13 TEMPERATURE (°C) PROPAGATION DELAY (ns) SHUTDOWN CURRENT (μA) 80 20 0 DRIVER PROPAGATION DELAY (ns) 100 OUTPUT CURRENT (mA) 100 OUTPUT CURRENT (mA) 2.5 120 MAX13487Etoc08 RDIFF = 54Ω DIFFERENTIAL OUTPUT VOLTAGE (V) 120 MAX13487Etoc07 3.0 OUTPUT CURRENT vs. TRANSMITTER OUTPUT-LOW VOLTAGE OUTPUT CURRENT vs. TRANSMITTER OUTPUT-HIGH VOLTAGE MAX13487Etoc09 DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) Maxim Integrated | 6 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Typical Operating Characteristics (continued) (VCC = +5.0V, TA = +25°C, unless otherwise noted.) 30 MAX13487Etoc18 MAX13487Etoc16 RECEIVER PROPAGATION (ns) 40 DRIVER PROPAGATION (16Mbps) (MAX13488E) DRIVER PROPAGATION (500kbps) (MAX13487E) MAX13487Etoc17 RECEIVER PROPAGATION vs. TEMPERATURE (MAX13488E) DI 2V/div DI 2V/div tRPLH 20 tRPHL A-B 5V/div A-B 5V/div 10 WAVEFORM INTENSITY: 68% 0 -40 -15 10 35 60 85 10ns/div 400ns/div TEMPERATURE (°C) MAX13487Etoc19 MAX13487Etoc20 DRIVING 16nF (19.2kbps) (MAX13487E) RECEIVER PROPAGATION (16Mbps) (MAX13488E) B 2V/div DI 2V/div A 2V/div A-B 5V/div RO 2V/div 10μs/div 10ns/div MAX13487Etoc21 MAX13487Etoc22 DRIVING 16nF (750kbps) (MAX13488E) DRIVING 16nF (19.2kbps) (MAX13488E) DI 2V/div A-B 5V/div A-B 5V/div 10μs/div www.maximintegrated.com DI 2V/div 400ns/div Maxim Integrated | 7 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Test Circuits and Waveforms A RDIFF RL 2 DI VOD CL A VCC GND VID B RDIFF CL RL 2 VOC B Figure 2. Driver-Timing Test Circuit Figure 1. Driver DC Test Load RE = VCC VCC f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns 1.5V DI 1.5V 0 tDPLH 1/2 VO tDPHL B VO A 1/2 VO RO O tDDD, tRED (RO PULLED LOW) VDIFF = V(A) - V(B) VO VDIFF 90% 90% 0 10% 10% -VO tLH tHL Figure 3. Driver Propagation Delays www.maximintegrated.com Maxim Integrated | 8 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Test Circuits and Waveforms (continued) VCC 1.5V SHDN 0 tDZL(SHDN) A, B 500Ω OUTPUT UNDER TEST S1 CL VCC 2.3V OUTPUT NORMALLY LOW VOL S2 OUTPUT NORMALLY HIGH A, B 2.3V 0 tDZH(SHDN) Figure 4. Driver Enable and Disable Times B R VID ATE RECEIVER OUTPUT A Figure 5. Receiver-Propagation-Delay Test Circuit A f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns 1V -1V B tRPLH tRPHL VOH RO 1.5V VOL 1.5V tRSKEW = | tRPHL - tRPLH | Figure 6. Receiver Propagation Delays www.maximintegrated.com Maxim Integrated | 9 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Test Circuits and Waveforms (continued) VCC RE 1.5V 1.5V 0 tRZL(SHDN), tRZL tRHZ VCC RO 2.3V 0 VOH + 0.5V OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH VCC 2.3V RO VOH + 0.5V 0 tRZH(SHDN), tRZH DI = 0V tRHZ Figure 7. Receiver Enable and Disable Times VCC 1.5V SHDN 0 tRZL(SHDN) VCC 500Ω RO CL S1 VCC 2.3V RO 0 S2 OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH VCC 2.3V RO 0 tRZH(SHDN) DI = 1 Figure 8. Receiver Enable Time from Shutdown www.maximintegrated.com Maxim Integrated | 10 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Pin Description PIN NAME 1 RO Receiver Output. When receiver is enabled and V(A) - V(B) > +200mV, RO is high. If V(A) - V(B) < -200mV, RO is low. 2 RE Receiver Output Enable. Drive RE low to enable the RO. Drive RE high to let the AutoDirection circuit control the receiver. RE is a hot-swap input (see the Hot-Swap Capability section for more details). 3 SHDN Shutdown. Drive SHDN high to let the device operate in normal operation. Drive SHDN low to put the part in shutdown. 4 DI Driver Input. Drive DI low to force noninverting output low and inverting output high. Drive DI high to force noninverting output high and inverting output low. DI is an input to the internal state machine that automatically enables and disables the driver. See the Function Tables and General Description for more information. DI is a hot-swap input (see the Hot-Swap Capability section for more details). 5 GND 6 A 7 B 8 VCC FUNCTION Ground Noninverting Receiver Input and Noninverting Driver Output Inverting Receiver Input and Inverting Driver Output Positive Supply, VCC = +5V ±5%. Bypass VCC to GND with a 0.1µF capacitor. Function Tables TRANSMITTING INPUTS OUTPUTS SHDN DI A-B > VDT ACTION A 1 0 X Turn driver ON 0 1 1 1 False If driver was OFF, keep it OFF HIGH IMPEDANCE HIGH IMPEDANCE 1 1 False If driver was ON, keep it ON 1 0 1 1 True Turn driver OFF HIGH IMPEDANCE HIGH IMPEDANCE 0 X X X B SHUTDOWN RECEIVING INPUTS OUTPUT SHDN RE A-B DRIVER STATE RECEIVER STATE RO 1 0 ≥+200mV X ON 1 1 0 ≤-200mV X ON 0 1 1 X ON OFF HIGH IMPEDANCE 1 1 ≥+200mV OFF ON 1 1 1 ≤-200mV OFF ON 0 0 X X X X SHUTDOWN X = Don’t care, shutdown mode, driver, and receiver outputs are in high impedance. www.maximintegrated.com Maxim Integrated | 11 MAX13487E/MAX13488E Detailed Description The MAX13487E/MAX13488E half-duplex, high-speed transceivers for RS-485/RS-422 communication contain one driver and one receiver. The MAX13487E/ MAX13488E feature a hot-swap capability allowing line insertion without erroneous data transfer (see the HotSwap Capability section). The MAX13487E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission up to 500kbps. The MAX13488E driver slew rate is not limited, making data throughput of up to 16Mbps possible. AutoDirection Circuitry Internal circuitry in the MAX13487E/MAX13488E, in conjunction with an external pullup resistor on A and pulldown resistor on B (see Typical Application Circuit ), act to automatically disable or enable the driver and receiver to keep the bus in the correct state. This AutoDirection circuitry consists of a state machine and an additional receive comparator that determines whether this device is trying to drive the bus, or another node on the network is driving the bus. The internal state machine has two inputs: • DI • The current state of A-B (determined by a dedicated differential comparator) The state machine also has two outputs: • DRIVER_ENABLE—Internal signal that enables and disables the driver • RECEIVER_ENABLE—Internal signal that is the inverse of the DRIVER_ENABLE signal, but it can be overridden by an external pin When DI is low, the device always drives the bus low. When DI is high, the device drives the bus for a short time, then disables the driver and allows the external pullup/pulldown resistors to hold the bus in the high state (A-B > 200mV). During each low-to-high transition of DI, the driver stays enabled until (A-B) > VDT, and then disables the driver, letting the pullup/pulldown resistors hold the A and B lines in the correct state. Pullup and Pulldown Resistors The pullup and pulldown resistors on the A and B lines are required for proper operation of the device although their exact value is not critical. They function to hold the bus in the high state (A-B > 200mV) following a low-to-high transition. Sizing of these resistors is determined in the same way as when using any other RS-485 driver and depends on how the line is terminated and how many nodes are on the bus. The most www.maximintegrated.com Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control important factor when sizing these resistors is to guarantee that the idle voltage on the bus (A-B) is greater than 200mV in order to remain compatible with standard RS-485 receiver thresholds. Idle State When not transmitting data, the MAX13487E/ MAX13488E require the DI input be driven high to remain in the idle state. A conventional RS-485 transceiver has DE and RE inputs that are used to enable and disable the driver and receiver. However, the MAX13487E/MAX13488E does not have a DE input, and instead uses an internal state machine to enable and disable the drivers. DI must be driven high in order to go to the idle state. Hot-Swap Capability Hot-Swap Inputs When circuit boards are inserted into a hot or powered back plane, differential disturbances to the data bus can lead to data errors. Upon initial circuit-board insertion, the data communication processor undergoes its own power-up sequence. During this period, the processor’s logic-output drivers are high impedance and are unable to drive the DI and RE inputs of these devices to a defined logic level. Leakage currents up to ±10µA from the high-impedance state of the processor’s logic drivers could cause standard CMOS enable inputs of a transceiver to drift to an incorrect logic level. Additionally, parasitic circuit-board capacitance could cause coupling of VCC or GND to the enable inputs. Without the hot-swap capability, these factors could improperly enable the transceiver’s driver. To overcome both these problems, two different pullup switches (strong and weak) are turned on during the power-up. When VCC rises, an internal power-up signal enables a strong pullup circuit. It holds DI and RE high with 1mA for 15µs. Once the timeout is expired, this strong pullup is switched off. A weak pullup (100µA) remains active to overcome leakage on the pin. This second weak pullup disappears as soon as the microcontroller forces a low state on these pins. Therefore, in normal operation (after the first activation), these pins can be considered as high-impedance pins (CMOS inputs) without any pullup circuitry. The AutoDirection state machine is initialized, forcing the driver disabled. The receiver is enabled in AutoDirection mode. Hot-Swap Input Circuitry The enable inputs feature hot-swap capability. At the input there are two pMOS devices, M1 and M2 (Figure 9). When VCC ramps from zero, an internal 15µs timer turns Maxim Integrated | 12 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E on M2 and sets the SR latch, which also turns on M1. Transistors M2, a 1.5mA current source, and M1, a 500µA current source, pull RE to VCC through a 5kΩ resistor. M2 is designed to pull RE to the disabled state against an external parasitic capacitance up to 100pF that can drive RE high. After 15µs, the timer deactivates M2 while M1 remains on, holding DI high against three-state leakages that can drive RE low. 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, RE reverts to a standard, high-impedance CMOS input. Whenever VCC drops below 1V, the hot-swap input is reset. DI has similar hot-swap circuitry. VCC 15μs TIMER SR LATCH TIMER ±15kV ESD Protection As with all Maxim devices, 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 MAX13487E/MAX13488E have extra protection against static electricity. Maxim’s engineers have developed state-of-the-art structures to protect these pins against ESD of ±15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD event, the MAX13487E/MAX13488E keep working without latchup or damage. ESD protection can be tested in various ways. The transmitter outputs and receiver inputs of the MAX13487E/MAX13488E are characterized for protection to the following limits: • ±15kV using the Human Body Model • ±15kV using the Air Gap Discharge Method specified in IEC 61000-4-2 (MAX13487E only) 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 10a shows the Human Body Model, and Figure 10b 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 test device through a 1.5kΩ 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 MAX13487E/MAX13488E help you design equipment to www.maximintegrated.com 5kΩ RE (HOT SWAP) RE 100μA 500μA M2 M1 VCC Figure 9. Simplified Structure of the Receiver Enable Pin (RE) meet IEC 61000-4-2 without the need for additional ESD-protection components. The major difference between tests done using the Human Body Model 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 Human Body Model. Figure 10c shows the IEC 61000-4-2 model, and Figure 10d shows the current waveform for IEC 61000-4-2 ESD Contact Discharge test. Machine Model The machine model for ESD tests all pins using a 200pF storage capacitor and zero discharge resistance. The objective is to emulate the stress caused when I/O pins are contacted by handling equipment during test and assembly. Of course, all pins require this protection, not just RS-485 inputs and outputs. The Air-Gap test involves approaching the device with a charged probe. The Contact-Discharge method connects the probe to the device before the probe is energized. Maxim Integrated | 13 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E RC 1MΩ CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE Cs 100pF RD 1500Ω RC 50MΩ TO 100MΩ DISCHARGE RESISTANCE CHARGE-CURRENTLIMIT RESISTOR DEVICE UNDER TEST STORAGE CAPACITOR Figure 10a. Human Body ESD Test Model IP 100% 90% Cs 150pF DISCHARGE RESISTANCE STORAGE CAPACITOR DEVICE UNDER TEST Figure 10c. IEC 61000-4-2 ESD Test Model I 100% 90% PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) IPEAK Ir HIGHVOLTAGE DC SOURCE RD 330Ω AMPS 36.8% 10% 0 10% 0 tRL TIME tr = 0.7ns TO 1ns tDL CURRENT WAVEFORM t 30ns 60ns Figure 10b. Human Body Current Waveform Figure 10d. IEC 61000-4-2 ESD Generator Current Waveform Applications Information Low-Power Shutdown Mode 128 Transceivers on the Bus The standard RS-485 receiver input impedance is 12kΩ (1-unit load), and the standard driver can drive up to 32-unit loads. The MAX13487E/MAX13488E have a 1/4unit load receiver input impedance (48kΩ), allowing up to 128 transceivers to be connected in parallel on one communication line. Any combination of these devices, as well as other RS-485 transceivers with a total of 32unit loads or fewer, can be connected to the line. Reduced EMI and Reflections The MAX13487E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps. Low-power shutdown mode is initiated by bringing SHDN low. In shutdown, the devices draw a maximum of 10µA of supply current. The devices are guaranteed not to enter shutdown if SHDN is low for less than 50ns. If the inputs are in this state for at least 700ns, the devices are guaranteed to enter shutdown. Enable times tZH and tZL (see the Switching Characteristics section) assume the devices were not in a lowpower shutdown state. Enable times t ZH(SHDN) and tZL(SHDN) assume the devices were in shutdown state. It takes drivers and receivers longer to become enabled from low-power shutdown mode (tZH(SHDN), tZL(SHDN)) than from driver/receiver-disable mode (tZH, tZL). Line Length The RS-485/RS-422 standard covers line lengths up to 4000ft. www.maximintegrated.com Maxim Integrated | 14 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E VCC DI D VCC Rt SHDN RO RE D Rt VCC SHDN VCC R R MAX13487E MAX13488E R RO RE R D D DI DI SHDN RO RE DI SHDN RO RE Figure 11. Typical Half-Duplex RS-485 Network Typical Applications The MAX13487E/MAX13488E transceivers are designed for half-duplex, bidirectional data communications on multipoint bus transmission lines. Figure 11 shows a typical network application. 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 MAX13487E is more tolerant of imperfect termination. Circuit shows an isolated RS-485 interface using the MAX13487E/MAX13488E. The transceiver is powered separately from the controlling circuitry. The AutoDirection feature of the MAX13487E/MAX13488E (see the AutoDirection Circuitry section), replaces an external relay allowing faster switching speeds, no contact bounce, better reliability, and better electrical isolation. The MAX13487E/MAX13488E only require two optocouplers to electrically isolate the transceiver. Isolated RS-485 Interface An isolated RS-485 interface electrically isolates different nodes on the bus to protect the bus from problems due to high common-mode voltages that exceed the RS-485 common-mode voltage range, conductive noise, and ground loops. The Typical Application www.maximintegrated.com Chip Information PROCESS: BiCMOS Maxim Integrated | 15 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Pin Configuration/Typical Application Circuit VSYS RXD VISO VCC 0.1μF RO VISO VISO RE VSYS SHDN DI + 1 8 R 2 7 3 6 4 D A VCC 5 GND SO TXD B Rt Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 OUTLINE NO. LAND PATTERN NO. 8 SO S8+2 21-0041 90-0096 www.maximintegrated.com Maxim Integrated | 16 Half-Duplex RS-485-/RS-422Compatible Transceiver with AutoDirection Control MAX13487E/MAX13488E Revision History PAGES CHANGED REVISION NUMBER REVISION DATE 0 1/07 Initial release — 1 2/15 Added the Benefits and Features section 1 DESCRIPTION For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2015 Maxim Integrated Products, Inc. | 17