EVALUATION KIT AVAILABLE MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables General Description Benefits and Features The MAX22500E features integrated preemphasis circuitry that extends the distance and increases the data rate of reliable communication by reducing inter-symbol interference (ISI) caused by long cables. The MAX22500E features a flexible logic interface down to 1.6V. ●● Integrated Protection Increases Robustness • -15V to +15V Common Mode Range • ±15kV ESD Protection (Human Body Model) • ±7kV IEC 61000-4-2 Air-Gap ESD Protection • ±6kV IEC 61000-4-2 Contact Discharge ESD Protection • Driver Outputs are Short-Circuit Protected The MAX22500E/MAX22501E half-duplex ESD-protected RS-485/RS-422 transceivers are optimized for highspeed (up to 100Mbps) communication over long cables. These transceivers feature integrated hot-swap protection and a fail-safe receiver, ensuring a logic-high on the receiver output when input signals are shorted or open for longer than 10μs (typ). The MAX22501E operates without preemphasis and is powered from a 3V to 5.5V supply. The MAX22500E is available in a 10-pin TDFN-EP package. The MAX22501E is available in a 8-pin TDFN-EP package. Both transceivers operate over the -40°C to +125°C ambient temperature range. Applications ●● Motion Control ●● High-Speed Operation Over Long Distances • Up to 100Mbps Data Rate • Integrated Preemphasis Extends Cable Length (MAX22500E) • High Receiver Sensitivity • Wide Receiver Bandwidth • Symmetrical Receiver Thresholds ●● Flexibility for Many Different Applications • 3V to 5.5V Supply Range • Low Voltage Logic Supply Down to 1.6V (MAX22500E) • Low 5μA (max) Shutdown Current • Available in 8-pin or 10-pin TDFN Package • -40°C to +125°C Operating Temperature Range ●● Encoder Interfaces ●● Field Bus Networks ●● Industrial Control Systems Ordering Information appears at end of data sheet. ●● Backplane Busses Simplified Block Diagram VL VCC RO DI PSET RO R RE DE SHUTDOWN B RE A DE DI D MAX22500E GND 19-100073; Rev 0; 6/17 VCC R B SHUTDOWN D MAX22501E GND A MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Absolute Maximum Ratings VCC.........................................................................-0.3 V to +6 V RE, DE, DI, VL .....................................................-0.3 V to +6 V RO (MAX22500E only)............................... -0.3 V to (VL + 0.3) V RO (MAX22501E only).............................. -0.3V to (VCC + 0.3)V PSET......................................................... -0.3 V to (VCC+0.3) V A, B..........................................................................-15V to +15V Short-Circuit Duration (RO, A, B) to GND..................Continuous Continuous Power Dissipation (TA = +70°C) (8-Pin TDFN (derate 24.4mW/°C above +70°C) )...........................1951mW Continuous Power Dissipation (TA = +70°C) (10-Pin TDFN (derate 24.4mW/°C above +70°C) )...........................1951mW Operating Temperature Range ......................... -40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range ............................ -65°C to +150°C Lead Temperature (Soldering 10sec) .............................. +300°C Reflow Temperature ........................................................ +270ºC 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. Package Information TDFN8 PACKAGE CODE T833-2 Outline Number 21-0137 Land Pattern Number 90-0059 Thermal Resistance, Single-Layer Board: Junction to Ambient (θJA) 54°C/W Junction to Case (θJC) 8°C/W Thermal Resistance, Four-Layer Board: Junction to Ambient (θJA) 41°C/W Junction to Case (θJC) 8°C/W TDFN10 PACKAGE CODE T1033-2 Outline Number 21-0137 Land Pattern Number 90-0061 Thermal Resistance, Single-Layer Board: Junction to Ambient (θJA) 54°C/W Junction to Case (θJC) 9°C/W Thermal Resistance, Four-Layer Board: Junction to Ambient (θJA) 41°C/W Junction to Case (θJC) 9°C/W 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 thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. www.maximintegrated.com Maxim Integrated │ 2 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Electrical Characteristics (VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2)) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS POWER Supply Voltage VCC MAX22500E Preemphasis disabled 3.0 Preemphasis enabled 4.5 5 5.5 MAX22500E 12.7 16.5 MAX22501E 4 5.6 MAX22501E Supply Current Shutdown Supply Current ICC ISHDN DE = high, RE= low, no load 5.5 3.0 5.5 5 DE = low, RE= high Logic Supply Voltage VL MAX22500E only Logic Supply Current IL MAX22500E only, no load on RO V 1.6 16.4 mA µA VCC V 23 µA DRIVER Differential Driver Output RL = 54Ω 1.5 RL = 100Ω 2.0 RL= 54Ω 1.33 1.37 1.41 RL= 100Ω 1.33 1.37 1.41 VOD Figure 1, Figure 2 Differential Driver Preemphasis Ratio DPRE MAX22500E only, preemphasis enabled, 4.5V ≤ VCC ≤ 5.5V (Note 3) Change in Magnitude of Differential Output Voltage ΔVOD RL = 54Ω, Figure 1 (Note 4) VOC RL = 54Ω, Normal mode and preemphasis, Figure 1 Driver Common-Mode Output Voltage Change In Magnitude of Common-Mode Voltage ΔVOC V VCC/2 RL = 100Ω or 54Ω, Figure 1 (Note 4) Single-Ended Driver Output High VOH A or B output, IOUT = -20mA Single-Ended Driver Output Low VOL A or B output, IOUT = +20mA Differential Output Capacitance COD DE = RE= high, f = 4MHz Driver Short-Circuit Output Current |IOST| -15V ≤ VOUT ≤ +15V Input Current (A and B) IA,B DE = GND, VCC = GND, +3.6V or 5.5V Differential Input Capacitance CA,B Between A and B, DE = GND, f = 2MHz Common Mode Voltage Range VCM V/V 0.2 V 3 V 0.2 V 2.2 V 0.8 50 V pF 250 mA RECEIVER Receiver Differential Threshold High www.maximintegrated.com VTH_H -15V ≤ VCM ≤ +15V VIN = +12V VIN = -7V +1350 -1100 50 μA pF -15 +15 V +50 +200 mV Maxim Integrated │ 3 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Electrical Characteristics (continued) (VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2)) PARAMETER SYMBOL CONDITIONS Receiver Differential Threshold Low VTH_L -15V ≤ VCM ≤ +15V Receiver Input Hysteresis ΔVTH VCM = 0V, time from last transition is less than tD_FS Differential Input Fail-Safe Level VTH_FS MIN TYP -200 -15V ≤ VCM ≤ +15V MAX UNITS -50 mV 250 -50 mV +50 mV LOGIC INTERFACE (RE, RO, DE, DI) MAX22500E 2/3xVL MAX22501E 2/3 x VCC Input Voltage High VIH DE, DI, RE Input Voltage Low VIL DE, DI, RE Input Current IIN DI and DE, RE (after first transition) V MAX22500E 1/3 x VL MAX22501E 1/3 x VCC V +2 μA 10 kΩ Input Impedance on First Transition RIN_FT RO Output High Voltage VOH RE = GND, (VA - VB) > 200mV, IOUT = -1mA RO Output Low Voltage VOL RE = GND, (VA – VB) < -200mV, IOUT = +1mA Three-State Output Current at Receiver IOZR RE= high, 0 ≤ VRO ≤ VCC Thermal Shutdown Threshold TSH Temperature rising Thermal Shutdown Hysteresis TSH_HYS -2 DE, RE MAX22500E VL – 0.4 MAX22501E VCC - 0.4 V -1 0.4 V +1 μA PROTECTION ESD Protection (A and B Pins) ESD Protection (All Other Pins) www.maximintegrated.com +160 °C 10 °C Human Body Model ±15 IEC61000-4-2 Air Gap Discharge to GND ±7 IEC61000-4-2 Contact Discharge to GND ±6 Human Body Model ±2 kV kV Maxim Integrated │ 4 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Electrical Characteristics - Switching (VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2)) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DRIVER (Note 5) Driver Propagation Delay Differential Driver Output Skew Driver Differential Output Rise and Fall Time Data Rate tDPLH RL = 54Ω, CL = 50pF, Figures 3, 4 20 tDPHL RL = 54Ω, CL = 50pF, Figures 3, 4 20 tDSKEW tHL, tLH |tDPLH – tDPHL|, RL = 54Ω, CL= 50pF, Figures 3, 4 (Note 6) MAX22501E 1.2 MAX22500E, VL = VCC, VCC ≥ 3V 1.2 MAX22500E, VL ≠ VCC 1.6 RL = 54Ω, CL = 50pF, Figure 4 (Note 6) DR ns ns 3 ns 100 Mbps Driver Enable to Output High tDZH RL = 500Ω, CL = 50pF, Figures 5, 6 30 ns Driver Enable to Output Low tDZL RL = 500Ω, CL = 50pF, Figures 5, 6 30 ns Driver Disable Time from Low tDLZ RL = 500Ω, CL = 50pF, Figures 5, 6 30 ns Driver Disable Time from High tDHZ RL = 500Ω, CL = 50pF, Figures 5, 6 30 ns Driver Enable from Shutdown to Output High tDZH(SHDN) RL = 1kΩ, CL = 15pF, Figures 5, 6 100 µs Driver Enable from Shutdown to Output Low tDZL(SHDN) RL = 1kΩ, CL = 15pF, Figures 5, 6 100 µs 800 ns Time to Shutdown Driver Preemphasis Interval tSHDN tPRE (Notes 7, 8) 50 MAX22500E only, RPSET = 4kΩ 4.5V ≤ VCC ≤ 5.5V, RL = 100Ω, Figure 2 RPSET = 400kΩ 10 13 16 ns 0.8 1 1.2 μs RECEIVER (Note 5) Delay to Fail-Safe Operation Receiver Propagation Delay Receiver Output Skew Data Rate tD_FS 10 tRPLH,tRPHL CL = 15pF, Figure 7, Figure 8 tRSKEW |tRPHL - tRPLH|, CL= 15pF, Figures 7, 8 (Note 6) DR µs 20 ns 2.5 ns 100 Mbps Receiver Enable to Output High tRZH RL = 1kΩ, CL = 15pF, Figure 9 30 ns Receiver Enable to Output Low tRZL RL = 1kΩ, CL = 15pF, Figure 9 30 ns Receiver Disable Time from Low tRLZ RL = 1kΩ, CL = 15pF, Figure 9 30 ns Receiver Disable Time from High tRHZ RL = 1kΩ, CL = 15pF, Figure 9 30 ns www.maximintegrated.com Maxim Integrated │ 5 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Electrical Characteristics - Switching (continued) (VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2)) PARAMETER SYMBOL Receiver Enable from Shutdown to Output High tRZH(SHDN) Receiver Enable from Shutdown to Output Low tRZL(SHDN) Time to Shutdown tSHDN CONDITIONS MIN MAX UNITS RL=1kΩ, CL=15pF, Figure 9 100 μs RL=1kΩ, CL=15pF, Figure 9 100 μs 800 ns (Notes 7, 8) TYP 50 Note 1: All devices are 100% production tested at TA = +25°C. Specifications for all temperature limits are guaranteed by design. Note 2: 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 3: VODP is the differential voltage between A and B during the preemphasis interval on the MAX22500E, and is the differential voltage when preemphasis is disabled. VODP = DPRE x VOD. Note 4: ΔVOD and ΔVOC 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: Not production tested. Guaranteed by design. 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: 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. Test Circuits/Diagrams A VOD VODP B RL 2 RL 2 VOC Figure 1: Driver DC Test Load A OR B VOD B OR A VODP 50% tPRE MAX22500E only, preemphasis enabled VODP = DPRE x VOD Figure 2: Driver Preemphasis Timing www.maximintegrated.com Maxim Integrated │ 6 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables VCC DE A VOD VODP B RL CL Figure 3: Driver Timing Test Circuit f = 1MHz, tLH = 3ns, tHL = 3ns DI 50% VL OR VCC 50% 0 tDPLH tDPHL B A VOD VOD = (VA - VB) VO 90% 90% 0 VOD 10% 10% -VO tHL tLH tDSKEW = |tDPLH - tDPHL| Figure 4: Driver Propagation Delays GND OR VCC DI A B CL RL OUT DE 50% tDZH, tDZH(SHDN) 0.25V GENERATOR 50Ω OUT 50% tDHZ VL OR VCC 0V VOH 0V Figure 5: Driver Enable and Disable Times (tDZH, tDHZ) www.maximintegrated.com Maxim Integrated │ 7 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables V CC RL GND OR V CC DI A B DE 50% tDZL, tDZL(SHDN) VL OR VCC 50Ω GENERATOR VL OR VCC OUT CL 0V tDLZ 50% OUT 0.25V V OL Figure 6: Driver Enable and Disable Times (tDZL, tDLZ) A ATE R VID B Figure 7: Receiver Propagation Delay Test Circuit A +1V B RO -1V tRPLH tRPHL 50% VOH 50% tRSKEW = |tRPHL – tRPHL| VOL Figure 8: Receiver Propagation Delays www.maximintegrated.com Maxim Integrated │ 8 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables S3 +1.5V -1.5V R V IO RO RL 1kΩ S1 CL 15pF VL OR VCC S2 50Ω GENERATOR VL OR VCC VL OR VCC RE RE 50% tRZH, tRZH(SHDN) 0V V OH tRZL, tRZL(SHDN) S1 OPEN S2 CLOSED S3 = +1.5V 50% RO 50% V OH RO V OL VL OR VCC VL OR VCC 50% tRHZ RE 0V V OH RO 0.25V S1 OPEN S2 CLOSED S3 = +1.5V 50% 0V tRLZ S1 CLOSED S2 OPEN S3 = -1.5V VL OR VCC RO 0V S1 CLOSED S2 OPEN S3 = -1.5V 50% 0V RE 0V 0.25V V OL Figure 9: Receiver Enable and Disable Times www.maximintegrated.com Maxim Integrated │ 9 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Typical Operating Characteristics VCC = 5V, VL = VCC (MAX22500E only), 60Ω termination between A and B, TA = 25°C, unless otherwise noted. MAX22500E SUPPLY CURRENT vs. DATA RATE (PREEMPHASIS DISABLED) MAX22500E SUPPLY CURRENT vs. DATA RATE (PREEMPHASIS ENABLED) toc01 125 ICC (mA) ICC (mA) 54Ω LOAD 75 125 100 VCC = 5V, 54Ω LOAD 75 VCC = 3.3V, 54Ω LOAD 50 50 25 SQUARE WAVE ON DI (50% DUTY CYCLE) 125 100 VCC = 5V, 54Ω LOAD 100 VCC = 5V, NO LOAD 25 VCC = 3.3V, NO LOAD 0 0 0.1 VCC = 3.3V, 54Ω LOAD 75 50 VCC = 5V, NO LOAD VCC = 3.3V, NO LOAD 25 NO LOAD toc03 150 SQUARE WAVE ON DI (50% DUTY CYCLE) SQUARE WAVE ON DI (50% DUTY CYCLE) PSET RESISTOR ADJUSTED FOR EACH DATA RATE ICC (mA) 150 MAX22501E SUPPLY CURRENT vs. DATA RATE toc02 150 1 10 0.01 100 0.1 1 10 RO OUTPUT VOLTAGE LOW vs. LOAD CURRENT 0.1 1 10 DATA RATE (Mbps) 100 toc05 5.5 (VA - VB) > +200mV (VA - VB) < -200mV 5.0 0.40 0.35 VCC = 3.3V 4.5 0.30 VOH (V) VOL (V) 0.01 RO OUTPUT VOLTAGE HIGH vs. LOAD CURRENT toc04 0.50 0.45 0 100 DATA RATE (Mbps) DATA RATE (Mbps) 0.25 VCC = 5V 4.0 0.20 VCC = 3.3V 3.5 VCC = 5V 0.15 0.10 3.0 0.05 0.00 2.5 0 10 20 30 40 50 0 -10 SINK CURRENT (mA) DIFFERENTIAL DRIVER OUTPUT VOLTAGE vs. LOAD CURRENT -50 toc07 VCC = 5V 4.0 3.5 3.0 4 VCC = 3.3V 3 VOD (V) VOD (V) -40 4.5 VCC = 5V 5 -30 DIFFERENTIAL DRIVER OUTPUT VOLTAGE vs. TEMPERATURE toc06 6 -20 SOURCE CURRENT (mA) VCC = 3.3V 2.5 2.0 1.5 2 1.0 1 0.5 RL = 54Ω 0.0 0 0 25 50 75 LOAD CURRENT (mA) www.maximintegrated.com 100 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (ºC) Maxim Integrated │ 10 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Typical Operating Characteristics (continued) VCC = 5V, VL = VCC (MAX22500E only), 60Ω termination between A and B, TA = 25°C, unless otherwise noted. DRIVER OUTPUT VOLTAGE HIGH vs. LOAD CURRENT DRIVER OUTPUT VOLTAGE LOW vs. LOAD CURRENT toc08 1.0 DI = VCC 4.5 0.8 0.7 DRIVER OUTPUT VOLTAGE HIGH (V) DRIVER OUTPUT VOLTAGE LOW (V) toc09 5.0 DI = GND 0.9 VCC = 3.3V 0.6 0.5 0.4 VCC = 5V 0.3 0.2 0.1 0.0 0 25 50 75 100 125 4.0 VCC = 5V 3.5 VCC = 3.3V 3.0 2.5 2.0 150 0 -25 -50 -75 -100 -125 SOURCE CURRENT (mA) SINK CURRENT (mA) DRIVER PROPAGATION DELAY vs. TEMPERATURE 20 DRIVER PROPAGATION DELAY SKEW vs. TEMPERATURE toc10 4.5 16 14 toc11 5.0 RL = 54Ω CL = 50pF RL = 54Ω CL = 50pF 4.0 VCC = 3.3V, tDPHL VCC = 3.3V, tDPLH 3.5 tDSKEW (ns) DRIVER PROPAGATION DELAY (ns) 18 12 10 3.0 2.5 8 2.0 6 1.5 4 VCC = 3.3V 1.0 2 VCC = 5V, tDPHL VCC = 5V, tDPLH 0.5 0 VCC = 5V 0.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 TEMPERATURE (ºC) 20 35 50 65 80 95 110 125 TEMPERATURE (ºC) DRIVER PREMPHASIS (MAX22500E) RECEIVER PROPAGATION DELAY vs. TEMPERATURE toc13 toc12 20 VCC = 3.3V, tRPHL 18 RECEIVER PROPAGATION DELAY (ns) -150 VCC = 3.3V, tRPLH 16 DI 5V/div 14 12 VCC = 5V, tRPHL 10 8 VA-VB 2V/div VCC = 5V, tRPLH 6 4 2 0 RL = 54Ω, CL = 10pF, RSET = 8kΩ CL = 15pF -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (ºC) www.maximintegrated.com 0 1 0 1 1 0 20ns/div 1 0 0 1 Maxim Integrated │ 11 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Pin Configuration TOP VIEW TOP VIEW VCC B A 10 9 8 GND PSET 7 VCC B A GND 8 7 6 5 6 MAX22500E MAX22501E EP + + 1 2 3 4 5 1 2 3 4 VL RO DE RE DI RO RE DE DI TDFN-EP 3mm x 3mm TDFN-EP 3mm x 3mm Pin Description PIN NAME FUNCTION - VL Logic Supply Input. VL defines the interface logic levels on DE, DI and RO. Apply a voltage between 1.6V to 5.5V to VL. Bypass VL to ground with a 0.1μF capacitor as close to the device as possible. 2 1 RO Receiver Output. See the Receiving Function Table for more information. 3 3 DE Driver Output Enable. Force DE high to enable driver. Pull DE low to three-state the driver output. 4 2 RE Receiver Enable. Pull RE high to disable and the receiver and tri-state RO. The device is in low-power shutdown when RE = high and DE = low. 5 4 DI Driver Input. See the Transmitting Function Table for more information. MAX22500E MAX22501E 1 6 - PSET Preemphasis Select Control Input. Connect a resistor from PSET to GND to select the preemphasis duration. See the Layout Recommendations in the Applications Information section for more information. To disable preemphasis, connect PSET to GND or VCC. 7 5 GND Ground 8 6 A Noninverting Receiver Input/Driver Output 9 7 B Inverting Receiver Input/Driver Output 10 8 VCC www.maximintegrated.com Supply Input. Bypass VCC to ground with a 0.1μF ceramic capacitor as close to the device as possible. Maxim Integrated │ 12 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Functional Tables Transmitting Function Table INPUTS OUTPUTS RE DE DI A B X 1 1 1 0 X 1 0 0 1 0 0 X High Impedance 1 0 X High Impedance Shutdown. A and B are high impedance X = Don’t care Receiving Function Table INPUTS OUTPUTS RE DE (VA - VB) Time from Last A-B Transition 0 X ≥ +200mV Always 1 RO 0 X -200mV < (VA - VB) < +200mV < tD_FS Indeterminate RO is latched to previous value 0 X -50mV < (VA - VB) < +50mV > tD_FS 1 0 X ≤ -200mV Always 0 0 X Open/Shorted > tD_FS 1 1 1 X X High Impedance 1 0 X X Shutdown. RO is high impedance Functional Diagrams Half-Duplex Application Circuit 5V 3.3V RE RE RO RO R B DE DI A D PSET www.maximintegrated.com VCC VCC 120Ω MICROCONTROLLER MICROCONTROLLER VL 3.3V 3.3V R B DE DI A 120Ω D MAX22500E MAX22501E GND GND Maxim Integrated │ 13 MAX22500E/MAX22501E Detailed Description The MAX22500E/MAX22501E ESD-protected RS-485/ RS-422 transceivers are optimized for high-speed, halfduplex communications over long cables. Both transceivers feature integrated hot-swap functionality to eliminate false transitions on the driver during power-up or during a hotplug event. These transceivers also feature fail-safe receiver inputs, guaranteeing a logic-high on the receiver output when inputs are shorted or open for longer than 10µs (typ). Receiver Threshold Voltages The MAX22500E and MAX22501E receivers feature large threshold hysteresis of 250mV (typ) for increased differential noise rejection. Additionally, the receivers feature symmetrical threshold voltages. Symmetric thresholds have the advantage that recovered data at the RO output does not have duty cycle distortion. Typically, fail-safe receivers, which have unipolar (non-symmetric) thresholds, show some duty cycle distortion at high signal attenuation due to long cable lengths. Preemphasis (MAX22500E only) The MAX22500E features integrated driver preemphasis circuitry, which strongly improves signal integrity at high data rates over long distances by reducing inter-symbol interference (ISI) caused by long cables. Preemphasis is set by connecting a resistor (RPSET) between PSET and ground. Long cables attenuate the high-frequency content of transmitted signals due to the cable's limited bandwidth. This causes signal/pulse distortion at the receiving end, resulting in ISI. ISI causes jitter in data and clock recovery circuits. ISI can be visualized by considering the following cases: If a series of ones (1's) is transmitted, followed by a zero (0), the transmission-line voltage has risen to a high value by the end of the string of ones. It takes longer for the signal to move toward the '0' state because the starting voltage on the line is so far from the zero crossing. Similarly, if a data pattern has a string of zeros followed by a one and then another zero, the one-to-zero transition starts from a voltage that is much closer to the zero-crossing (VA - VB = 0) and it takes much less time for the signal to reach the zero crossing. Preemphasis reduces ISI by boosting the differential signal amplitude at every transition edge, counteracting the high frequency attenuation of the cable. When the DI input changes from a logic-low to a logic-high, the differential output (VA - VB) is driven high to VODP. At the end of the preemphasis interval, the differential voltage returns to a lower level (VOD). The preemphasis differential high voltage (VODP) is typically 1.37 the VOD voltage. www.maximintegrated.com 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables If DI switches back to a logic-low state before the preemphasis interval ends, the differential output switches directly from the 'strong' VODP high to a 'strong' low (-VODP). Driver behavior is similar when the DI input changes from a logic-high to a logic-low. When this occurs, the differential output is pulled low to -VODP until the end of the preemphasis interval, at which point VA - VB = -VODP. Setting the Preemphasis Interval Connect a resistor (RPSET) between PSET and GND to set the preemphasis time interval on the MAX22500E. An optimum preemphasis interval ranges from 1 to 1.5 unit intervals (bit time). Use the following equation to calculate the resistance needed on PSET to achieve a 1.2 preemphasis interval: RPSET = 400x109/DR where DR is the data rate and 1Mbps ≤ DR ≤ 100Mbps. Preemphasis only minimally degrades the jitter on the eye diagram when using short cables, making it reasonable to permanently enable preemphasis on systems where cable lengths may vary or change. Figure 10 and Figure 11 are eye diagrams taken at 100Mbps over a 10m Cat-5e cable. Note that the eye varies only slightly as preemphasis is enabled or disabled. Figure 12 and Figure 13 show the driver eye diagrams over a long cable length. The MAX22500E was used as the driver and the eye diagrams were taken at the receiver input after a length of 100m Cat-5e cable. Figure 12 shows the signal at the receiver when the driver preemphasis is disabled. Figure 13 shows the receiver signal when preemphasis is enabled. Fail-Safe Functionality The MAX22500E/MAX22501E feature fail-safe receiver inputs, guaranteeing a logic-high on the receiver output (RO) when the receiver inputs are shorted or open for longer than 10μs (typ). When the differential receiver input voltage is greater than -50mV [(VA - VB) ≥ -50mV] for more than 10μs (typ), RO is logic-high. For example, in the case of a terminated bus with all transmitters disabled, the receiver’s differential input voltage is pulled to 0V by the termination resistor, so (VA - VB = 0V) > -50mV and RO is guaranteed to be a logic-high after 10μs (typ). Driver Single-Ended Operation The A and B outputs on the MAX22500E/MAX22501E can be used in the standard differential operating mode or as single-ended outputs. Because the driver outputs swing rail-to-rail, they can also be used as individual standard TTL logic outputs. Maxim Integrated │ 14 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables EYE DIAGRAM PREEMPHASIS DISABLED EYE DIAGRAM PREEMPHASIS ENABLED VA - VB 1V/div VA - VB 1V/div 100Mbps, 10m Cat-5e Cable 2.5ns/div Preemphasis Enabled 100Mbps, 10m Cat-5e Cable 2.5ns/div Preemphasis Disabled Figure 10: Eye Diagram, 100Mbps Over 10m Cat-5e Cable, Preemphasis Disabled Figure 11: Eye Diagram, 100Mbps Over 10m Cat-5e Cable, Preemphasis Enabled EYE DIAGRAM PREEMPHASIS ENABLED EYE DIAGRAM PREEMPHASIS DISABLED VA - VB 700mV/div VA - VB 700mV/div 50Mbps, 100m Cat-5e Cable 5ns/div Preemphasis Disabled Figure 12: Eye Diagram, 50Mbps Over 100m Cat-5e Cable, Preemphasis Disabled www.maximintegrated.com 50Mbps, 100m Cat-5e Cable 5ns/div Preemphasis Enabled Figure 13: Eye Diagram, 50Mbps Over 100m Cat-5e Cable, Preemphasis Enabled Maxim Integrated │ 15 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Hot-Swap Capability is not needed. Pull the RE input high and the DE input low to put the device in low-power shutdown mode. If the inputs are in this state for at least 800ns, the parts are guaranteed to enter shutdown. The MAX22500E/ MAX22501E draw 5μA (max) of supply current when the device is in shutdown. The DE and RE enable inputs feature hot-swap functionality. At each input there are two NMOS devices, M1 and M2 (Figure 14). When VCC ramps from zero, an internal 10ms timer turns on M2 and sets the SR latch, which also turns on M1. Transistors M2 (a 500μA current sink) and M1 (a 100μA current sink) pull DE to GND through a 5kΩ 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 10μs, 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. The RE and DE inputs can be driven simultaneously. The MAX22500E/MAX22501E are guaranteed not to enter shutdown if RE is high and DE is low for less than 50ns. Applications Information Layout Recommendations Ensure that the preemphasis set resistor (RPSET) is located close to the PSET and GND pins in order to minimize interference by other signals. Minimize the trace length to the PSET resistor. Additionally, place a ground plane under RPSET and surround it with ground connections/ traces to minimize interference from the A and B switching signals. See Figure 15. There is a complimentary circuit for RE that uses two PMOS devices to pull RE to VCC. Driver Output Protection Network Topology Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. The first, a current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range. The second, a thermal-shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature exceeds +160°C (typ). The MAX22500E/MAX22501E transceivers are designed for high-speed bidirectional RS-485/RS-422 data communications. Multidrop networks can cause impedance discontinuities which affect signal integrity. Maxim recommends using a point-to-point network topology (Figure 16), instead of a multidrop topology, when communicating with high data rates. Terminate the transmission line at both ends with the cable’s characteristic impedance to reduce reflections. Low-Power Shutdown Mode The MAX22500E/MAX22501E feature a low-power shutdown mode to reduce supply current when the transceiver VCC 10µs TIMER TIMER 5kΩ DE (HOT-SWAP) DE 100µA 500µA Figure 14: Simplified Structure of the Driver Enable (DE) Pin www.maximintegrated.com Maxim Integrated │ 16 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Figure 15. Sample PSET Resistor Placement 3.3V 5V 5V 0.1µF 0.1µF VL VCC VCC RE MICROCONTROLLER RE RO R DE DI B B A A RO R DE D D DI PSET PSET MAX22500E GND MAX22500E GND Figure 16: Point-to-Point Half-Duplex Communication for High Speeds www.maximintegrated.com Maxim Integrated │ 17 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Ordering Information PREEMPHASIS LOGIC SUPPLY PIN-PACKAGE PIN-PITCH PACKAGE CODE MAX22500EATB+ Y Y TDFN10-EP* 5mm T1033+2 MAX22500EATB+T Y Y TDFN10-EP* 5mm T1033+2 MAX22501EATA+ N N TDFN8-EP* 6.5mm T833+2 MAX22501EATA+T N N TDFN8-EP* 6.5mm T833+2 PART + Denotes a lead (Pb)-free/RoHS-compliant package. * EP = Exposed Pad www.maximintegrated.com Maxim Integrated │ 18 MAX22500E/MAX22501E 100Mbps Half-Duplex RS-485/RS-422 Transceivers for Long Cables Revision History REVISION NUMBER REVISION DATE 0 6/17 DESCRIPTION Initial release PAGES CHANGED — 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. © 2017 Maxim Integrated Products, Inc. │ 19