20Mbps, +3.3V, SOT23 RS-485/ RS-422 Transmitters MAX3293/MAX3294/MAX3295. Features

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1 19-277; Rev 3; 3/11 2Mbps, +3.3V, SOT23 RS-485/ General Description The low-power, highspeed tramitters for RS-485/RS-422 communication operate from a single +3.3V power supply. These devices contain one differential tramitter. The MAX3295 tramitter operates at data rates up to 2Mbps, with an output skew of less than 5, and a guaranteed driver propagation delay below 25. The MAX3293 (25kbps) and MAX3294 (2.5Mbps) are slew-rate limited to minimize EMI and reduce reflectio caused by improperly terminated cables. The output level is guaranteed at +1.5V with a standard 54Ω load, compliant with RS-485 specificatio. The tramitter draws 5mA of supply current when unloaded, and 1µA in lowpower shutdown mode ( = GND). Hot-swap circuitry eliminates false traitio on the data cable during circuit initialization or connection to a live backplane, and short-circuit current limiting and thermalshutdown circuitry protect the driver agait excessive power dissipation. The are offered in a 6-pin SOT23 package, and are specified over the automotive temperature range. RS-485/RS-422 Communicatio Clock Distribution Telecom Equipment Automotive Security Equipment Point-of-Sale Equipment Industrial Control Applicatio Typical Operating Circuit Features Space-Saving 6-Pin SOT23 Package 25kbps/2.5Mbps/2Mbps Data Rates Available Operate from a Single +3.3V Supply ESD Protection ±9kV Human Body Model Slew-Rate Limited for Errorless Data Tramission (MAX3293/MAX3294) 1µA Low-Current Shutdown Mode -7V to +12V Common-Mode Input Voltage Range Current Limiting and Thermal Shutdown for Driver-Overload Protection Hot-Swap Inputs for Telecom Applicatio Automotive Temperature Range (-4 C to +125 C) Ordering Information PART TEMP RANGE PIN-PACKAGE MAX3293AUT+T -4 C to +125 C 6 SOT23-6 MAX3294AUT+T -4 C to +125 C 6 SOT23-6 MAX3295AUT+T -4 C to +125 C 6 SOT23-6 +Denotes a lead(pb)-free/rohs-compliant package. T = Tape and reel. PART MAXIMUM DATA RATE (Mbps) Selector Guide SLEW- RATE LIMITED MAX3293AUT+T.25 es MAX3294AUT+T 2.5 es MAX3295AUT+T 2 No TOP MARK ABNI or ABVH ABNJ or ABVI ABNK or ABVJ 12Ω DI D R RO Pin Configuration appears at end of data sheet. MAX3293 MAX3294 MAX3295 MAX328E MAX3281E MAX3283E MAX3284E Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND, unless otherwise noted.) Supply Voltage ( )...+6V, DI...-.3V to +6V,...-7V to +12.5V Maximum Continuous Power Dissipation (T A = +7 C) SOT23 (derate 8.2mW/ C above +7 C) mW 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 conditio beyond those indicated in the operational sectio of the specificatio is not implied. Exposure to absolute maximum rating conditio for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS Operating Temperature Ranges MAX32 AUT...-4 C to +125 C Storage Temperature Range C to +16 C Junction Temperature C Lead Temperature (soldering, 1s)...+3 C Soldering Temperature (reflow) C ( = +3.3V ±5%, T A = T MIN to T MAX, unless otherwise noted. Typical values are at = +3.3V and T A = +25 C.) (Notes 1, 2) POWER SUPPL PARAMETER SMBOL CONDITIONS MIN TP MAX UNITS Supply Voltage V Supply Current in Normal Operation I Q No load, DI = or GND, = 5 ma Supply Current in Shutdown Mode I SHDN No load, = GND 1 1 µa DRIVER Differential Driver Output V OD Figure 1, =, DI = GND or Change in Magnitude of Differential Output Voltage Driver Common-Mode Output Voltage Change in Magnitude of Common- Mode Voltage DRIVER LOGIC ΔV OD Figure 1, R = 27Ω or 5Ω, = (Note 3) V OC Figure 1, R = 27Ω or 5Ω, =, DI = or GND R = 5Ω (RS-422), T A +85 C R = 27Ω (RS-485), T A +85 C V.2 V V ΔV OC Figure 1, R = 27Ω or 5Ω (Note 3).2 V Input High Voltage V IH, DI 2. V Input Low Voltage V IL, DI.8 V Input Current I IN, DI µa Output Leakage I O = GND, = GND or, V IN = +12V V V IN = -7V µa Driver Short-Circuit Foldback Output Current Driver Short-Circuit Output Current ( - 1V) V OUT +12V, output high +25 I OSFD -7V V OUT 1V, output high -25 V OUT +12V, output low -25 I OSD -7V V OUT, output high +25 Thermal-Shutdown Threshold T TS 16 C Thermal-Shutdown Hysteresis T TSH 4 C ESD Protection, Human Body Model ±9 kv 2 ma ma

3 SWITCHING CHARACTERISTICS (MAX3293) ( = +3.3V ±5%, T A = +25 C, unless otherwise noted. Typical values are at = +3.3V.) PARAMETER SMBOL CONDITIONS MIN TP MAX UNITS Driver Propagation Delay SWITCHING CHARACTERISTICS (MAX3294) t PLH Figures 2, 3; R DIFF = 54, 4 13 t PHL C L = 5pF 4 13 Driver Differential Output Rise t R Figures 2, 3; R DIFF = 54, 4 12 or Fall Time t F C L = 5pF 4 12 Driver-Output Skew t SKEW Figures 2, 3; R DIFF = 54, C L = 5pF, t SKEW = t PLH - t PHL (Note 5) ( = +3.3V ±5%, T A = +25 C, unless otherwise noted. Typical values are at = +3.3V.) Differential Driver-Output Skew t DSKEW Figures 2, 3; R DIFF = 54, C L = 5pF Maximum Data Rate Figures 2, 3; R DIFF = 54, C L = 5pF 25 kbps Driver Enable to Output High t H Figures 4, 5; S2 closed, R L = 5, Driver Enable to Output Low t L Figures 4, 5; S1 closed, R L = 5, Driver Disable Time from Low t L Figures 4, 5; S1 closed, R L = 5, Driver Disable Time from High t H Figures 4, 5; S2 closed, R L = 5, Device-to-Device Propagation Delay Matching Same power supply, maximum temperature difference between devices = +3 C (Note 5) PARAMETER SMBOL CONDITIONS MIN TP MAX UNITS Driver Propagation Delay t PLH Figures 2, 3; R DIFF = 54, 24 7 t PHL C L = 5pF 24 7 Driver Differential Output Rise t R Figures 2, 3; R DIFF = 54, 1 7 or Fall Time t F C L = 5pF 1 7 Driver-Output Skew t SKEW Figures 2, 3; R DIFF = 54, C L = 5pF, t SKEW = t PLH - t PHL (Note 5) Differential Driver-Output Skew t DSKEW Figures 2, 3; R DIFF = 54, C L = 5pF Maximum Data Rate Figures 2, 3; R DIFF = 54, C L = 5pF 2.5 Mbps Driver Enable to Output High t H Figures 4, 5; S2 closed, R L = 5, 4 Driver Enable to Output Low t L Figures 4, 5; S1 closed, R L = 5, Driver Disable Time from Low t L Figures 4, 5; S1 closed, R L = 5, Driver Disable Time from High t H Figures 4, 5; S2 closed, R L = 5, Device-to-Device Propagation Delay Matching Same power supply, maximum temperature difference between devices = +3 C (Note 5) 46 3

4 SWITCHING CHARACTERISTICS (MAX3295) ( = +3.3V ±5%, T A = +25 C, unless otherwise noted. Typical values are at = +3.3V.) PARAMETER SMBOL CONDITIONS MIN TP MAX UNITS Driver Propagation Delay Driver Differential Output Rise or Fall Time t PLH 25 Figures 2, 3; R DIFF = 54, C L = 5pF t PHL 25 t T A = -4 C to +125 C 18.5 R Figures 2, 3; R T A < +85 C 15 DIFF = 54, T A = -4 C to +125 C 18.5 t F C L = 5pF T A < +85 C 15 Driver-Output Skew t SKEW Figures 2, 3; R DIFF = 54, C L = 5pF, t SKEW = t PLH - t PHL Note 1: Devices production tested at +25 C. Limits over the operating temperature range 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: ΔV OD and ΔV OC are the changes in V OD and V OC, respectively, when the DI input changes state. Note 4: The maximum current applies to peak current just prior to foldback current limiting. Note 5: Guaranteed by design; not production tested. 5 Differential Driver-Output Skew t DSKEW Figures 2, 3; R DIFF = 54, C L = 5pF 5 Maximum Data Rate Figures 2, 3; R DIFF = 54, C L = 5pF, T A +85 C 2 Figures 2, 3; R DIFF = 54, C L = 5pF 16 Driver Enable to Output High t H Figures 4, 5; S2 closed, R L = 5, Driver Enable to Output Low t L Figures 4, 5; S1 closed, R L = 5, Driver Disable Time from Low t L Figures 4, 5; S1 closed, R L = 5, Driver Disable Time from High t H Figures 4, 5; S2 closed, R L = 5, Device-to-Device Propagation Delay Matching Same power supply, maximum temperature difference between devices = +3 C (Note 5) Mbps

5 V OD Figure 1. Driver DC Test Load 3V DI V ID R R R DIFF V OC C L C L Test Circuits and Timing Diagrams OUTPUT UNR TEST Figure 4. Enable/Disable Timing Test Load 3V, V OL, C L R L S1 S2 1.5V 1.5V 2.3V OUTPUT NORMALL LOW 2.3V t L(SHDN), t L t L OUTPUT NORMALL HIGH V OL +.25V V OH -.25V t H(SHDN), t H t H Figure 2. Driver Timing Test Circuit Figure 5. Driver Enable and Disable Times 3V DI 1.5V f = 1MHz, t R 3, t F 3 t PLH t PHL 1.5V 1/2 V O V O 1/2 V O V DIFF = V () - V () V DIFF V O -V O 1% 9% 9% 1% t R t F t SKEW = t PLH - t PHL Figure 3. Driver Propagation Delays 5

6 ( = +3.3V, T A = +25 C, unless otherwise noted.) SUPPL CURRENT (ma) OUTPUT CURRENT (ma) MAX3295 SUPPL CURRENT vs. DATA RATE = NO LOAD T A = +125 C T A = +85 C T A = -4 C T A = +25 C DATA RATE (Mbps) OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE MAX toc1 MAX toc4 SUPPL CURRENT (ma) DIFFERENTIAL OUTPUT VOLTAGE (V) SUPPL CURRENT vs. TEMPERATURE = NO LOAD NO SWITCHING TEMPERATURE ( C) DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE R DIFF = 1Ω R DIFF = 54Ω Typical Operating Characteristics MAX toc2 MAX toc5 SUPPL CURRENT (μa) OUTPUT CURRENT (ma) SHUTDOWN SUPPL CURRENT vs. TEMPERATURE = GND TEMPERATURE ( C) DRIVER-OUTPUT CURRENT vs. DRIVER-OUTPUT LOW VOLTAGE MAX toc3 MAX toc DIFFERENTIAL OUTPUT VOLTAGE (V) TEMPERATURE ( C) OUTPUT LOW VOLTAGE (V) OUTPUT CURRENT (ma) DRIVER-OUTPUT CURRENT vs. DRIVER-OUTPUT HIGH VOLTAGE MAX toc7 OUTPUT SKEW () OUTPUT SKEW vs. TEMPERATURE MAX toc8 PROPAGATION LA () DRIVER PROPAGATION LA vs. TEMPERATURE R DIFF = 54Ω C L = 5pF t PHL t PLH MAX toc OUTPUT HIGH VOLTAGE (V) TEMPERATURE ( C) TEMPERATURE ( C) 6

7 Typical Operating Characteristics (continued) ( = +3.3V, T A = +25 C, unless otherwise noted.) DI,, : 1V/div DI: 2V/div DRIVER PROPAGATION LA 2/div, MAX toc1 -,, : 2V/div LOAD DRIVER-OUTPUT WAVEFORM (f IN = 16Mbps) MAX toc13 ENABLE RESPONSE TIME MAX toc11 4/div,,, : 1V/div EE DIAGRAM (f IN = 2Mbps) UNLOAD DRIVER-OUTPUT WAVEFORM (f IN = 16Mbps) 2/div MAX toc14 MAX toc12, : 5mV/div 2/div, : 5mV/div 1/div PIN NAME FUNCTION Pin Description 1 DI Driver Input. A logic low on DI forces the noninverting output () low and the inverting output () high. A logic high on DI forces the noninverting output () high and the inverting output () low. 2 Positive Supply. = +3.3V ±5%. Bypass to GND with a.1µf capacitor. 3 Driver Output Enable. Force high to enable driver. Pull low to disable the driver. Hot-swap input, see the Hot-Swap Capability section. 4 Inverting RS-485/RS-422 Output 5 GND Ground 6 Noninverting RS-485/RS-422 Output 7

8 Detailed Description The are low-power tramitters for RS-485/RS-422 communication. The MAX3295 operates at data rates up to 2Mbps, the MAX3294 up to 2.5Mbps (slew-rate limited), and the MAX3293 up to 25kbps (slew-rate limited). These devices are enabled using an active-high driver enable () input. When disabled, outputs enter a high-impedance state, and the supply current reduces to 1µA. The have a hot-swap input structure that prevents disturbance on the differential signal lines when a circuit board is plugged into a hot backplane (see the Hot-Swap Capability section). Drivers are also short-circuit current limited and are protected agait excessive power dissipation by thermal-shutdown circuitry. Driver The driver accepts a single-ended, logic-level input (DI) and tralates it to a differential RS-485/RS-422 level output ( and ). Driving high enables the driver, while pulling low places the driver outputs ( and ) into a high-impedance state (see Table 1). Low-Power Shutdown Force low to disable the MAX3293/MAX3294/ MAX3295. In shutdown mode, the device coumes a maximum of 1µA of supply current. Hot-Swap Capability Hot-Swap Input When circuit boards are ierted into a hot or powered backplane, disturbances to the enable can lead to data errors. Upon initial circuit board iertion, the processor undergoes its power-up sequence. During this period, the output drivers are high impedance and are unable to drive the input of the MAX3293/ MAX3294/MAX3295 to a defined logic level. Leakage currents up to 1µA from the high-impedance output could cause to drift to an incorrect logic state. Additionally, parasitic circuit board capacitance could Table 1. MAX3293/MAX3294/ MAX3295 (RS-485/RS-422) Tramitting Function Table INPUTS OUTPUTS DI X Shutdown Shutdown X = Don t care. cause coupling of or GND to. These factors could improperly enable the driver. The eliminate all above issues with hot-swap circuitry. When rises, an internal pulldown circuit holds low for approximately 1µs. After the initial power-up sequence, the pulldown circuit becomes traparent, resetting the hot-swap tolerable input. EN TIMER 5.6kΩ TIMER M1 1μs 2mA 1μA M2 (HOT SWAP) Figure 6. Simplified Structure of the Driver Enable Input () - DIFFERENTIAL POWER-UP GLITCH (.1V/μs) 4μs/div Figure 7. Differential Power-Up Glitch (.1V/µs) 2V/div 1mV/div 1mV/div 2mV/div 8

9 Hot-Swap Input Circuitry The enable input features hot-swap capability. At the input, there are two NMOS devices, M1 and M2 (Figure 6). When ramps from zero, an internal 1µs timer tur on M2 and sets the SR latch, which also tur on M1. Traistors M2, a 2mA current sink, and M1, a 1µA current sink, pull to GND through a 5.6kΩ resistor. M2 is designed to pull to the disabled state agait an external parasitic capacitance up to 1pF that may drive high. After 1µs, the timer deactivates M2 while M1 remai on, holding low agait threestate leakages that can drive high. M1 remai on until an external source overcomes the required input current. At this time, the SR latch resets and M1 tur - DIFFERENTIAL POWER-UP GLITCH (1V/μs) 1μs/div 2V/div 1mV/div 1mV/div 2mV/div off. When M1 tur off, reverts to a standard, highimpedance CMOS input. Whenever drops below 1V, the hot-swap input is reset. Hot-Swap Line Traient During a hot-swap event when the driver is connected to the line and is powered up, the driver must not cause the differential signal to drop below 2mV. Figures 7, 8, and 9 show the results of the MAX3295 during power-up for three different ramp rates (.1V/µs, 1V/µs, and 1/µs). The photos show the ramp, the singleended signal on each side of the 1Ω termination, as well as the differential signal across the termination. ESD Protection Human Body Model Figure 1 shows the Human Body Model, and Figure 11 shows the current waveform it generates when discharged into low impedance. This model coists of a 1pF capacitor charged to the ESD voltage of interest, which is then discharged into the device through a 1.5kΩ resistor. HIGH- VOLTAGE DC SOURCE R C 1MΩ CHARGE-CURRENT- LIMIT RESISTOR Cs 1pF R D 1.5kΩ DISCHARGE RESISTANCE STORAGE CAPACITOR VICE UNR TEST Figure 8. Differential Power-Up Glitch (1V/µs) DIFFERENTIAL POWER-UP GLITCH (1/μs) Figure 1. Human Body ESD Test 2V/div I P 1% 9% Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) - 2/div 5mV/div 5mV/div 1mV/div AMPERES 36.8% 1% t RL TIME t DL CURRENT WAVEFORM Figure 9. Differential Power-Up Glitch (1/µs) Figure 11. Current Waveform 9

10 Reduced EMI and Reflectio (MAX3293/MAX3294) The MAX3293/MAX3294 are slew-rate limited, minimizing EMI and reducing reflectio caused by improperly terminated cables. Figure 12 shows Fourier analysis of the MAX3295 tramitting a 125kHz signal. High-frequency harmonics with large amplitudes are evident. Figure 13 shows the same information, but for the slewrate-limited MAX3293, tramitting the same signal. The high-frequency harmonics have much lower amplitudes, and the potential for EMI is significantly reduced. To minimize reflectio, 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. The slew-rate-limited MAX3293 and MAX3294 are more tolerant of imperfect termination. DRIVER-OUTPUT WAVEFORM AND FFT PLOT OF MAX3295 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 agait 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 +16 C. PROCESS: BiCMOS DRIVER-OUTPUT WAVEFORM AND FFT PLOT OF MAX3293 Chip Information 1dB/div Figure 12. Driver-Output Waveform and FFT Plot of MAX3295 Tramitting a 125kHz Signal 1dB/div Figure 13. Driver-Output Waveform and FFT Plot of MAX3293 Tramitting a 125kHz Signal TOP VIEW DI Pin Configuration MAX3293 MAX3294 MAX GND Package Information For the latest package outline information and land patter (footprints), go to Note that a +, #, or - in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertai to the package regardless of RoHS status. PACKAGE TPE PACKAGE CO OUTLINE NO. LAND PATTERN NO SOT23 U6CN SOT23-6 1

11 REVISION NUMBER REVISION DATE SCRIPTION Revision History PAGES CHANGED 3 3/11 Added lead-free parts to the Ordering Information and Selector Guide tables 1 Maxim cannot assume respoibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licees are implied. Maxim reserves the right to change the circuitry and specificatio without notice at any time. Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.