MAX3471CUA

19-0497; Rev 0; 2/98 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems ____________________________Features ♦ 1.6µA Supply Current with Receiver Enabled This device features true fail-safe operation that guarantees a logic-high receiver output when the receiver inputs are open or shorted. This means that the receiver output will be a logic high if all transmitters on a terminated bus are disabled (high impedance). The MAX3471 has a 1/8-unit load input resistance. When driver outputs are enabled and pulled above VCC or below GND, internal circuitry prevents battery backcharging. The MAX3471 is available in an 8-pin µMAX package. ♦ 1/8-Unit-Load Receiver Input ________________________Applications ___________________Pin Configuration ♦ +2.5V to +5.5V Single-Supply Operation ♦ True Fail-Safe Receiver Input ♦ Available in µMAX Package ♦ -7V to +10V Common-Mode Input Voltage Range _______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX3471CUA 0°C to +70°C 8 µMAX MAX3471EUA -40°C to +85°C 8 µMAX Remote Meter Reading TOP VIEW Battery-Powered Differential Communications Level Translators RO 1 8 VCC RE 2 7 B DE 3 6 A DI 4 5 GND MAX3471 µMAX Typical Application Circuit VCC DI VCC VCC B B A A 0.1µF DE D D DE RO RE B R GND A B VCC GND DI DE RO RE DI R VCC RO RE GND R D REMOTE UNIT A R D DI CENTRAL UNIT DE RO RE MAX3471 REMOTE UNIT REMOTE UNIT TYPICAL HALF-DUPLEX RS-485 NETWORK ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX3471 ________________General Description The MAX3471 half-duplex transceiver is intended for lithium battery-powered RS-485/RS-422 applications. It draws only 1.6µA (typical) supply current from a 3.6V supply with the receiver enabled and the driver disabled. Its wide 2.5V to 5.5V supply voltage guarantees operation over the lifetime of a lithium battery. MAX3471 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (VCC) ..............................................................7V Control Input Voltage (RE, DE)...................-0.3V to (VCC + 0.3V) Driver Input Voltage (DI).............................-0.3V to (VCC + 0.3V) Driver Output/Receiver Input Voltage (A, B).....................±10.5V Receiver Output Voltage (RO)....................-0.3V to (VCC + 0.3V) Continuous Power Dissipation µMAX (derate 4.5mW/°C above +70°C) ......................362mW Operating Temperature Ranges MAX3471CUA .....................................................0°C to +70°C MAX3471EUA ..................................................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referred to device ground unless otherwise noted. 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 = +2.5V to +5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.6V and TA = +25°C.) (Note 1) PARAMETER SYMBOL Differential Driver Output (no load) VOD1 Differential Driver Output (with load) Change in Magnitude of Differential Output Voltage (Note 2) Driver Common-Mode Output Voltage Change in Magnitude of Common-Mode Voltage (Note 2) VOD2 CONDITIONS Figure 1 TYP R = 750Ω (RS-422) 1.5 3.28 R = 27Ω (RS-485) 0.2 0.83 R = 27Ω (RS-485), VCC = 5V, TA = +25°C ∆VOD Figure 1, R = 750Ω or 27Ω VOC Figure 1, R = 750Ω or 27Ω ∆VOC Figure 1, R = 750Ω or 27Ω Input High Voltage VIH DE, DI, RE Input Low Voltage VIL DE, DI, RE DI Input Hysteresis VHYS MAX UNITS VCC V V 1.5 0.2 0.6 x VCC 0.2 0.7 x VCC IIN1 DE, DI, RE IIN2 DE = GND, VCC = GND or 5.5V Driver Short-Circuit Output Current (Note 3) IOSD -7V ≤ VOUT ≤ 10V Receiver Differential Threshold Voltage VTH -7V ≤ VCM ≤ 10V V V ±0.001 ±1 0.105 VIN = -7V -0.075 VCC ≤ 3.6V -60 60 VCC ≤ 5.5V -130 130 -250 V mV VIN = 10V -450 V V 0.3 x VCC 100 Input Current (A and B), Half Duplex Input Current MIN Figure 1 (R = open) -50 µA mA mA mV Receiver Input Hysteresis ∆VTH VCM = 0 Receiver Output High Voltage VOH IO = -0.8mA, VID = -50mV Receiver Output Low Voltage VOL IO = 2.2mA, VID = -450mV 0.4 V Three-State Current at Receiver Output IOZR 0 ≤ VO ≤ VCC ±1 µA Receiver Input Resistance RIN -7V ≤ VCM ≤ 10V 2 32 mV VCC - 0.4 96 _______________________________________________________________________________________ V kΩ 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems (VCC = +2.5V to +5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.6V and TA = +25°C.) (Note 1) PARAMETER Receiver Output Short-Circuit Current Supply Current SYMBOL IOSR ICC CONDITIONS 0 ≤ VRO ≤ VCC VCC ≤ 3.6V, no load, RE = DI = GND or VCC, VA = VB = 0 VCC ≤ 5.5V, no load, RE = DI = GND or VCC, VA = VB = 0 MIN TYP MAX VCC ≤ 3.6V -20 50 VCC ≤ 5.5V -40 110 DE = VCC 50 60 DE = GND 1.6 2 DE = VCC 83 100 DE = GND 2.8 4 UNITS mA µA SWITCHING CHARACTERISTICS (VCC = +2.5V to +5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.6V and TA = +25°C.) TYP MAX UNITS Driver Input to Output Propagation Delay PARAMETER SYMBOL tDPLH, tDPHL Figures 3 and 5, RDIFF = 1.5kΩ, CL1 = CL2 = 100pF CONDITIONS MIN 1.40 2.00 µs Driver Output Skew (tDPLH - tDPHL) tDSKEW Figures 3 and 5, RDIFF = 1.5kΩ, CL1 = CL2 = 100pF 0.025 Driver Rise or Fall Time tDR, tDF Figures 3 and 5, RDIFF = 1.5kΩ, CL1 = CL2 = 100pF 0.75 µs 1.34 1.75 µs Driver Enable Time to Output High tDZH Figures 4 and 6, CL = 100pF, S2 closed, S1 open 1.5 6.00 µs Driver Enable Time to Output Low tDZL Figures 4 and 6, CL = 100pF, S1 closed, S2 open 0.86 4.00 µs Driver Disable Time from Low tDLZ Figures 4 and 6, CL = 15pF, S1 closed, S2 open 0.4 1.5 µs Driver Disable Time from High tDHZ Figures 4 and 6, CL = 15pF, S2 closed, S1 open 0.6 1.5 µs Receiver Input to Output Propagation Delay tRPLH 5.2 12 6.4 12 Differential Receiver Skew (tRPLH - tRPHL) tRPHL tRSKEW Figures 7 and 9, CL = 15pF, |VID| = 2V 1.2 Figures 7 and 9, |VID| = 2V µs µs Data Rate fMAX Figure 9, CL = 100pF 64 kbps Receiver Enable Time to Output Low tRZL Figures 2 and 8, CL = 15pF, S1 closed, S2 open 70 500 ns Receiver Enable Time to Output High tRZH Figures 2 and 8, CL = 15pF, S2 closed, S1 open 85 500 ns Receiver Disable Time from Low tRLZ Figures 2 and 8, CL = 15pF, S1 closed, S2 open 50 200 ns Receiver DisableTime from High tRHZ Figures 2 and 8, CL = 15pF, S2 closed, S1 open 35 200 ns Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referred to device ground unless otherwise noted. Note 2: ∆VOD and ∆VOC are the changes in magnitude of VOD and VOC, respectively, when the DI input changes state. Note 3: Maximum and minimum current levels apply to peak current just prior to foldback-current limiting. _______________________________________________________________________________________ 3 MAX3471 DC ELECTRICAL CHARACTERISTICS (continued) __________________________________________Typical Operating Characteristics (VCC = +3.6V, TA = +25°C, unless otherwise noted.) OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE 30 VCC = 5V 20 15 VCC = 3.6V VCC = 5V 12 10 8 6 10 4 5 2 VCC = 3.6V 4.5 4.0 VCC = 3.6V 3.5 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 -50 -25 0 25 50 75 100 125 OUTPUT HIGH VOLTAGE (V) TEMPERATURE (°C) RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE VCC = 3.6V 80 60 VCC = 5V 40 30 25 20 15 5 0 0 0 25 50 75 100 VCC = 3.6V 10 20 -25 VCC = 5V MAX3471toc06 1.0 0.8 VCC = 3.6V 0.6 0.4 RDIFF = 54Ω -50 -25 60 VCC = 5V 3.5 VCC = 3.6V 2.5 2.0 1.5 1.0 25 50 75 100 125 OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE (VCC = 3.6V) 30 VCC = 3.6V 25 OUTPUT CURRENT (mA) 50 OUTPUT CURRENT (mA) VCC = 5V 0 TEMPERATURE (°C) OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE (VCC = 5V) MAX3471toc07 5.0 3.0 VCC = 5V 1.2 DIFFERENTIAL OUTPUT VOLTAGE (V) DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE 4.0 1.4 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 TEMPERATURE (°C) 4.5 1.6 0 0 125 1.8 0.2 MAX3471toc08 100 35 2.0 DIFFERENTIAL OUTPUT VOLTAGE (V) 120 40 MAX3471toc05 MAX3471toc04 LOAD = 2.2mA 40 30 20 20 15 10 5 10 0.5 VCC = 5V OUTPUT LOW VOLTAGE (V) 140 -50 5.0 3.0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 DRIVER OUTPUT CURRENT (mA) 0 RDIFF = 1.5kΩ 0 0 0 -50 -25 0 25 50 75 TEMPERATURE (°C) 4 LOAD = 0.8mA 0 0 RECEIVER OUTPUT VOLTAGE (mV) 14 MAX3471toc03 16 5.5 MAX3471toc09 25 18 OUTPUT CURRENT (mA) 35 MAX3471toc02 40 OUTPUT CURRENT (mA) 20 MAX3471toc01 45 RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE RECEIVER OUTPUT VOLTAGE (V) OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE DIFFERENTIAL OUTPUT VOLTAGE (V) MAX3471 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems 100 125 0 1 2 3 4 5 6 7 OUTPUT LOW VOLTAGE (V) 8 9 10 0 2 4 6 8 OUTPUT LOW VOLTAGE (V) _______________________________________________________________________________________ 10 12 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems 30 25 20 15 10 SUPPLY CURRENT (µA) 20 15 10 80 VCC = 5.5V 70 VCC = 5.0V MAX3471toc12 VCC = 3.6V OUTPUT CURRENT (mA) 35 90 MAX3471toc11 VCC = 5V 60 50 VCC = 3.6V 40 30 VCC = 2.5V 20 5 10 5 0 -6 -4 -2 0 2 4 -12 6 -10 -8 -6 -4 -2 0 2 VCC = 5.5V 25 1.5 VCC = 5.0V 2.0 VCC = 3.6V 1.5 VCC = 2.5V VCC = 3.6V, RDIFF = 1.5kΩ 1.4 PROPAGATION DELAY (µs) SUPPLY CURRENT (µA) 0 50 75 100 125 DRIVER PROPAGATION DELAY (tDPHL, tDPLH) vs. TEMPERATURE MAX3471toc13 3.0 1.0 -25 TEMPERATURE (°C) NO-LOAD SUPPLY CURRENT vs. TEMPERATURE (DE = GND) 2.5 -50 4 OUTPUT HIGH VOLTAGE (V) OUTPUT HIGH VOLTAGE (V) 0.5 MAX3471toc14 -8 VCC = 5V, RDIFF = 1.5kΩ 1.3 1.2 1.1 VCC = 5V, RDIFF = 54Ω 1.0 VCC = 3.6V, RDIFF = 54Ω 0.9 0.8 CL1 = CL2 = 100pF DE = GND 0 0.7 -50 -25 0 25 50 75 100 125 -40 -20 0 TEMPERATURE (°C) RECEIVER PROPAGATION DELAY (tPLH) vs. TEMPERATURE VCC = 3.6V 4 VCC = 5V 3 2 -20 0 20 80 100 7.0 VCC = 3.6V 6.5 6.0 5.5 5.0 VCC = 5V 4.5 4.0 CIRCUIT OF FIGURE 9 CL = 100pF |VID| = 2V -40 60 7.5 PROPAGATION DELAY (µs) 5 0 40 RECEIVER PROPAGATION DELAY (tPHL) vs. TEMPERATURE MAS3471toc15 6 1 20 TEMPERATURE (°C) MAX3471toc16 -12 -10 DE = VCC 0 0 PROPAGATION DELAY (µs) OUTPUT CURRENT (mA) 25 MAX3471toc10 45 40 NO-LOAD SUPPLY CURRENT vs. TEMPERATURE (DE = VCC) OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE (VCC = 3.6V) OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE (VCC = 5V) |VID| = 2V 3.5 CL = 100pF 3.0 40 60 TEMPERATURE (°C) 80 100 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX3471 Typical Operating Characteristics (continued) (VCC = +3.6V, TA = +25°C, unless otherwise noted.) MAX3471 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems Typical Operating Characteristics (continued) (VCC = +3.6V, TA = +25°C, unless otherwise noted.) DRIVER PROPAGATION DELAY RECEIVER PROPAGATION DELAY MAX3471toc17 MAX3471toc18 B A (2V/div) (2V/div) A B DI (2V/div) DI (2V/div) A-B (2V/div) RO (2V/div) A-B (1V/div) 400ns/div 1µs/div R = 1.5kΩ, CL = 100pF ______________________________________________________________Pin Description PIN NAME FUNCTION 1 RO Receiver Output. When RE is low, if A - B ≥ -50mV, RO will be high; if A - B ≤ -450mV, RO will be low. 2 RE Receiver Output Enable. Drive RE low to enable RO; RO is high impedance when RE is high. 3 DE Driver Output Enable. Drive DE high to enable the driver outputs. These outputs are high impedance when DE is low. 4 DI Driver Input. With DE high, a low on DI forces the noninverting output low and the inverting output high. Similarly, a high on DI forces the noninverting output high and the inverting output low. 5 GND 6 A Noninverting Driver Output and Noninverting Receiver Input 7 B Inverting Driver Output and Inverting Receiver Input 8 VCC Ground Positive Supply: +2.5V ≤ VCC ≤ +5.5V _______________Detailed Description The MAX3471 half-duplex transceiver consumes only 1.6µA from a single +3.6V supply. Its wide 2.5V to 5.5V supply voltage guarantees operation over the lifetime of a lithium battery. This device contains one driver and one receiver. Its true fail-safe receiver input guarantees a logic-high receiver output when the receiver inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers disabled. Reduced-slew-rate drivers minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 64kbps. Receiver Input Filtering The MAX3471 receiver operates at up to 64kbps and incorporates input filtering in addition to input hystere6 sis. This filtering enhances noise immunity when differential signals have very slow rise and fall times. The MAX3471 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 accomplished by setting the receiver threshold between -50mV and -450mV. If the differential receiver input voltage (A-B) is greater than or equal to -50mV, RO is a logic high. If A-B is less than or equal to -450mV, RO is a logic low. In the case of a terminated bus with all transmitters disabled, the receiver’s differential input voltage is pulled to 0V by the termination. With the MAX3471’s receiver thresholds, this results in a logic high with a 50mV minimum noise margin. _______________________________________________________________________________________ 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems Table 2. Receiving INPUTS OUTPUTS INPUTS OUTPUT RE DE DI B A RE DE A-B RO X 1 1 0 1 0 0 ≥ -0.05V 1 X 1 0 1 0 0 0 ≤ -0.45V 0 0 0 X ZD ZD 0 0 Open/Shorted 1 1 0 X ZD ZD 1 0 X Z ZD = Driver output disabled MAX3471 Table 1. Transmitting X = Don’t care Z = Receiver output high impedance __________ Applications Information Transceivers on the Bus The MAX3471 is optimized for the unterminated bus normally used in slow, low-power systems. With a +2.5V supply, the part is guaranteed to drive up to eight standard loads (for example, 64 other MAX3471s or 56 MAX3471s plus one standard load). Drive capability increases significantly with supply. For example, with a +5V supply, the MAX3471 typically meets the RS-485 driver output specifications (1.5V with 54Ω differential termination). See the Typical Operating Characteristics. A R Reduced EMI and Reflections The MAX3471 is slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. In general, the rise time of a transmitter directly relates to the length of an unterminated stub, which can be driven with only minor waveform reflections. The following equation expresses this relationship conservatively: Length = tRISE / (10 x 1.5ns/foot) where tRISE is the transmitter’s rise time. For example, the MAX3471’s rise time is typically 1.3µs, which results in excellent waveforms with a stub length up to 82 feet. In general, systems operate well with longer unterminated stubs, even with severe reflections, if the waveform settles out before the UART samples them. Driver Output Protection Excessive output current and power dissipation caused by faults or bus contention are prevented by foldback current limiting. A foldback current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range (see Typical Operating Characteristics). VOD R VOC B Figure 1. Driver DC Test Load VCC S1 RECEIVER OUTPUT TEST POINT VCC DE 1k CL1 A DI CL S2 Figure 2. Receiver Enable/Disable Timing Test Load VO DRIVER B RDIFF CL2 Figure 3. Driver Test Circuit _______________________________________________________________________________________ 7 MAX3471 1.6µA, RS-485/RS-422, Half-Duplex, Differential Transceiver for Battery-Powered Systems V CC DI 0V VCC S1 V CC 2 V CC 2 t DPLH 12k B OUTPUT UNDER TEST t DPHL VO A 1/2 V O 1/2 V O CL V DIFF = V (A) - V (B) VO VDIFF 0V -VO S2 90% 10% 90% t DR 10% t DF t DSKEW = (t DPLH - t DPHL ) Figure 4. Driver Enable/Disable Timing Test Load V CC DE 0V V CC 2 V CC 2 t DZL t DLZ V CC 2 OUTPUT NORMALLY LOW V TEST A, B VOL VOL + 0.5V 1.4V 1.4V OUTPUT t RPHL t RPLH A INPUT VOH - 0.5V V CC 2 t DZH t DHZ | V ID | = 2V t RSKEW = (t RPLH = t RPHL ) V TEST = 0.91V CC Figure 7. Receiver Propagation Delay Figure 6. Driver Enable and Disable Times V CC RE 0V V OH RO V OL B OUTPUT NORMALLY HIGH VOH A, B 0V Figure 5. Driver Differential Propagation Delay and Rise/Fall Times V CC 2 V CC 2 t RZL t RLZ VCC RO VOL 1.4V OUTPUT NORMALLY LOW VOH RO 0V OUTPUT NORMALLY HIGH A RECEIVER OUTPUT RECEIVER CL VOL + 0.5V VOH - 0.5V 1.4V t RZH B VID t RHZ RE Figure 9. Receiver Propagation Delay and Maximum DataRate Test Circuit ___________________Chip Information Figure 8. Receiver Enable and Disable Times TRANSISTOR COUNT: 351 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. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.