DS36C278 Low Power Multipoint EIA-RS-485 Transceiver General Description Features The DS36C278 is a low power differential bus/line transceiver designed to meet the requirements of RS-485 standard for multipoint data transmission. In addition it is compatible with TIA/EIA-422-B. The CMOS design offers significant power savings over its bipolar and ALS counterparts without sacrificing ruggedness against ESD damage. The device is ideal for use in battery powered or power conscious applications. ICC is specified at 500 µA maximum. The driver and receiver outputs feature TRI-STATE ® capability. The driver outputs operate over the entire common mode range of −7V to +12V. Bus contention or fault situations that cause excessive power dissipation within the device are handled by a thermal shutdown circuit, which forces the driver outputs into the high impedance state. The receiver incorporates a fail safe circuit which guarantees a high output state when the inputs are left open. (Note 1) The DS36C278T is fully specified over the industrial temperature range (−40˚C to +85˚C). n 100% RS-485 compliant — Guaranteed RS-485 device interoperation n Low power CMOS design: ICC 500 µA max n Built-in power up/down glitch-free circuitry — Permits live transceiver insertion/displacement n DIP and SOIC packages available n Industrial temperature range: −40˚C to +85˚C n On-board thermal shutdown circuitry — Prevents damage to the device in the event of excessive power dissipation n Wide common mode range: −7V to +12V n Receiver open input fail-safe (Note 1) n 1⁄4 unit load (DS36C278): ≥128 nodes n 1⁄2 unit load (DS36C278T): ≥64 nodes n ESD (human body model): ≥2 kV n Drop in replacement for: — LTC485, MAX485, DS75176, DS3695 Connection Diagram 01204001 Order Number DS36C278TM, DS36C278TN, DS36C278M, DS36C278N See NS Package Number M08A or N08E Truth Table DRIVER SECTION RE* DE DI DO/RI DO*/RI* X H H H L X H L L H X L X Z Z RECEIVER SECTION RE* DE RI-RI* RO H L L ≥+0.2V L L ≤−0.2V L H L X Z L L OPEN (Note 1) H Note 1: Non-terminated, open input only TRI-STATE ® is a registered trademark of National Semiconductor Corporation. © 2004 National Semiconductor Corporation DS012040 www.national.com DS36C278 Low Power Multipoint EIA-RS-485 Transceiver July 1998 DS36C278 Absolute Maximum Ratings (Note 2) Storage Temperature Range If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Lead Temperature (Soldering 4 sec) Supply Voltage (VCC) Recommended Operating Conditions Input Voltage (DE, RE*, & DI) +12V −0.5V to (VCC +0.5V) Common Mode (VCM) ± 15V ± 14V Driver Output/Receiver Input Input Voltage (DO/RI, DO*/RI*) Receiver Output Voltage Supply Voltage (VCC) +260˚C Min Typ Max Units +4.75 +5.0 +5.25 V +12 V Bus Voltage −0.5V to (VCC +0.5V) −65˚C to +150˚C −7 Operating Free Air Temperature (Ta) Maximum Package Power Dissipation @ +25˚C DS36C278T M Package 1190 mW, derate 9.5 mW/˚C above +25˚C DS36C278 N Package 744 mW, derate 6.0 mW/˚C above +25˚C −40 25 +85 ˚C 0 25 +70 ˚C Electrical Characteristics (Notes 3, 4) Over Supply Voltage and Operating Temperature ranges, unless otherwise specified Symbol Parameter Conditions Reference Min Typ Max Units 5.0 V DIFFERENTIAL DRIVER CHARACTERISTICS VOD1 Differential Output Voltage IO = 0 mA (No Load) VOD0 Output Voltage IO = 0 mA VOD0* Output Voltage (Output to GND) VOD2 Differential Output Voltage RL = 50Ω (422) (Termination Load) RL = 27Ω (485) Balance of VOD2 RL = 27Ω or 50Ω ∆VOD2 (422) (485) Figure 1 (Note 5) |VOD2 − V0D2*| 1.5 0 5.0 V 0 5.0 V 2.0 2.8 V 1.5 2.3 5.0 V −0.2 0.1 +0.2 V 1.5 2.0 5.0 V 0 3.0 V 0 3.0 V −0.2 +0.2 V (422, 485) VOD3 Differential Output Voltage (Full Load) R1 = 54Ω, R2 = 375Ω VTEST = −7V to +12V VOC Driver Common Mode Output Voltage RL = 27Ω (485) RL = 50Ω (422) ∆VOC Balance of VOC |VOC − VOC*| RL = 27Ω or RL = 50Ω IOSD Driver Output Short-Circuit Current VO = +12V (485) Figure 4 200 +250 mA VO = −7V (485) −190 −250 mA +0.035 +0.2 V Figure 2 Figure 1 (Note 5) (422, 485) RECEIVER CHARACTERISTICS VTH Differential Input High Threshold Voltage VO = VOH, IO = −0.4V −7V ≤ VCM ≤ +12V VTL Differential Input Low Threshold Voltage VO = VOL, IO = 0.4 mA −7V ≤ VCM ≤ +12V VHST Hysteresis VCM = 0V RIN Input Resistance −7V ≤ VCM ≤ +12V RIN Input Resistance −7V ≤ VCM ≤ +12V IIN Line Input Current Other Input = 0V, (Note 8) DE = VIL, RE* = VIL, VCC= 4.75 to 5.25 (Note 6) (422, 485) Line Input Current Glitch Other Input = 0V, (Note 8) DE = VIL, RE* = VIL, VCC = +3.0V or 0V, DS36C278 DS36C278T DS36C278 DS36C278T TA = 25˚C www.national.com −0.035 V 70 mV DS36C278T 24 68 kΩ (Note 7) or 0V IING −0.2 2 DS36C278 48 68 VIN = +12V 0 0.19 0.25 mA kΩ VIN = −7V 0 −0.1 −0.2 mA VIN = +12V 0 0.19 0.5 mA VIN = −7V 0 −0.1 −0.4 mA VIN = +12V 0 0.19 0.25 mA VIN = −7V 0 −0.1 −0.2 mA VIN = +12V 0 0.19 0.5 mA VIN = −7V 0 −0.1 −0.4 mA (Continued) Over Supply Voltage and Operating Temperature ranges, unless otherwise specified Symbol Parameter Conditions Reference Min Typ 3.5 4.6 Max Units ± 400 mV RECEIVER CHARACTERISTICS IB Input Balance Test RS = 500Ω VOH High Level Output Voltage IOH = −4 mA, VID = +0.2V VOL Low Level Output Voltage IOL = +4 mA, VID = −0.2V IOSR Short Circuit Current VO = GND IOZR TRI-STATE Leakage Current VO = 0.4V to 2.4V (422) (Note 10) RO Figure 11 7 RO V 0.3 0.5 V 35 85 mA ±1 µA DEVICE CHARACTERISTICS VIH High Level Input Voltage 2.0 VCC V VIL Low Level Input Voltage GND 0.8 V IIH High Level Input Current VIH = VCC 2 µA IIL Low Level Input Current VCC = 5V −2 µA DE, RE*, DI VCC = +3.0V VIL = 0V ICC Power Supply Current Driver and Receiver ON ICCR (No Load) Driver OFF, Receiver ON ICCD Driver ON, Receiver OFF ICCZ Driver and Receiver OFF VCC −2 µA 200 500 µA 200 500 µA 200 500 µA 200 500 µA Switching Characteristics (Notes 4, 9) Over Supply Voltage and Operating Temperature ranges, unless otherwise specified Symbol Parameter Conditions Reference Min Typ Max Units 10 39 80 ns 10 40 80 ns 0 1 10 ns ns DRIVER CHARACTERISTICS tPHLD Differential Propagation Delay High to Low tPLHD Differential Propagation Delay Low to High tSKD Differential Skew |tPHLD − tPLHD| RL = 54Ω, CL = 100 pF Figures 5, 6 tr Rise Time 3 25 50 tf Fall Time 3 25 50 ns tPHZ Disable Time High to Z CL = 15 pF Figures 7, 8 — 80 200 ns tPLZ Disable Time Low to Z RE * = L Figures 9, 10 — 80 200 ns tPZH Enable Time Z to High CL = 100 pF Figures 7, 8 — 50 200 ns tPZL Enable Time Z to Low RE * = L Figures 9, 10 — 65 200 ns 30 210 400 ns 30 190 400 ns 0 20 50 ns — 50 150 ns — 55 150 ns — 40 150 ns — 45 150 ns RECEIVER CHARACTERISTICS tPHL Propagation Delay High to Low tPLH Propagation Delay Low to High tSK Skew, |tPHL − tPLH| tPLZ Output Disable Time CL = 15 pF Figures 12, 13 CL = 15 pF tPHZ tPZL Figures 14, 15, 16 Output Enable Time tPZH 3 www.national.com DS36C278 Electrical Characteristics (Notes 3, 4) DS36C278 Switching Characteristics (Notes 4, 9) (Continued) Note 2: “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices should be operated at these limits. The table of “Electrical Characteristics” specifies conditions of device operation. Note 3: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except VOD1 and VOD2. Note 4: All typicals are given for: VCC = +5.0V, TA = + 25˚C. Note 5: Delta |VOD2| and Delta |VOC| are changes in magnitude of VOD2 and VOC, respectively, that occur when input changes state. Note 6: Threshold parameter limits specified as an algebraic value rather than by magnitude. Note 7: Hysteresis defined as VHST = VTH − VTL. Note 8: IIN includes the receiver input current and driver TRI-STATE leakage current. Note 9: CL includes probe and jig capacitance. Note 10: For complete details of test, see RS-485. Parameter Measurement Information 01204002 01204005 FIGURE 1. Driver VOD2 and VOC FIGURE 5. Driver Differential Propagation Delay Test Circuit 01204018 FIGURE 2. Driver VOD3 01204003 FIGURE 3. Driver VOH and VOL 01204006 FIGURE 6. Driver Differential Propagation Delays and Differential Rise and Fall Times 01204004 Vtest = −7V to +12V FIGURE 4. Driver IOSD www.national.com 4 DS36C278 Parameter Measurement Information (Continued) 01204010 FIGURE 10. TRI-STATE Waveforms (tPZL, tPLZ) 01204007 FIGURE 7. TRI-STATE Test Circuit (tPZH , tPHZ) 01204011 FIGURE 11. Receiver VOH and VOL 01204008 FIGURE 8. TRI-STATE Waveforms (tPZH, tPHZ) 01204012 FIGURE 12. Receiver Differential Propagation Delay Test Circuit 01204009 FIGURE 9. TRI-STATE Test Circuit (tPZL, tPLZ) 01204013 FIGURE 13. Receiver Differential Propagation Delay Waveforms 5 www.national.com DS36C278 Parameter Measurement Information (Continued) 01204014 FIGURE 14. Receiver TRI-STATE Test Circuit 01204015 FIGURE 15. Receiver Enable and Disable Waveforms (tPLZ, tPZL) 01204016 FIGURE 16. Receiver Enable and Disable Waveforms (tPHZ, tPZH) www.national.com 6 DS36C278 Typical Application Information 01204017 FIGURE 17. Typical RS-485 Bus Interface TABLE 1. Device Pin Descriptions Pin No. Name Description 1 RO Receiver Output: When RE (Receiver Enable) is LOW, the receiver is enabled (ON), if DO/RI ≥ DO*/RI* by 200 mV, RO will be HIGH. If DO/RI ≤ DO*/RI* by 200 mV, RO will be LOW. Additionally RO will be HIGH for OPEN (Non-terminated) Inputs. 2 RE* Receiver Output Enable: When RE* is LOW the receiver output is enabled. When RE* is HIGH, the receiver output is in TRI-STATE (OFF). 3 DE Driver Output Enable: When DE is HIGH, the driver outputs are enabled. When DE is LOW, the driver outputs are in TRI-STATE (OFF). 4 DI Driver Input: When DE (Driver Enable) is HIGH, the driver is enabled, if DI is LOW, then DO/RI will be LOW and DO*/RI* will be HIGH. If DI is HIGH, then DO/RI is HIGH and DO*/RI* is LOW. 5 GND Ground Connection. 6 DO/RI Driver Output/Receiver Input, 485 Bus Pin. 7 DO*/RI* Driver Output/Receiver Input, 485 Bus Pin. 8 VCC Positive Power Supply Connection: Recommended operating range for VCC is +4.75V to +5.25V. First, for a 1⁄2 UL device the top and bottom borders shown in Figure 18 are scaled. Both 0 mA reference points at +5V and −3V stay the same. The other reference points are +12V at +0.5 mA for the top border and −7V at −0.4 mA for the bottom border (see Figure 18 ). Second, for a 1⁄4 UL device the top and bottom borders shown in Figure 18 are scaled also. Again, both 0 mA reference points at +5V and −3V stay the same. The other reference points are +12V at +0.25 mA for the top border and −7V at −0.2 mA for the bottom border (see Figure 18 ). The advantage of the 1⁄2 UL and 1⁄4 UL devices is the increased number of nodes on one bus. In a single master multi-slave type of application where the number of slaves exceeds 32, the DS36C278/279/280 may save in the cost of extra devices like repeaters, extra media like cable, and/or extra components like resistors. The DS36C279 and DS36C280 have an additional feature which offers more advantages. The DS36C279 has an automatic sleep mode function for power conscious applications. The DS36C280 has a slew rate control for EMI conscious applications. Refer to the sleep mode and slew rate control portion of the application information section in the corresponding datasheet for more information on these features. Unit Load A unit load for an RS-485 receiver is defined by the input current versus the input voltage curve. The gray shaded region is the defined operating range from −7V to +12V. The top border extending from −3V at 0 mA to +12V at +1 mA is defined as one unit load. Likewise, the bottom border extending from +5V at 0 mA to −7V at −0.8 mA is also defined as one unit load (see Figure 18 ). An RS-485 driver is capable of driving up to 32 unit loads. This allows up to 32 nodes on a single bus. Although sufficient for many applications, it is sometimes desirable to have even more nodes. For example, an aircraft that has 32 rows with 4 seats per row would benefit from having 128 nodes on one bus. This would allow signals to be transferred to and from each individual seat to 1 main station. Usually there is one or two less seats in the last row of the aircraft near the restrooms and food storage area. This frees the node for the main station. The DS36C278, the DS36C279, and the DS36C280 all have 1⁄2 unit load and 1⁄4 unit load (UL) options available. These devices will allow up to 64 nodes or 128 nodes guaranteed over temperature depending upon which option is selected. The 1⁄2 UL option is available in industrial temperature and the 1⁄4 UL is available in commercial temperature. 7 www.national.com DS36C278 Unit Load (Continued) 01204019 FIGURE 18. Input Current vs Input Voltage Operating Range www.national.com 8 DS36C278 Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC Order Number DS36C278TM, DS36C278M NS Package Number M08A 9 www.national.com DS36C278 Low Power Multipoint EIA-RS-485 Transceiver Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Lead (0.300" Wide) Molded Dual-In-Line Package Order Number DS36C278TN, DS36C278N NS Package Number N08E National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. 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