DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode General Description Features The DS481 is a low-power transceiver for RS-485 and RS422 communication. The device contains one driver and one receiver. The drivers slew rate allows for operation up to 2.0 Mbps (see Applications Information section). The transceiver draws 200 µA of supply current when unloaded or 0.2 µA when in the automatic sleep mode. Sleep mode is activated by inactivity on the enables (DE and RE (Note 1)). Holding DE =L and RE (Note 1)=H for greater than 600 ns will enable the sleep mode. The DS481 operates from a single +5V supply. n n n n n n n The driver is short-circuit current limited and is protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into TRI-STATE ® (High Impedance state) under fault conditions. The driver guarantees a minimum of 1.5V differential output voltage with maximum loading across the common mode range (VOD3). The receiver has a failsafe feature that guarantees a logichigh output if the input is open circuit. The DS481 is available in a surface mount package and is characterized for Industrial temperature range operation. Connection and Logic Diagram n n n n n n Meets TIA/EIA RS-485 multipoint standard Sleep mode reduces ICC to 0.2 µA Guaranteed full load output voltage (V OD3) Low quiescent current: 200 µA typ −7V to +12V common-mode input voltage range TRI-STATE outputs on driver and receiver AC performance: — Driver transition time: 25 ns typ — Driver propagation delay: 40 ns typ — Driver skew: 1 ns typ — Receiver propagation delay: 200 ns typ — Receiver skew: 20 ns typ Half-duplex flow through pinout Operates from a single 5V supply Allows up to 64 tranceivers on the bus Current-limiting and thermal shutdown for driver overload protection Industrial temperature range operation Pin and functional compatible with MAX481C and MAX481E Truth Table DRIVER SECTION RE (Note 1) DE DI A B X H H H L X H L L H X L X Z Z (Note 2) RECEIVER SECTION 01291901 *Note: Non Terminated, Open Input only Order Number DS481TM Temp. Range −40˚C to +85˚C Package/### SOP/M08A RE (Note 1) DE A-B RO L L L ≥+0.2V H L ≤−0.2V L H X X Z (Note 2) L L OPEN (Note 1) H X = indeterminate Z = TRI-STATE Note 1: Non Terminated, Open Input only Note 2: Device enters sleep mode if enable conditions are held > 600 ns, DE = L and RE (Note 1) = H. TRI-STATE ® is a registered trademark of National Semiconductor Corporation. © 2004 National Semiconductor Corporation DS012919 www.national.com DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode July 2000 DS481 Absolute Maximum Ratings (Note 3) M Package 0.76W If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Storage Temperature Range Supply Voltage (VCC) ESD (HBM) (Soldering, 4 sec.) +12V Enable Input Voltage (RE (Note 1), DE) −0.5V to (VCC + 0.5V) Driver Input Voltage (DI) −0.5V to (VCC + 0.5V) Driver Output Voltage (A, B) Receiver Output Voltage (RO) +260˚C ≥2 kV Recommended Operating Conditions −14V to +14V Receiver Input Voltage (A, B) −65˚C to +150˚C Lead Temperature Range Min −14V to +14V Supply Voltage (VCC) −0.5V to (VCC + 0.5V) Max Units V Operating Free Air Maximum Package Power Dissipation @ +25˚C M Package Typ +4.75 +5.0 +5.25 Temperature (TA) 1.19W DS481T Derate M Package 9.5 mW/˚C above +25˚C −40 Bus Common Mode Voltage +25 −7 +85 ˚C +12 V Maximum Package Power Dissipation @ +70˚C Electrical Characteristics Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 4, 5) Symbol Parameter Conditions Pin Min Typ Max Units A, B 1.5 VOD1 Differential Driver Output Voltage (No Load) VOD2 Differential Driver Output Voltage RL = 50Ω, (RS422), Figure 1 2 2.8 with Load RL = 27Ω, (RS485), Figure 1 1.5 2.3 Change in Magnitude of Output RL = 27Ω or 50Ω (Note 6) ∆VOD 5 V V 5 V 0.2 |V| 5 V Differential Voltage VOD3 Differential Driver Output Voltage — R1 = 54Ω, R2 = 375Ω Full Load with Max VCM VTEST = −7V to +12V, Figure 2 1.5 VOC Driver Common-Mode Output Voltage RL = 27Ω or 50Ω, Figure 1 ∆VOC Change in Magnitude of Common-Mode RL = 27Ω or 50Ω, Figure 1 Output Voltage (Note 6) 2.0 0 3 V 0.2 |V| VIH Input High Voltage VIL Input Low Voltage IIN1 Input Current VIN = 0V or VCC IIN2 Input Current (Note 7) DE = 0V, VCC = 0V or 5.25V VIN = +12V VTH Receiver Differential Threshold Voltage −7V ≤ VCM ≤ +12V ∆VTH Receiver Input Hysteresis VCM = 0V VOH Receiver Output High Voltage IO = −4 mA, VID = 0.2V VOL Receiver Output Low Voltage IO = 4 mA, VID = −0.2V 0.5 V IOZR TRI-STATE Output Current at Receiver 0.4V ≤ V ±1 µA RIN Receiver Input Resistance −7V ≤ VIN ≤ +12V ICC No-Load Supply Current (Note 8) DE = V DI, DE, RE (Note 1) DS481T A, B VIN = −7V 2.0 0 0 V 0.8 V ±2 µA 500 µA −100 −400 µA 190 −0.2 0.2 70 O CC, RO 3.5 V ≤ 2.4V DS481T A, B RE (Note 1) = 0V or V V CC V mV 24 kΩ 200 500 µA 200 500 µA 0.2 10 µA CC DE = 0V, RE (Note 1) = 0V or VCC ICCX Sleep Mode Supply Current IOSD1 Driver Short Circuit Current, VO = HIGH −7V ≤ VO ≤ +12V IOSD2 Driver Short Circuit Current, VO = LOW −7V ≤ VO ≤ +12V IOSR Receiver Short Circuit Current VO = GND DE = GND VCC RE (Note 1)= VCC (Figure 14) www.national.com 2 A, B RO 7 250 mA −250 mA 85 mA DS481 Switching Characteristics Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 5, 9, 10) Symbol Parameter tPLHD Driver Differential Propagation Delay — Low to High tPHLD tSKEW Conditions RL = 54Ω, CL = 100 pF Min Typ Max Units 10 40 80 ns Driver Differential Propagation Delay — High to Low 10 39 80 ns Differential Skew |tPHLD − tPLHD| 0 1 10 ns tr Driver Rise Time 3 25 50 ns tf Driver Fall Time 3 25 50 ns tZH Driver Enable to Output High CL = 100 pF 50 200 ns tZL Driver Enable to Output Low CL = 100 pF 65 200 ns tLZ Driver Disable from Output Low CL = 15 pF 80 200 ns tHZ Driver Disable from Output High CL = 15 pF tPSH Driver Enable from Sleep CL = 100 pF Mode to Output High (Note 12) (Figures 5, 6) Driver Enable from Sleep CL = 100 pF tPSL Mode to Output Low (Note 12) (Figures 7, 8) tPLHD Receiver Differential Propagation Delay — Low to High CL = 15 pF (RO) tPHLD Receiver Differential Propagation Delay — High to Low tSKEW Differential Skew |tPHLD − tPLHD| tZH Receiver Enable to Output High tZL 80 200 ns 70 98 250 ns 70 98 250 ns 30 190 400 ns 30 210 400 ns 20 50 ns 45 150 ns Receiver Enable to Output Low 40 150 ns tLZ Receiver Disable from Output Low 50 150 ns tHZ Receiver Disable from Output High 55 150 ns tPSH Receiver Enable from Sleep CL = 15 pF 70 97 250 ns Mode to Output High (Note 12) (Figures 11, 13) 70 95 250 ns 600 ns tPSL 0 CL = 15 pF Receiver Enable from Sleep CL = 15 pF Mode to Output Low (Note 12) (Figures 11, 12) tSLEEP Time to Sleep (Device) DE = L and RE (Note 1) = H fmax Maximum Data Rate (Note 11) 50 (Figure 14) 2.0 Mbps Note 3: “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 4: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except VOD1/2/3and VID. Note 5: All typicals are given for: VCC = +5.0V, TA = +25˚C. Note 6: ∆|VOD| and ∆|VOC| are changes in magnitude of V OD and VOC respectively, that occur when the input changes state. Note 7: IIN2 includes the receiver input current and driver TRI-STATE leakage current. Note 8: Supply current specification is valid for loaded transmitters when DE = 0V or enabled (DE = H) with no load. Note 9: f = 1 MHz, tr and tf ≤ 6 ns, ZO = 50Ω. Note 10: CL includes jig and probe capacitance. Note 11: fmax is the guaranteed data rate for 50 ft of twisted pair cable. f max may be conservatively determined from the ratio of driver transition time (tr) to the data rate unit interval (1/fmax). Using a 10% ratio yields fmax = (0.1)/50 ns = 2.0 Mb/s. Higher data rates may be supported by allowing larger ratios. Note 12: For enable from sleep mode delays DE = L and RE (Note 1) = H for greater than 600 ns prior to test (device is in sleep mode). 3 www.national.com DS481 Parameter Measurement Information 01291906 01291902 FIGURE 5. FIGURE 1. VOD 01291907 FIGURE 6. 01291903 FIGURE 2. VOD3 01291908 01291904 FIGURE 7. FIGURE 3. 01291909 FIGURE 8. 01291910 01291905 FIGURE 9. FIGURE 4. www.national.com 4 DS481 01291911 FIGURE 10. 01291912 FIGURE 11. 01291913 FIGURE 12. 01291914 FIGURE 13. 5 www.national.com DS481 Parameter Measurement Information (Continued) 01291915 *Note: Non Terminated, Open Input only FIGURE 14. Entering Sleep Mode Conditions (modes and exit parameters shown) 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 (Note 1)/RI (Note 1) by 200 mV, RO will be HIGH. If DO/RI ≤ DO (Note 1)/RI (Note 1) by 200 mV, RO will be LOW. Additionally RO will be HIGH for OPEN (Non-terminated) Inputs. 2 RE (Note 1) Receiver Output Enable: When RE (Note 1) is LOW the receiver output is enabled. When RE (Note 1) is HIGH, the receiver output is in TRI-STATE (OFF). When RE (Note 1) is HIGH and DE is LOW, the device will enter a low-current sleep mode after 600 ns. 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). When RE (Note 1) is HIGH and DE is LOW, the device will enter a low-current sleep mode after 600 ns. 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 (Note 1)/RI (Note 1) will be HIGH. If DI is HIGH, then DO/RI is HIGH and DO (Note 1)/RI (Note 1) is LOW. 5 GND Ground Connection. 6 DO/RI Driver Output/Receiver Input, 485 Bus Pin. 7 DO (Note 1) /RI (Note 1) Driver Output/Receiver Input, 485 Bus Pin. 8 VCC Positive Power Supply Connection: Recommended operating range for VCC is +4.75V to +5.25V. The DS481 has 1⁄2 unit load and will allow up to 64 nodes guaranteed over temperature. For a 1⁄2 UL device the top and bottom borders shown in Figure 15 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 15 ). 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 15 ). 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 15 ). 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. www.national.com 6 the sleep mode is automatic, no external components are required. It may be used as little or as much as the application requires. The more the feature is utilized, the more power it saves. The sleep mode is automatically entered when both the driver and receiver are disabled. This occurs when both the DE pin is asserted to a logic low and the RE (Note 1) pin is asserted to a logic high. Once both pins are asserted the device will enter sleep mode after 50 ns. The DS481 is guaranteed to go into sleep mode within 600 ns after both pins are asserted. The device wakes up (comes out of sleep mode) when either the DE pin is asserted to a logic high and/or the RE (Note 1) pin is asserted to a logic low. After the device enters sleep mode it will take longer for the device to wake up than it does for the device to enable from TRISTATE. Refer to datasheet specifications tPSL and tPSH and compare with tPZL and t PZH for timing differences. (Continued) The advantage of the 1⁄2 UL device 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 DS481 may save in the cost of extra devices like repeaters, extra media like cable, and/or extra components like resistors. The benefit of the DS481 is definitely its power savings. When active the device has a maximum ICC of 500 µA. When in sleep mode the device has a maximum ICC of only 10 µA, which is 50 times less power than when active. The ICC when the device is active is already very low but when in sleep mode the ICCis ultra low. 01291916 FIGURE 15. Input Current vs Input Voltage Operating Range Applications Information Sleep Mode The DS481 features an automatic sleep mode that allows the device to save power when not transmitting data. Since Multipoint RS-485 Application 01291917 7 www.national.com DS481 Unit Load DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode Physical Dimensions inches (millimeters) unless otherwise noted Order Number DS481TM NS Package Number M08A 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. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. 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