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High Speed, ESD-Protected, Full-Duplex, iCoupler(R), Isolated RS-485 Transceiver ADM2490E FEATURES Isolated, full-duplex RS-485/RS-422 transceiver 8 kV ESD protection on RS-485 input/output pins 16 Mbps data rate Complies with ANSI TIA/EIA RS-485-A-1998 and ISO 8482: 1987(E) Suitable for 5 V or 3 V operation (VDD1) High common-mode transient immunity: >25 kV/s Receiver has open-circuit, fail-safe design 32 nodes on the bus Thermal shutdown protection Safety and regulatory approvals pending UL recognition: 5000 V rms isolation voltage for 1 minute per UL 1577 VDE certificate of conformity DIN EN 60747-5-2 (VDE 0884 Part 2): 2003-01 DIN EN 60950 (VDE 0805): 2001-12; EN 60950: 2000 VIORM = 848 VPEAK Operating temperature range: -40C to +105C Wide-body, 16-lead SOIC package FUNCTIONAL BLOCK DIAGRAM VDD1 VDD2 ADM2490E GALVANIC ISOLATION Y Z TxD A B RxD GND1 GND2 Figure 1. GENERAL DESCRIPTION The ADM2490E is an isolated data transceiver with 8 kV ESD protection and is suitable for high speed, full-duplex communication on multipoint transmission lines. It is designed for balanced transmission lines and complies with ANSI TIA/EIA RS-485-A-1998 and ISO 8482: 1987(E). The device employs Analog Devices, Inc., iCoupler technology to combine a 2-channel isolator, a 3-state differential line driver, and a differential input receiver into a single package. The differential transmitter outputs and receiver inputs feature electrostatic discharge circuitry that provides protection to 8 kV using the human body model (HBM). The logic side of the device can be powered with either a 5 V or a 3 V supply, whereas the bus side requires an isolated 5 V supply. The device has current-limiting and thermal shutdown features to protect against output short circuits and situations where bus contention could cause excessive power dissipation. APPLICATIONS Isolated RS-485/RS-422 interfaces Industrial field networks INTERBUS Multipoint data transmission systems Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2006 Analog Devices, Inc. All rights reserved. 05889-001 ADM2490E TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Specifications .................................................................. 4 ADM2490E Characteristics............................................................. 5 Package Characteristics ............................................................... 5 Regulatory Information (Pending) ............................................ 5 Insulation and Safety-Related Specifications............................ 5 VDE 0884 Insulation Characteristics (Pending)...................... 6 Absolute Maximum Ratings............................................................ 7 ESD Caution.................................................................................. 7 Pin Configuration and Functional Descriptions.......................... 8 Test Circuits........................................................................................9 Switching Characteristics .............................................................. 10 Typical Performance Characteristics ........................................... 11 Circuit Description......................................................................... 13 Electrical Isolation...................................................................... 13 Truth Tables................................................................................. 13 Thermal Shutdown .................................................................... 14 Fail-Safe Receiver Inputs ........................................................... 14 Magnetic Field Immunity.......................................................... 14 Applications Information .............................................................. 15 Isolated Power-Supply Circuit .................................................. 15 PC Board Layout ........................................................................ 15 Outline Dimensions ....................................................................... 16 Ordering Guide .......................................................................... 16 REVISION HISTORY 10/06--Revision 0: Initial Version Rev. 0 | Page 2 of 16 ADM2490E SPECIFICATIONS All voltages are relative to their respective ground; 2.7 VDD1 5.5 V, 4.5 V VDD2 5.5 V. All minimum/maximum specifications apply over the entire recommended operation range, unless otherwise noted. All typical specifications are at TA = 25C, VDD1 = VDD2 = 5.0 V, unless otherwise noted. Table 1. Parameter SUPPLY CURRENT Power-Supply Current, Logic Side TxD/RxD Data Rate < 2 Mbps TxD/RxD Data Rate = 16 Mbps Power-Supply Current, Bus Side TxD/RxD Data Rate < 2 Mbps TxD/RxD Data Rate = 16 Mbps DRIVER Differential Outputs Differential Output Voltage, Loaded Symbol Min Typ Max Unit Test Conditions IDD1 IDD1 IDD2 IDD2 3.0 6 4.0 60 mA mA mA mA 2.7 V VDD1 5.5 V, unloaded 100 load between Y and Z 2.7 V VDD1 5.5 V, unloaded 100 load between Y and Z |VOD2| 2.0 1.5 5.0 5.0 5.0 0.2 3.0 0.2 200 V V V V V V mA V V A |VOD4| |VOD| for Complementary Output States Common-Mode Output Voltage |VOC| for Complementary Output States Short-Circuit Output Current Logic Inputs Input Threshold Low Input Threshold High TxD Input Current RECEIVER Differential Inputs Differential Input Threshold Voltage Input Voltage Hysteresis Input Current (A, B) Line Input Resistance Logic Outputs Output Voltage Low Output Voltage High Short Circuit Current COMMON-MODE TRANSIENT IMMUNITY 1 1 1.5 |VOD| VOC |VOC| IOS VILTxD VIHTRxD ITxD 0.25 x VDD1 -10 +0.01 RL = 50 (RS-422), see Figure 3 RL = 27 (RS-485), see Figure 3 -7 V VTEST1 +12 V, see Figure 4 RL = 54 or 100 , see Figure 3 RL = 54 or 100 , see Figure 3 RL = 54 or 100 , see Figure 3 0.7 x VDD1 +10 VTH VHYS II RIN VOLRxD VOHRxD -0.2 70 +0.2 1.0 -0.8 12 0.2 VDD1 - 0.2 0.4 100 25 V mV mA mA k V V mA kV/s VOC = 0 V VOC = 12 V VOC = -7 V VDD1 - 0.3 IORxD = 1.5 mA, VA - VB = -0.2 V IORxD = -1.5 mA, VA - VB = 0.2 V VCM = 1 kV, transient magnitude = 800 V CM is the maximum common-mode voltage slew rate that can be sustained while maintaining specification-compliant operation. VCM is the common-mode potential difference between the logic and bus sides. The transient magnitude is the range over which the common-mode is slewed. The common-mode voltage slew rates apply to both rising and falling common-mode voltage edges. Rev. 0 | Page 3 of 16 ADM2490E TIMING SPECIFICATIONS TA = -40C to +85C Table 2. Parameter DRIVER Maximum Data Rate Propagation Delay Pulse Width Distortion, PWD = |tPYLH - tPYHL|, PWD = |tPZLH - tPZHL| Single-Ended Output Rise/Fall Times RECEIVER Propagation Delay Pulse Width Distortion, PWD = |tPLH - tPHL| Symbol Min 16 tPLH, tPHL tPWD, tPWD tR, tF 45 60 7 20 Typ Max Unit Mbps ns ns ns Test Conditions RL = 54 , CL1 = C L2 = 100 pF, see Figure 6 and Figure 8 RL = 54 , CL1 = CL2 = 100 pF, see Figure 6 and Figure 8 RL = 54 , CL1 = CL2 = 100 pF, see Figure 6 and Figure 8 CL = 15 pF, see Figure 7 and Figure 9 CL = 15 pF, see Figure 7 and Figure 9 tPLH, tPHL tPWD 60 10 ns ns TA = -40C to +105C Table 3. Parameter DRIVER Maximum Data Rate Propagation Delay Pulse Width Distortion, PWD = |tPYLH - tPYHL|, PWD = |tPZLH - tPZHL| Single-Ended Output Rise/Fall Time RECEIVER Propagation Delay Pulse Width Distortion, PWD = |tPLH - tPHL| Symbol Min 10 tPYLH, tPYHL, tPZLH, tPZHL tPWD, tPWD tR, tF 45 60 9 27 Typ Max Unit Mbps ns ns ns Test Conditions RL = 54 , CL1 = CL2 = 100 pF, see Figure 6 and Figure 8 RL = 54 , CL1 = CL2 = 100 pF, see Figure 6 and Figure 8 RL = 54 , CL1 = CL2 = 100 pF, see Figure 6 and Figure 8 CL = 15 pF, see Figure 7 and Figure 9 CL = 15 pF, see Figure 7 and Figure 9 tPLH, tPHL tPWD 60 10 ns ns Rev. 0 | Page 4 of 16 ADM2490E ADM2490E CHARACTERISTICS PACKAGE CHARACTERISTICS Table 4. Parameter Resistance (Input-Output) 1 Capacitance (Input-Output)1 Input Capacitance 2 Input IC Junction-to-Case Thermal Resistance Output IC Junction-to-Case Thermal Resistance 1 2 Symbol RI-O CI-O CI JCI JCO Min Typ 1012 3 4 33 28 Max Unit pF pF C/W C/W Test Conditions f = 1 MHz Thermocouple located at center of package underside Device considered a 2-terminal device: Pins 1, 2, 3, 4, 5, 6, 7, and 8 are shorted together and Pins 9, 10, 11, 12, 13, 14, 15, and 16 are shorted together. Input capacitance is from any input data pin to ground. REGULATORY INFORMATION (PENDING) Table 5. UL To be recognized under 1577 component recognition program: 1 5000 V rms isolation voltage VDE To be certified according to DIN EN 60747-5-2 (VDE 0884 Part 2): 2003-01: 2 Basic insulation, 848 V peak Complies with DIN EN 60747-5-2 (VDE 0884 Part 2): 2003-01, DIN EN 60950 (VDE 0805): 2001-12; EN 60950: 2000, reinforced insulation, 560 V peak 1 2 In accordance with UL1577, each ADM2490E is proof tested by applying an insulation test voltage 6000 V rms for 1 second (current leakage detection limit = 10 A). In accordance with DIN EN 60747-5-2, each ADM2490E is proof tested by applying an insulation test voltage 1590 V peak for 1 second (partial discharge detection limit = 5 pC). INSULATION AND SAFETY-RELATED SPECIFICATIONS Table 6. Parameter Rated Dielectric Insulation Voltage Minimum External Air Gap (Clearance) Minimum External Tracking (Creepage) Minimum Internal Gap (Internal Clearance) Tracking Resistance (Comparative Tracking Index) Isolation Group Symbol L(I01) L(I02) Value 5000 7.45 8.1 0.017 >175 IIIa Unit V rms mm min mm min mm min V Conditions 1-minute duration. Measured from input terminals to output terminals, shortest distance through air. Measured from input terminals to output terminals, shortest distance along body. Insulation distance through insulation. DIN IEC 112/VDE 0303 Part 1. Material Group (DIN VDE 0110, 1/89). CTI Rev. 0 | Page 5 of 16 ADM2490E VDE 0884 INSULATION CHARACTERISTICS (PENDING) This isolator is suitable for basic electrical isolation only within the safety limit data. Maintenance of the safety data must be ensured by means of protective circuits. An asterisk (*) on a package denotes VDE 0884 approval for 848 V peak working voltage. Table 7. Description Installation Classification per DIN VDE 0110 for Rated Mains Voltage 300 V rms 450 V rms 600 V rms Climatic Classification Pollution Degree (DIN VDE 0110, see Table 1) Maximum Working Insulation Voltage Input-to-Output Test Voltage, Method b1 VIORM x 1.875 = VPR, 100% Production Tested, tm = 1 sec, Partial Discharge < 5 pC Input-to-Output Test Voltage, Method a (After Environmental Tests, Subgroup 1) VIORM x 1.6 = VPR, tm = 60 sec, Partial Discharge < 5 pC (After Input and/or Safety Test, Subgroup 2/3) VIORM x 1.2 = VPR, tm = 60 sec, Partial Discharge < 5 pC Highest Allowable Overvoltage (Transient Overvoltage, tTR = 10 sec) Safety-Limiting Values (Maximum Value Allowed in the Event of a Failure; see Figure 16) Case Temperature Input Current Output Current Insulation Resistance at TS, VIO = 500 V Symbol Characteristic I to IV I to II I to II 40/105/21 2 848 1590 Unit VIORM VPR VPEAK VPEAK 1357 VPR VTR 1018 6000 VPEAK VPEAK VPEAK TS IS, INPUT IS, OUTPUT RS 150 265 335 >109 C mA mA Rev. 0 | Page 6 of 16 ADM2490E ABSOLUTE MAXIMUM RATINGS TA = 25C, unless otherwise noted. Each voltage is relative to its respective ground. Table 8. Parameter Storage Temperature Ambient Operating Temperature VDD1 VDD2 Logic Input Voltages Bus Terminal Voltages Logic Output Voltages Average Output Current, per Pin ESD (Human Body Model) on A, B, Y, and Z pins JA Thermal Impedance Rating -55C to +150C -40C to +105C -0.5 V to +7 V -0.5 V to +6 V -0.5 V to VDD1 + 0.5 V -9 V to +14 V -0.5 V to VDD1 + 0.5 V 35 mA 8 kV 73C/W Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Absolute maximum ratings apply individually only, not in combination. ESD CAUTION Rev. 0 | Page 7 of 16 ADM2490E PIN CONFIGURATION AND FUNCTIONAL DESCRIPTIONS VDD1 1 GND1 2 RxD 3 NC 4 16 VDD2 15 GND2 14 A 13 B TOP VIEW GND1 5 (Not to Scale) 12 NC TxD 6 11 Z ADM2490E NC 7 GND1 8 10 Y 9 05889-002 GND2 NC = NO CONNECT Figure 2. ADM2490E Pin Configuration Table 9. Pin Function Descriptions Pin No. 1 2, 5, 8 3 4, 7, 12 6 9, 15 16 11 10 13 14 Mnemonic VDD1 GND1 RxD NC TxD GND2 VDD2 Z Y B A Description Power Supply (logic side). Decoupling capacitor to GND1 required; capacitor value should be between 0.01 F and 0.1 F. Ground (logic side). Receiver Output. No Connect. These pins must be left floating. Transmit Data. Ground (bus side). Power Supply (bus side). Decoupling capacitor to GND2 required; capacitor value should be between 0.01 F and 0.1 F. Driver Inverting Output. Driver Noninverting Output. Receiver Inverting Input. Receiver Noninverting Input. Rev. 0 | Page 8 of 16 ADM2490E TEST CIRCUITS RL VOD 05889-003 Y RL CL1 RLDIFF CL2 05889-005 VOC Z Figure 3. Driver Voltage Measurement Figure 6. Driver Propagation Delay 375 A VOD3 60 VTEST 05889-004 B CL 375 Figure 4. Driver Voltage Measurement Figure 7. Receiver Propagation Delay VDD2 VDD1 VDD2 220 100 220 TxD GALVANIC ISOLATION Y Z A B GND2 05889-014 RxD GND1 GND2 Figure 5. Supply-Current Measurement Test Circuit, See Figure 10 and Figure 11 Rev. 0 | Page 9 of 16 05889-006 VOUT ADM2490E SWITCHING CHARACTERISTICS 3V 1.5V 0V 1.5V tPLH Z VO Y 1/2VO tPHL A, B 0V 0V tPLH tPWD = |tPLH - tPHL | tPHL VOH VOH A, B VOL 90% POINT 90% POINT RO 05889-007 1.5V 1.5V 10% POINT tR tF 10% POINT VOL Figure 8. Driver Propagation Delay, Rise/Fall Timing Figure 9. Receiver Propagation Delay Rev. 0 | Page 10 of 16 05889-008 ADM2490E TYPICAL PERFORMANCE CHARACTERISTICS 3.00 60 2.95 50 tPLH tPHL 2.90 DELAY (ns) 40 NO LOAD 100 LOAD 220-100-220 LOAD IDD1 (mA) 2.85 30 2.80 20 2.75 10 05889-015 -20 0 20 40 60 80 100 -20 0 20 40 60 80 100 TEMPERATURE (C) TEMPERATURE (C) Figure 10. IDD1 Supply Current vs. Temperature (See Figure 5) Figure 13. Receiver Propagation Delay vs. Temperature 70 60 220-100-220 LOAD 50 IDD2 (mA) TxD 40 30 20 10 0 -40 1 100 LOAD Y AND Z OUTPUTS 2 RxD NO LOAD 4 05889-019 -20 0 20 40 60 80 100 05889-016 TEMPERATURE (C) CH1 2V CH3 2V CH2 2V CH4 2V M20ns T 44.2% A CH2 2.84V Figure 11. IDD2 Supply Current vs. Temperature (See Figure 5) Figure 14. Driver/Receiver Propagation Delay, Low to High (RLDIFF = 54 , CL1 = CL2 = 100 pF) 60 50 TPZHL TPYLH TPZLH TPYHL 40 DELAY (ns) TxD 1 30 Y AND Z OUTPUTS 20 2 10 4 RxD 05889-020 -20 0 20 40 60 80 100 05889-017 0 -40 TEMPERATURE (C) CH1 2V CH3 2V CH2 2V CH4 2V M20ns T 44.2% A CH2 2.84V Figure 12. Driver Propagation Delay vs. Temperature Figure 15. Driver/Receiver Propagation Delay, High to Low (RLDIFF = 54 , CL1 = CL2 = 100 pF) Rev. 0 | Page 11 of 16 05889-018 2.70 -40 0 -40 ADM2490E 350 300 SAFETY-LIMITING CURRENT (mA) 4.77 4.76 4.75 4.74 250 SIDE 2 200 150 VOLTAGE (V) 4.73 4.72 4.71 4.70 4.69 4.68 4.67 SIDE 1 100 50 0 05889-021 0 50 100 150 CASE TEMPERATURE (C) 200 -20 0 20 40 60 80 100 TEMPERATURE (C) Figure 16. Thermal Derating Curve, Dependence of Safety-Limiting Values with Case Temperature per VDE 0884 Figure 19. Receiver Output High Voltage vs. Temperature, IRxD = -4 mA 0 -2 -4 0.35 0.30 0.25 VOLTAGE (V) CURRENT (mA) -6 -8 -10 -12 -14 4.0 0.20 0.15 0.10 0.05 0 -40 05889-022 4.2 4.4 4.6 4.8 5.0 -20 0 20 40 60 80 100 VOLTAGE (V) TEMPERATURE (C) Figure 17. Output Current vs. Receiver Output High Voltage Figure 20. Receiver Output Low Voltage vs. Temperature, IRxD = -4 mA 16 14 12 CURRENT (mA) 10 8 6 4 2 0 0 0.2 0.4 0.6 VOLTAGE (V) 0.8 1.0 1.2 Figure 18. Output Current vs. Receiver Output Low Voltage Rev. 0 | Page 12 of 16 05889-023 05889-025 05889-024 4.66 -40 ADM2490E CIRCUIT DESCRIPTION ELECTRICAL ISOLATION In the ADM2490E, electrical isolation is implemented on the logic side of the interface. Therefore, the part has two main sections: a digital isolation section and a transceiver section (see Figure 21). The driver input signal, which is applied to the TxD pin and referenced to logic ground (GND1), is coupled across an isolation barrier to appear at the transceiver section referenced to isolated ground (GND2). Similarly, the receiver input, which is referenced to isolated ground in the transceiver section, is coupled across the isolation barrier to appear at the RxD pin referenced to logic ground. TRUTH TABLES The truth tables in this section use the abbreviations shown in Table 10. Table 10. Truth Table Abbreviations Abbreviation H I L X Description High level Indeterminate Low level Irrelevant iCoupler Technology The digital signals are transmitted across the isolation barrier using iCoupler technology. This technique uses chip scale transformer windings to couple the digital signals magnetically from one side of the barrier to the other. Digital inputs are encoded into waveforms that are capable of exciting the primary transformer winding. At the secondary winding, the induced waveforms are decoded into the binary value that was originally transmitted. Table 11. Transmitting VDD1 On On Supply Status VDD2 On On Input TxD H L Outputs Y Z H L L H Table 12. Receiving Supply Status VDD1 VDD2 On On On On On On On On On Off Off On Off Off Inputs A - B (V) >0.2 <-0.2 -0.2 < A - B < +0.2 Inputs open X X X Output RxD H L I H H H L VDD1 ISOLATION BARRIER VDD2 TxD ENCODE DECODE D Y Z RxD DECODE ENCODE R A B DIGITAL ISOLATION TRANSCEIVER 05889-009 GND1 GND2 Figure 21. ADM2490E Digital Isolation and Transceiver Sections Rev. 0 | Page 13 of 16 ADM2490E THERMAL SHUTDOWN MAXIMUM ALLOWABLE MAGNETIC FLUX DENSITY (kGAUSS) 100 The ADM2490E contains thermal-shutdown circuitry that protects the part from excessive power dissipation during fault conditions. Shorting the driver outputs to a low impedance source can result in high driver currents. The thermal sensing circuitry detects the increase in die temperature under this condition and disables the driver outputs. This circuitry is designed to disable the driver outputs when a die temperature of 150C is reached. As the device cools, the drivers are re-enabled at a temperature of 140C. 10 1 0.1 FAIL-SAFE RECEIVER INPUTS The receiver inputs include a fail-safe feature that guarantees a logic high on the RxD pin when the A and B inputs are floating or open-circuited. 0.01 10k 100k 1M 10M MAGNETIC FIELD FREQUENCY (Hz) 100M MAGNETIC FIELD IMMUNITY Because iCouplers use a coreless technology, no magnetic components are present and the problem of magnetic saturation of the core material does not exist. Therefore, iCouplers have essentially infinite dc field immunity. The following analysis defines the conditions under which this may occur. The 3 V operating condition of the ADM2409E is examined because it represents the most susceptible mode of operation. The limitation on the ac magnetic field immunity of the iCoupler is set by the condition that induced an error voltage in the receiving coil (the bottom coil in this case) that was large to either falsely set or reset the decoder. The voltage induced across the bottom coil is given by - d 2 V = rn ; n = 1, 2, . . . , N dt Figure 22. Maximum Allowable External Magnetic Flux Density For example, at a magnetic field frequency of 1 MHz, the maximum allowable magnetic field of 0.2 kGauss induces a voltage of 0.25 V at the receiving coil. This is about 50% of the sensing threshold and does not cause a faulty output transition. Similarly, if such an event occurs during a transmitted pulse and is the worst-case polarity, it reduces the received pulse from >1.0 V to 0.75 V--still well above the 0.5 V sensing threshold of the decoder. Figure 23 shows the magnetic flux density values in terms of more familiar quantities, such as maximum allowable current flow, at given distances away from the ADM2490E transformers. 1000 MAXIMUM ALLOWABLE CURRENT (kA) DISTANCE = 1m 100 DISTANCE = 5mm 10 DISTANCE = 100mm 1 where, if the pulses at the transformer output are greater than 1.0 V in amplitude: = magnetic flux density (gauss). N = number of turns in receiving coil. rn = radius of nth turn in receiving coil (cm). The decoder has a sensing threshold of about 0.5 V; therefore, there is a 0.5 V margin in which induced voltages can be tolerated. Given the geometry of the receiving coil and an imposed requirement that the induced voltage is, at most, 50% of the 0.5 V margin at the decoder, a maximum allowable magnetic field is calculated, as shown in Figure 22. 0.1 10k 100k 1M 10M MAGNETIC FIELD FREQUENCY (Hz) 100M Figure 23. Maximum Allowable Current for Various Current-to-ADM2490E Spacings With combinations of strong magnetic field and high frequency, any loops formed by printed circuit board traces could induce error voltages large enough to trigger the thresholds of succeeding circuitry. Care should be taken in the layout of such traces to avoid this possibility. Rev. 0 | Page 14 of 16 05889-011 0.01 1k 05889-010 0.001 1k ADM2490E APPLICATIONS INFORMATION ISOLATED POWER-SUPPLY CIRCUIT The ADM2490E requires isolated power capable of 5 V at up to approximately 75 mA (this current is dependant on the data rate and termination resistors used) to be supplied between the VDD2 and the GND2 pins. A transformer-driver circuit with a center-tapped transformer and LDO can be used to generate the isolated 5 V supply, as shown in Figure 25. The center-tapped transformer provides electrical isolation of the 5 V power supply. The primary winding of the transformer is excited with a pair of square waveforms that are 180 out of phase with each other. A pair of Schottky diodes and a smoothing capacitor are used to create a rectified signal from the secondary winding. The ADP667 linear voltage regulator provides a regulated power supply to the bus-side circuitry (VDD2) of the ADM2490E. VDD2. The capacitor value should be between 0.01 F and 0.1 F. The total lead length between both ends of the capacitor and the input power-supply pin should not exceed 20 mm. Bypassing between Pins 1 and 8 and between Pins 9 and 16 should also be considered unless the ground pair on each package side is connected close to the package. VDD1 GND1 RxD NC GND1 TxD NC GND1 VDD2 GND2 A B NC Z Y GND2 ADM2490E NC = NO CONNECT Figure 24. Recommended Printed Circuit Board Layout PC BOARD LAYOUT The ADM2490E isolated RS-485 transceiver requires no external interface circuitry for the logic interfaces. Powersupply bypassing is required at the input and output supply pins (Figure 24). Bypass capacitors are conveniently connected between Pins 1 and 2 for VDD1 and between Pins 15 and 16 for In applications involving high common-mode transients, care should be taken to ensure that board coupling across the isolation barrier is minimized. Furthermore, the board layout should be designed such that any coupling that does occur equally affects all pins on a given component side. Failure to ensure this could cause voltage differentials between pins exceeding the absolute maximum ratings of the device, thereby leading to latch-up or permanent damage. VCC ISOLATION BARRIER SD103C IN VCC 22F OUT 5V 10F TRANSFORMER DRIVER 78253 ADP667 SET GND SHDN SD103C VCC VDD1 VDD2 ADM2490E 05889-012 GND1 GND2 Figure 25. Isolated Power-Supply Circuit Rev. 0 | Page 15 of 16 05889-013 ADM2490E OUTLINE DIMENSIONS 10.50 (0.4134) 10.10 (0.3976) 16 9 7.60 (0.2992) 7.40 (0.2913) 1 8 10.65 (0.4193) 10.00 (0.3937) 1.27 (0.0500) BSC 0.30 (0.0118) 0.10 (0.0039) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122) 2.65 (0.1043) 2.35 (0.0925) 0.50 (0.0197) 0.25 (0.0098) 8 0 0.33 (0.0130) 0.20 (0.0079) 45 SEATING PLANE 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-013- AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 26. 16-Lead Standard Small Outline Package [SOIC_W] Wide Body (RW-16) Dimensions shown in millimeters and (inches) ORDERING GUIDE Model ADM2490EBRWZ 1 ADM2490EBRWZ-REEL71 1 Temperature Range -40C to +105C -40C to +105C Package Description 16-Lead Wide Body SOIC_W 16-Lead Wide Body SOIC_W 060606-A Package Option RW-16 RW-16 Z = Pb-free part. (c)2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05889-0-10/06(0) Rev. 0 | Page 16 of 16 |
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