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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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