adm2481 Analog Devices, Inc., adm2481 Datasheet

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adm2481

Manufacturer Part Number
adm2481
Description
Half-duplex, Icoupler Isolated Rs-485 Transceiver Adm2481
Manufacturer
Analog Devices, Inc.
Datasheet

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FEATURES
RS-485 transceiver with electrical data isolation
Complies with ANSI TIA/EIA-485-A and ISO 8482: 1987(E)
500 kbps data rate
Slew rate-limited driver outputs
Low power operation: 2.5 mA maximum
Suitable for 5 V or 3.3 V operations (V
High common-mode transient immunity: >25 kV/μs
True fail-safe receiver inputs
Chatter-free power-up/power-down protection
256 nodes on bus
Thermal shutdown protection
Safety and regulatory approvals (pending)
Operating temperature range: −40°C to +85°C
APPLICATIONS
Low power RS-485/RS-422 networks
Isolated interfaces
Building control networks
Multipoint data transmission systems
GENERAL DESCRIPTION
The ADM2481 differential bus transceiver is an integrated,
galvanically isolated component designed for bidirectional data
communication on balanced, multipoint bus transmission lines.
It complies with ANSI EIA/TIA-485-A and ISO 8482: 1987(E).
Using iCoupler® technology from Analog Devices, Inc., the
ADM2481 combines a 3-channel isolator, a three-state diffe-
rential line driver, and a differential input receiver into a single
package. The logic side of the device is powered with either a
5 V or 3 V supply, and the bus side uses a 5 V supply only.
The ADM2481 is slew-limited to reduce reflections with improp-
erly terminated transmission lines. The controlled slew rate
limits the data rate to 500 kbps. The input impedance of the
device is 96 kΩ, allowing up to 256 transceivers on the bus. Its
driver has an active-high enable feature. The driver differential
outputs and receiver differential inputs are connected internally
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.
UL recognition: 2500 V rms for 1 minute per
VDE certificates of conformity (pending)
DIN V VDE V 0884-10 (VDE V 0884-10): 2006-12
V
UL 1577 (pending)
IORM
= 560 V peak
DD1
)
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
to form a differential I/O port. When the driver is disabled or
when V
the bus. An active-high receiver disable feature, which causes
the receiver output to enter a high impedance state, is provided
as well.
The receiver inputs have a true fail-safe feature that ensures a
logic-high receiver output level when the inputs are open or
shorted. This guarantees that the receiver outputs are in a
known state before communication begins and at the point
when communication ends.
Current limiting and thermal shutdown features protect against
output short circuits and bus contention situations that might
cause excessive power dissipation. The part is fully specified
over the industrial temperature range of −40°C to +85°C and is
available in a 16-lead, wide body SOIC package.
Isolated RS-485 Transceiver
DD1
or V
FUNCTIONAL BLOCK DIAGRAM
RxD
TxD
DE
RE
DD2
Half-Duplex, iCoupler
= 0 V, this imposes minimal loading on
GND
V
DD1
©2010 Analog Devices, Inc. All rights reserved.
1
Figure 1.
ADM2481
GND
V
DD2
2
ADM2481
www.analog.com
A
B

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adm2481 Summary of contents

Page 1

... The logic side of the device is powered with either supply, and the bus side uses supply only. The ADM2481 is slew-limited to reduce reflections with improp- erly terminated transmission lines. The controlled slew rate limits the data rate to 500 kbps. The input impedance of the device is 96 kΩ ...

Page 2

... ADM2481 TABLE OF CONTENTS Features .............................................................................................. 1 Applications ....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications ..................................................................................... 3 Timing Specifications .................................................................. 4 Package Characteristics ............................................................... 4 Regulatory Information (Pending) ............................................ 4 Insulation and Safety-Related Specifications ............................ 4 VDE 0884 Insulation Characteristics (Pending) ...................... 5 Absolute Maximum Ratings ............................................................ 6 ESD Caution .................................................................................. 6 Pin Configuration and Function Descriptions ............................. 7 REVISION HISTORY 7/10— ...

Page 3

... DD1 V 0 ±1 I 2.5 DD1 1.3 I 2.0 DD2 1 Rev Page ADM2481 Unit Test Conditions/Comments ∞, see Figure Ω (RS-422), see Figure Ω (RS-485), see Figure − + ≥ 4.75, TEST DD1 see Figure 17 ...

Page 4

... In accordance with UL 1577, each ADM2481 is proof tested by applying an insulation test voltage of ≥ 3000 V rms for 1 second (current leakage detection limit = 5 μA). In accordance with DIN V VDE V 0884-10, each ADM2481 is proof tested by applying an insulation test voltage of ≥ 1050 V peak for 1 second (partial discharge detection limit = 5 pC). ...

Page 5

... Output Current Insulation Resistance 500 Symbol V IORM INPUT I S, OUTPUT R S Rev Page ADM2481 Characteristic Unit III 40/85/21 2 560 V PEAK 1050 V PEAK 896 V PEAK 672 V PEAK 4000 V PEAK 150 °C ...

Page 6

... ADM2481 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. All voltages are relative to A their respective ground. Table 7. Parameter V DD1 V DD2 Digital Input Voltage (DE, RE, TxD) Digital Output Voltage (RxD) Driver Output/Receiver Input Voltage ESD Rating: Contact (Human Body Model) (A, B Pins) ...

Page 7

... Pin A is put into a high impedance state to avoid overloading the bus. Inverting Driver Output/Receiver Input. When the driver is disabled, or when V down, Pin B is put into a high impedance state to avoid overloading the bus. Power Supply (Bus Side). Rev Page DD1 ADM2481 DD1 DD2 powered DD2 ...

Page 8

... ADM2481 TYPICAL PERFORMANCE CHARACTERISTICS 1.6 I _RCVR_ENABLE @ 5.5V DD1 1.4 1.2 1.0 0.8 I _DE_ENABLE @ 5.5V DD2 0.6 0.4 0.2 0 –40 25 TEMPERATURE (°C) Figure 3. Unloaded Supply Current vs. Temperature 120 100 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT VOLTAGE (V) Figure 4. Output Current vs. Driver Output Low Voltage –10 –30 –50 –70 –90 –110 0 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT VOLTAGE (V) Figure 5. Output Current vs. Driver Output High Voltage ...

Page 9

... CH1 5.00V CH3 1.00V Figure 11. Driver/Receiver Propagation Delay, High to Low CH1 5.00V CH3 1.00V Figure 12. Driver/Receiver Propagation Delay, Low to High Rev Page ADM2481 CH2 1.00V M200ns A CH1 3.10V T 1.33600µs CH4 5.00V CH2 1.00V M200ns A CH1 3.10V CH4 5.00V T 360 ...

Page 10

... ADM2481 350 300 250 BUS SIDE 200 150 LOGIC SIDE 100 100 CASE TEMPERATURE (°C) Figure 13. Thermal Derating Curve, Dependence of Safety-Limiting Values with Case Temperature per VDE 0884 0.25 0.50 0.75 1.00 1.25 OUTPUT VOLTAGE (V) Figure 14. Output Current vs. Receiver Output Low Voltage ...

Page 11

... Figure 18. Driver Propagation Delay TEST Rev Page OUT DE IN Figure 19. Driver Enable/Disable OUT Figure 20. Receiver Propagation Delay +1. –1. OUT RE IN Figure 21. Receiver Enable/Disable ADM2481 ...

Page 12

... ADM2481 SWITCHING CHARACTERISTICS V DD1 0.5V 0.5V DD1 0V t PLH B 1/ – SKEW PLH V OH 90% POINT A, B 10% POINT Figure 22. Driver Propagation Delay, Rise/Fall Timing A – PLH RxD 1. – SKEW PLH PHL Figure 23. Receiver Propagation Delay DD1 DE t PHL ...

Page 13

... CIRCUIT DESCRIPTION ELECTRICAL ISOLATION In the ADM2481, 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 26). Driver input and data enable signals, applied to the TxD and DE pins, respectively, and referenced to logic ground ...

Page 14

... Z Z follows defines the conditions under which this might occur The 3 V operating condition of the ADM2481 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 in which the induced error Outputs ...

Page 15

... V to 0.75 V. This is well above the 0.5 V sensing threshold of the decoder. These magnetic flux density values are shown in Figure 28, using more familiar quantities such as maximum allowable current flow, at given distances away from the ADM2481 transformers. 1000.00 100.00 DISTANCE = 5mm 10 ...

Page 16

... Failure to ensure this can cause voltage differentials between pins that exceed the absolute maximum ratings of the device, thereby leading to latch-up or permanent damage. ISOLATED POWER SUPPLY CIRCUIT The ADM2481 requires isolated power capable 100 supplied between the V no suitable integrated power supply is available, a discrete V DD2 circuit, such as the one in Figure 30, can be used ...

Page 17

... Figure 31. 16-Lead Standard Small Outline Package [SOIC_W] Wide Body (RW-16) Dimensions shown in millimeters and (inches) Temperature Range Package Description −40°C to +85°C 16-Lead, Wide Body SOIC_W −40°C to +85°C 16-Lead, Wide Body SOIC_W Rev Page ADM2481 45° 1.27 (0.0500) 0.40 (0.0157) Package Option RW-16 RW-16 ...

Page 18

... ADM2481 NOTES Rev Page ...

Page 19

... NOTES Rev Page ADM2481 ...

Page 20

... ADM2481 NOTES ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08920-0-7/10(0) Rev Page ...

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