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ADM2481 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADM2481
Beschreibung Isolated RS-485 Transceiver
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 21 Seiten
ADM2481 Datasheet, Funktion
Data Sheet
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 (VDD1)
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
UL recognition: 2500 V rms for 1 minute per
UL 1577
VDE certificates of conformity
DIN V VDE V 0884-10 (VDE V 0884-10): 2006-12
VIORM = 560 V peak
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
Half-Duplex, iCoupler
Isolated RS-485 Transceiver
ADM2481
FUNCTIONAL BLOCK DIAGRAM
VDD1
VDD2
ADM2481
DE
TxD
RxD
RE
GND1
GND2
Figure 1.
A
B
to form a differential I/O port. When the driver is disabled or
when VDD1 or VDD2 = 0 V, this imposes minimal loading on
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.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor 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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
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 ©2010–2012 Analog Devices, Inc. All rights reserved.






ADM2481 Datasheet, Funktion
Data Sheet
ADM2481
VDE 0884 INSULATION CHARACTERISTICS
This isolator is suitable for basic electrical isolation only within this safety limit data. Maintenance of this safety data shall be ensured by
means of protective circuits.
Table 6.
Description
Installation Classification per DIN VDE 0110 for Rated Mains Voltage
≤150 V rms
≤300 V rms
≤400 V rms
Climatic Classification
Pollution Degree (Table 1 in DIN VDE 0110)
Maximum Working Insulation Voltage
Input to Output Test Voltage, Method b1
VIORM × 1.875 = VPR, 100% Production Tested
tm = 1 sec, Partial Discharge of < 5 pC
Input-to-Output Test Voltage, Method a
(After Environmental Tests, Subgroup 1)
VIORM × 1.6 = VPR, tm = 60 sec, Partial Discharge of < 5 pC
(After Input and/or Safety Test, Subgroup 2/3)
VIORM × 1.2 = VPR, tm = 60 sec, Partial Discharge of < 5 pC
Highest Allowable Overvoltage
(Transient Overvoltage, tTR = 10 sec)
Safety-Limiting Values (Maximum Value Allowed in the Event of a Failure; see Figure 13)
Case Temperature
Input Current
Output Current
Insulation Resistance at TS, VIO = 500 V
Symbol
VIORM
VPR
VPR
VTR
TS
IS, INPUT
IS, OUTPUT
RS
Characteristic Unit
I to IV
I to III
I to II
40/85/21
2
560
1050
VPEAK
VPEAK
896
672
4000
150
265
335
>109
VPEAK
VPEAK
VPEAK
°C
mA
mA
Rev. A | Page 5 of 20

6 Page









ADM2481 pdf, datenblatt
Data Sheet
TEST CIRCUITS
VOD
RL
RL
VOC
Figure 16. Driver Voltage Measurement
ADM2481
0V OR 3V
DE IN
A
DE
B
S1
RL
CL
VOUT
Figure 19. Driver Enable/Disable
VCC
S2
375
VOD3
60
375
VTEST
Figure 17. Driver Voltage Measurement over Common-Mode Range
A
B RE
VOUT
CL
Figure 20. Receiver Propagation Delay
A
RL
B
CL1
CL2
Figure 18. Driver Propagation Delay
+1.5V
–1.5V
S1
RE IN
RL
RE
CL
VOUT
Figure 21. Receiver Enable/Disable
VCC
S2
Rev. A | Page 11 of 20

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