16 Mbps, ESD Protected,
Full-Duplex RS-485 Transceivers
Data Sheet
ADM1490E/ADM1491E
Rev. D
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 ©2008–2012 Analog Devices, Inc. All rights reserved.
FEATURES
RS-485/RS-422 full-duplex transceiver for high speed
motor control applications
16 Mbps data rate
±8 kV ESD protection on RS-485 input/output pins
Complies with ANSI/TIA/EIA-485-A-1998
Open circuit fail-safe
Suitable for 5 V power supply applications
32 nodes on the bus (1 unit load)
Thermal shutdown protection
Operating temperature range: −40°C to +85°C
ADM1490E packages
Narrow body, 8-lead SOIC
8-lead MSOP
ADM1491E packages
Narrow-body, 14-lead SOIC
10-lead MSOP
APPLICATIONS
RS-485/RS-422 interfaces
Industrial field networks
High data rate motor control
Multipoint data transmission systems
Single-ended-to-differential signal conversion
FUNCTIONAL BLOCK DIAGRAMS
ADM1490E
RO
DI
A
B
Z
Y
VCC
GND
R
D
07430-001
Figure 1.
ADM1491E
RO
RE
DE
DI
A
B
Z
Y
GND
R
D
VCC
07430-002
Figure 2.
GENERAL DESCRIPTION
The ADM1490E/ADM1491E are RS-485/RS-422 transceivers
with ±8 kV ESD protection and are suitable for high speed, full-
duplex communication on multipoint transmission lines. In
particular, the ADM1490E/ADM1491E are designed for use in
motor control applications requiring communications at data
rates up to 16 Mbps.
The ADM1490E/ADM1491E are designed for balanced trans-
mission lines and comply with TIA/EIA-485-A-98. The devices
each have a 12 kΩ receiver input impedance for unit load RS-485
operation, allowing up to 32 nodes on the bus.
The differential transmitter outputs and receiver inputs feature
electrostatic discharge circuitry that provides protection to ±8 kV
using the human body model (HBM).
The ADM1490E/ADM1491E operate from a single 5 V power
supply. Excessive power dissipation caused by bus contention
or output shorting is prevented by short-circuit protection and
thermal circuitry. Short-circuit protection circuits limit the
maximum output current to ±250 mA during fault conditions.
A thermal shutdown circuit senses if the die temperature rises
above 150°C and forces the driver outputs into a high impedance
state under this condition.
The receiver of the ADM1490E/ADM1491E contains a fail-safe
feature that results in a logic high output state if the inputs are
unconnected (floating).
The ADM1490E/ADM1491E feature extremely fast and closely
matched switching times. Minimal driver propagation delays
permit transmission at data rates up to 16 Mbps, and low skew
minimizes EMI interference.
The ADM1490E/ADM1491E are fully specified over the
commercial and industrial temperature ranges. The ADM1490E
is available in two packages: a narrow body, 8-lead SOIC and an
8-lead MSOP. The ADM1491E is also available in two packages:
a narrow body, 14-lead SOIC and a 10-lead MSOP.
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 2 of 16
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Functional Block Diagrams ............................................................. 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Timing Specifications .................................................................. 4
Absolute Maximum Ratings ............................................................ 5
Thermal Resistance ...................................................................... 5
ESD Caution .................................................................................. 5
Pin Configurations and Function Descriptions ........................... 6
Typical Performance Characteristics ..............................................7
Test Circuits ........................................................................................9
Theory of Operation ...................................................................... 10
Truth Tables................................................................................. 10
ESD Transient Protection Scheme ........................................... 10
Applications Information .............................................................. 12
Differential Data ......................................................................... 12
Cable and Data Rate ................................................................... 12
Typical Applications ................................................................... 12
Outline Dimensions ....................................................................... 14
Ordering Guide .......................................................................... 15
REVISION HISTORY
2/12—Rev. C to Rev. D
Changes to Figure 8 .......................................................................... 6
Updated Outline Dimensions ....................................................... 14
12/10—Rev. B to Rev. C
Changes to Figure 29 ...................................................................... 12
Changes to Figure 30 ...................................................................... 13
7/09—Rev. A to Rev. B
Added ADM1490E, 8-Lead SOIC, and 8-Lead MSOP .... Universal
Changes to Table 4 ............................................................................ 5
Added Figure 7; Renumbered Figures Sequentially ..................... 6
Changes to Table 5 ............................................................................ 6
Changes to Typical Applications Section .................................... 12
Added Figure 29 .............................................................................. 12
Changes to Figure 30 ...................................................................... 13
Updated Outline Dimensions ....................................................... 14
Changes to Ordering Guide .......................................................... 15
2/09—Rev. 0 to Rev. A
Change to Table 9 ........................................................................... 11
12/08—Revision 0: Initial Version
Data Sheet ADM1490E/ADM1491E
Rev. D | Page 3 of 16
SPECIFICATIONS
4.75 V ≤ VCC ≤ 5.25 V; all minimum/maximum specifications apply over the entire recommended operation range, unless otherwise
noted. All typical specifications are at TA = 25°C, VCC = 5.0 V, unless otherwise noted.
Table 1.
Parameter Symbol Min Typ Max Unit Test Conditions/Comments
SUPPLY CURRENT
Outputs Enabled ICC1 1.2 2.0 mA Outputs unloaded, digital inputs = VCC or GND
Outputs Disabled ICC2 0.8 1.5 mA Outputs unloaded, digital inputs = VCC or GND
DRIVER
Differential Outputs
Differential Output Voltage, Loaded |VOD2| 2.0 5.0 V RL = 100 Ω (RS-422), see Figure 21
1.5 5.0 V RL = 54 Ω (RS-485), see Figure 21
|VOD3| 1.5 5.0 V −7 V ≤ VTEST ≤ +12 V, see Figure 22
∆|VOD| for Complementary Output States ∆|VOD2| 0.2 V RL = 54 Ω or 100 Ω, see Figure 21
Common-Mode Output Voltage VOC 3.0 V RL = 54 Ω or 100 Ω, see Figure 21
∆|VOC| for Complementary Output States ∆|VOC| 0.2 V RL = 54 Ω or 100 Ω, see Figure 21
Output Leakage Current (Y, Z) IO 100 µA DE = 0 V, VDD = 0 V or 5 V, VIN = 12 V
IO −100 µA DE = 0 V, VDD = 0 V or 5 V, VIN = −7 V
Output Short-Circuit Current IOS 250 mA −7 V < VOUT < +12 V
Logic Inputs DE,
RE
, DI
Input Low Voltage VIL 0.8 V DE, RE, DI
Input High Voltage VIH 2.0 V DE, RE, DI
Input Current II −1 +1 µA DE, RE, DI
RECEIVER
Differential Inputs
Differential Input Threshold Voltage VTH −0.2 +0.2 V −7 V < VCM < +12 V
Input Voltage Hysteresis VHYS 30 mV VCM = 0 V
Input Current (A, B)
I
I
1.0
mA
V
CM
= 12 V
−0.8 mA VCM = −7 V
Line Input Resistance RIN 12 30 kΩ −7 V ≤ VCM ≤ +12 V
Logic Outputs
Output Voltage Low VOL 0.4 V IOUT = +4.0 mA, VA − VB = −0.2 V
Output Voltage High VOH 4.0 V IOUT = −4.0 mA, VA − VB = +0.2 V
Short-Circuit Current 85 mA
Three-State Output Leakage Current IOZR ±1 µA VCC = 5.25 V, 0.4 V < VOUT < 2.4 V
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 4 of 16
TIMING SPECIFICATIONS
TA = −40°C to +85°C.
Table 2.
Parameter Symbol Min Typ Max Unit Test Conditions/Comments
DRIVER
Maximum Data Rate 16 Mbps
Propagation Delay tDPLH, tDPHL 11 17 ns RL = 54 Ω, CL = 100 pF, see Figure 23 and Figure 3
Driver Output Skew tSKEW 0.5 2 ns RL = 54 Ω, CL = 100 pF, see Figure 23 and Figure 3,
tSKEW = |tDPLH − tDPHL|
Rise Time/Fall Time
t
DR
, t
DF
8
15
ns
R
L
= 54 Ω, C
L
= 100 pF, see Figure 23 and Figure 3
Enable Time tZH, tZL 20 ns RL = 110 Ω, CL = 50 pF, see Figure 24 and Figure 5
Disable Time tHZ, tLZ 20 ns RL = 110 Ω, CL = 50 pF, see Figure 24 and Figure 5
RECEIVER
Propagation Delay tPLH, tPHL 12 20 ns CL = 15 pF, see Figure 25 and Figure 4
Skew |tPLH − tPHL| tSKEW 0.4 2 ns CL = 15 pF, see Figure 25 and Figure 4
Enable Time tZH, tZL 13 ns RL = 1 kΩ, CL = 15 pF, see Figure 26 and Figure 6
Disable Time tHZ, tLZ 13 ns RL = 1 kΩ, CL = 15 pF, see Figure 26 and Figure 6
Timing Diagrams
Switching Characteristics
Z
Y
V
CC
/2 V
CC
/2
tDPLH tDPHL
1/2V
O
V
O
90% PO INT
10% PO INT 10% PO INT
90% PO INT
V
DIFF
= V
(Y)
– V
(Z)
tDR tDF
–V
O
V
DIFF
+V
O
0V
V
CC
07430-009
Figure 3. Driver Propagation Delay Rise/Fall Timing
A – B
RO
0V 0V
1.5V 1.5V
V
OH
V
OL
t
PLH
t
PHL
t
SKEW
= |
t
PLH
–
t
PHL
|
07430-010
Figure 4. Receiver Propagation Delay Timing
DE
Y, Z
Y, Z
V
CC
0V
0V
V
OL
V
OH
0.5V
CC
0.5V
CC
t
ZL
t
LZ
t
ZH
t
HZ
V
OL
+ 0.5V
V
OH
– 0.5V
2.3V
2.3V
07430-011
Figure 5. Driver Enable/Disable Timing
OUTPUT LOW
OUTPUT HIGH
1.5V
1.5V
RO
RO
RE
0V
0.7V
CC
0.3V
CC
V
OL
V
OH
0.5V
CC
0.5V
CC
t
ZL
t
LZ
t
ZH
t
HZ
V
OL
+ 0.5V
V
OH
– 0.5V
07430-012
Figure 6. Receiver Enable/Disable Timing
Data Sheet ADM1490E/ADM1491E
Rev. D | Page 5 of 16
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 3.
Parameter Rating
VCC to GND −0.3 V to +7 V
Digital I/O Voltage (DE, RE) −0.3 V to VCC + 0.3 V
Driver Input Voltage (DI) −0.3 V to VCC + 0.3 V
Receiver Output Voltage (RO) −0.3 V to VCC + 0.3 V
Driver Output/Receiver Input Voltage
(A, B, Y, Z)
−9 V to +14 V
Operating Temperature Range −40°C to +85°C
Storage Temperature Range −55°C to +150°C
ESD (HBM) on A, B, Y, and Z ±8 kV
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.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 4. Thermal Resistance
Package Type θJA Unit
8-Lead SOIC 121 °C/W
14-Lead SOIC
86
°C/W
8-Lead MSOP
133
°C/W
10-Lead MSOP 133 °C/W
ESD CAUTION
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 6 of 16
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
07430-034
V
CC 1
RO
2
DI
3
GND
4
A
8
B
7
Z
6
Y
5
ADM1490E
TOP VIEW
(Not to Scale)
Figure 7. 8-Lead MSOP and 8-Lead SOIC
Pin Configuration
07430-013
NOTES
1. NC = NO CONNECT. DO NO T CONNE CT
TO THIS PIN.
2. PI N 7 IS NO T CONNE CTED INTE RNALLY .
SHOWN AS GND TO COMPLY WITH
INDUS TRY STANDARD PI NOUT .
3. PI N 14 IS NO T CONNE CTED INTE RNALLY .
SHO WN AS VCC TO COMPLY WITH
INDUS TRY STANDARD PI NOUT .
NC 1
RO 2
RE 3
DE 4
VCC
14
VCC
13
A
12
B
11
DI 5Z
10
GND 6Y
9
GND 7NC
8
ADM1491E
TOP VIEW
(No t t o Scal e)
Figure 8. 14-Lead, Narrow Body SOIC
Pin Configuration
RO
1
RE
2
DE 3
DI 4
GND 5
VCC
10
A
9
B
8
Z
7
Y
6
ADM1491E
TOP VIEW
(Not t o Scale)
07430-015
Figure 9. 10-Lead MSOP
Pin Configuration
Table 5. Pin Function Descriptions
Pin No.
Mnemonic Description
8-Lead SOIC,
8-Lead MSOP 14-Lead SOIC 10-Lead MSOP
N/A1 1 N/A1 NC No Connect. This pin is available on the 14-lead SOIC only.
2 2 1 RO Receiver Output.
N/A1 3 2 RE Receiver Output Enable. A low level enables the receiver output, whereas
a high level places the receiver output in a high impedance state.
N/A1 4 3 DE Driver Output Enable. A logic high enables the differential driver outputs,
A and B, whereas a logic low places the differential driver outputs in a
high impedance state.
3 5 4 DI Driver Input. When the driver is enabled, a logic low on DI forces Pin A low
and Pin B high, whereas a logic high on DI forces Pin A high and Pin B low.
4 6 5 GND Ground.
N/A1 7 N/A1 GND Ground. This pin is available on the 14-lead SOIC only.
N/A1 8 N/A1 NC No Connect. This pin is available on the 14-lead SOIC only.
5 9 6 Y Noninverting Driver Output Y.
6 10 7 Z Inverting Driver Output Z.
7 11 8 B Inverting Receiver Input B.
8 12 9 A Noninverting Receiver Input A.
1
13
10
V
CC
Power Supply (5 V ± 5%).
N/A1 14 N/A1 VCC Power Supply (5 V ± 5%). This pin is available on the 14-lead SOIC only.
1 N/A indicates not applicable.
Data Sheet ADM1490E/ADM1491E
Rev. D | Page 7 of 16
TYPICAL PERFORMANCE CHARACTERISTICS
OUTPUT VOLTAGE (V)
OUTPUT CURRE NT (mA)
35
30
25
20
10
15
0
5
00.500.25 1.000.75 1.50 1.751.25 2.00
07430-016
Figure 10. Output Current vs. Receiver Output Low Voltage
OUTPUT VOLTAGE (V)
OUTPUT CURRE NT (mA)
0
–5
–10
–20
–15
–30
–25
3.50 3.75 4.254.00 4.50 4.75 5.00
07430-017
Figure 11. Output Current vs. Receiver Output High Voltage
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
4.75
4.70
4.60
4.65
4.50
4.55
–50 –25 5025075 85
07430-018
Figure 12. Receiver Output High Voltage vs. Temperature (IOUT = 8 mA)
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
0.50
0.45
0.25
0.40
0.35
0.30
0.15
0.20
–50 –25 5025075 85
07430-019
Figure 13. Receiver Output Low Voltage vs. Temperature (IOUT = 8 mA)
OUTPUT VOLTAGE (V)
OUTPUT CURRE NT (mA)
80
70
20
60
50
30
40
–10
0
10
00.5 2.52.01.51.0 3.53.0 4.0 4.5
07430-020
Figure 14. Output Current vs. Driver Differential Output Voltage
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
3.00
2.95
2.75
2.90
2.80
2.85
2.60
2.65
2.70
–50 250–25 7550 85
07430-021
Figure 15. Driver Differential Output Voltage vs. Temperature (RL = 56.3 Ω)
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 8 of 16
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
80
70
30
60
40
50
0
10
20
01.51.00.5 2.52.0 3.53.0 4.0
07430-022
Figure 16. Output Current vs. Driver Output Low Voltage
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
0
–10
–50
–20
–40
–30
–80
–70
–60
01.51.00.5 3.02.52.0 4.54.03.5 5.0
07430-023
Figure 17. Output Current vs. Driver Output High Voltage
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
1.30
1.25
1.00
1.20
1.05
1.10
1.15
0.80
0.85
0.90
0.95
–50 –25 2507550 85
07430-024
DRIVER ENABLED
DRIVER DISABLED
Figure 18. Output Current vs. Temperature
07430-032
CH3 2V
CH2 2VCH1 5V M200ns A CH1 1.6V
3
1
Figure 19. Unloaded Driver Differential Outputs
07430-033
CH3 2V
CH2 2VCH1 5V M200ns A CH1 1.6V
3
1
Figure 20. Loaded Driver Differential Outputs
(RL Differential = 54 Ω, CL = 100 pF)
Data Sheet ADM1490E/ADM1491E
Rev. D | Page 9 of 16
TEST CIRCUITS
Y
Z
DI
V
OD2
V
OC
R
L
2
R
L
2
07430-003
Figure 21. Driver Voltage Measurements
Y
Z
DI
V
OD3
V
TEST
375Ω
375Ω
60Ω
07430-004
Figure 22. Driver Voltage Measurements
Y
Z
DI R
L
C
L
C
L
07430-005
Figure 23. Driver Propagation Delay
Y
Z
DI
DE
S1 S2
VOUT VCC
RL
110Ω
CL
50pF
07430-006
Figure 24. Driver Enable/Disable Timing
C
L
V
OUT
RE
A
B
07430-007
Figure 25. Receiver Propagation Delay
VCC
S2
+1.5V
–1.5V
S1
RE
RE
C
L
RL
VOUT
07430-008
Figure 26. Receiver Enable/Disable Timing
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 10 of 16
THEORY OF OPERATION
The ADM1490E/ADM1491E are RS-422/RS-485 transceivers that
operate from a single 5 V ± 5% power supply. The ADM1490E/
ADM1491E are intended for balanced data transmission and
comply with both TIA/EIA-485-A and TIA/EIA-422-B. Each
device contains a differential line driver and a differential line
receiver and is suitable for full-duplex data transmission.
The input impedance of the ADM1490E/ADM1491E is 12 kΩ,
allowing up to 32 transceivers on the differential bus. A thermal
shutdown circuit prevents excessive power dissipation caused by
bus contention or by output shorting. This feature forces the driver
output into a high impedance state if, during fault conditions,
a significant temperature increase is detected in the internal
driver circuitry.
The receiver contains a fail-safe feature that results in a logic
high output state if the inputs are unconnected (floating).
The ADM1490E/ADM1491E feature very low propagation delay,
ensuring maximum baud rate operation. The balanced driver
ensures distortion-free transmission.
Another important specification is a measure of the skew between
the complementary outputs. Excessive skew impairs the noise
immunity of the system and increases the amount of electro-
magnetic interference (EMI).
TRUTH TABLES
Table 6. Abbreviations in Truth Tables
Letter Description
H High level
I Indeterminate
L Low level
X Irrelevant
Z High impedance (off)
Table 7. Transmitting
Inputs Outputs
DE DI Z Y
H
H
L
H
H L H L
L X Z Z
Table 8. Receiving
Inputs Output
RE A − B RO
L ≥ +0.2 V H
L ≤ −0.2 V L
L −0.2 V ≤ A − B ≤ +0.2 V I
L Inputs open H
H X Z
ESD TRANSIENT PROTECTION SCHEME
The ADM1490E/ADM1491E use protective clamping
structures on their inputs and outputs to clamp the voltage to a
safe level and dissipate the energy present in ESD (electrostatic).
The protection structure achieves ESD protection up to ±8 kV
human body model (HBM).
ESD Testing
Two coupling methods are used for ESD testing: contact dis-
charge and air gap discharge. Contact discharge calls for a direct
connection to the unit being tested; air gap discharge uses a higher
test voltage but does not make direct contact with the unit under
test. With air discharge, the discharge gun is moved toward the
unit under test, developing an arc across the air gap; therefore,
the term air discharge. This method is influenced by humidity,
temperature, barometric pressure, distance, and rate of closure
of the discharge gun. The contact discharge method, though
less realistic, is more repeatable and is gaining acceptance and
preference over the air gap method.
Although very little energy is contained within an ESD pulse,
the extremely fast rise time, coupled with high voltages, can cause
failures in unprotected semiconductors. Catastrophic destruction
can occur immediately because of arcing or heating. Even if cata-
strophic failure does not occur immediately, the device can suffer
from parametric degradation, resulting in degraded performance.
The cumulative effects of continuous exposure can eventually
lead to complete failure.
07430-025
C1
R2
HIGH
VOLTAGE
GENERATOR DEVICE
UNDER TE S T
NOTES
1. THE ESD TEST METHOD USED IS THE
HUMAN BODY MODEL (±8kV) WITH
R2 = 1500Ω AND C1 = 100pF.
Figure 27. ESD Generator
I/O lines are particularly vulnerable to ESD damage. Simply
touching or plugging in an I/O cable may result in a static dis-
charge that can damage or destroy the interface product connected
to the I/O port. It is, therefore, extremely important to have high
levels of ESD protection on the I/O lines.
The ESD discharge can induce latch-up in the device under test.
Therefore, it is important to conduct ESD testing on the I/O pins
while power is applied to the device. This type of testing is more
representative of a real-world I/O discharge in which the equip-
ment is operating normally when the discharge occurs.
Data Sheet ADM1490E/ADM1491E
Rev. D | Page 11 of 16
100%
90%
36.8%
10%
TIME (
t
)
I
PEAK
t
RL
t
DL
07430-026
Figure 28. Human Body Model ESD Current Waveform
Table 9. ADM1490E/ADM1491E ESD Test Results
ESD Test Method Input/Output Pins Other Pins
Human Body Model ±8 kV ±4 kV
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 12 of 16
APPLICATIONS INFORMATION
DIFFERENTIAL DATA
Differential data transmission reliably transmits data at high
rates over long distances and through noisy environments.
Differential transmission nullifies the effects of ground shifts
and noise signals that appear as common-mode voltages on the
line. There are two main standards approved by the Electronics
Industries Association (EIA) that specify the electrical char-
acteristics of transceivers used in differential data transmission.
The RS-422 standard specifies data rates of up to 10 MBaud and
line lengths of up to 4000 feet. A single driver can drive a trans-
mission line with as many as 10 receivers.
The RS-485 standard addresses true multipoint communications.
This standard meets or exceeds all of the requirements of RS-422,
and it allows as many as 32 drivers and 32 receivers to connect
to a single bus. An extended common-mode range of −7 V to
+12 V is defined. The most significant difference between the
RS-422 and the RS-485 is that the drivers with RS-485 can be
disabled, allowing more than one driver to be connected to a
single line, with as many as 32 drivers connected to a single line.
Only one driver should be enabled at a time, but the RS-485
standard contains additional specifications to guarantee device
safety in the event of line contention.
CABLE AND DATA RATE
Twisted pair is the transmission line of choice for RS-485
communications. Twisted pair cable tends to cancel common-
mode noise and causes cancellation of the magnetic fields
generated by the current flowing through each wire, thereby
reducing the effective inductance of the pair.
An RS-485 transmission line can have as many as 32 trans-
ceivers on the bus. Only one driver can transmit at a time, but
multiple receivers may be enabled simultaneously.
As with any transmission line, it is important to minimize
reflections. This can be achieved by terminating the extreme
ends of the line using resistors equal to the characteristic
impedance of the line. Keep stub lengths of the main line as
short as possible. A properly terminated transmission line
appears purely resistive to the driver.
TYPICAL APPLICATIONS
Figure 29 shows a typical configuration for a full-duplex point-
to-point application using the ADM1490E. Figure 30 shows a
typical configuration for a full-duplex multipoint application
using the ADM1491E. To minimize reflections, the lines must
be terminated at the receiving end in its characteristic impedance,
and stub lengths off the main line must be kept as short as possible.
R
D
RO
DI
ADM1490E
A
B
Z
YR
D
RO
DI
ADM1490E
A
B
Z
Y
NOTES
1. M AX IMUM NUM BE R OF NODES = 32.
07430-027
V
CC
V
CC
GND GND
V
CC
V
CC
R
T
R
T
Figure 29. Typical Point-to-Point Full-Duplex Application
Data Sheet ADM1490E/ADM1491E
Rev. D | Page 13 of 16
R
D
RO
RE
DI
DE
ADM1491E
ADM1491E
A
B
Z
Y
RD
RO DIDE
A B Z Y
RE
R
D
RO
DI
DE
ADM1491E
MASTER SLAVE
SLAVE
A
B
Z
Y
RE
MAXIMUM NUM BE R OF NODES = 32
ADM1491E
RD
RO DIDE
AB Z Y
RE
SLAVE
NOTES
1. R
T
IS E QUAL TO THE CHARACTERI S TIC IMP E DANCE OF THE CABL E .
R
T
07430-028
V
CC
V
CC
R
T
Figure 30. Typical RS-485 Full-Duplex Application
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 14 of 16
OUTLINE DIMENSIONS
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.
COMPLIANT TO JEDEC STANDARDS MS-012-AB
060606-A
14 8
7
1
6.20 (0.2441)
5.80 (0.2283)
4.00 (0.1575)
3.80 (0.1496)
8.75 (0.3445)
8.55 (0.3366)
1.27 (0.0500)
BSC
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0039)
0.51 (0.0201)
0.31 (0.0122)
1.75 (0.0689)
1.35 (0.0531)
0.50 (0.0197)
0.25 (0.0098)
1.27 (0.0500)
0.40 (0.0157)
0.25 (0.0098)
0.17 (0.0067)
COPLANARITY
0.10
8°
0°
45°
Figure 31. 14-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-14)
Dimensions shown in millimeters and (inches)
COMPLIANT TO JEDEC STANDARDS MO-187-BA
091709-A
6°
0°
0.70
0.55
0.40
5
10
1
6
0.50 BSC
0.30
0.15
1.10 MAX
3.10
3.00
2.90
COPLANARITY
0.10
0.23
0.13
3.10
3.00
2.90
5.15
4.90
4.65
PIN 1
IDENTIFIER
15° MAX
0.95
0.85
0.75
0.15
0.05
Figure 32. 10-Lead Mini Small Outline Package [MSOP]
(RM-10)
Dimensions shown in millimeters
Data Sheet ADM1490E/ADM1491E
Rev. D | Page 15 of 16
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.
COMPLIANT TO JEDEC STANDARDS MS-012-AA
012407-A
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
0.50 (0.0196)
0.25 (0.0099) 45°
8°
0°
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0040)
4
1
85
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
1.27 (0.0500)
BSC
6.20 (0.2441)
5.80 (0.2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
Figure 33. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
COMPLIANT TO JEDEC STANDARDS MO-187-AA
6°
0°
0.80
0.55
0.40
4
8
1
5
0.65 BSC
0.40
0.25
1.10 MAX
3.20
3.00
2.80
COPLANARITY
0.10
0.23
0.09
3.20
3.00
2.80
5.15
4.90
4.65
PIN 1
IDENTIFIER
15° MAX
0.95
0.85
0.75
0.15
0.05
10-07-2009-B
Figure 34. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
Temperature
Range Package Description
Package
Option Branding
ADM1490EBRZ −40°C to +85°C 8-Lead Standard Small Outline Package, Narrow Body [SOIC_N] R-8
ADM1490EBRZ-REEL7 −40°C to +85°C 8-Lead Standard Small Outline Package, Narrow Body [SOIC_N] R-8
ADM1490EBRMZ −40°C to +85°C 8-Lead Mini Small Outline Package [MSOP] RM-8 F0E
ADM1490EBRMZ-REEL7 −40°C to +85°C 8-Lead Mini Small Outline Package [MSOP] RM-8 F0E
ADM1491EBRZ −40°C to +85°C 14-Lead Standard Small Outline Package, Narrow Body [SOIC_N] R-14
ADM1491EBRZ-REEL7 −40°C to +85°C 14-Lead Standard Small Outline Package, Narrow Body [SOIC_N] R-14
ADM1491EBRMZ −40°C to +85°C 10-Lead Mini Small Outline Package [MSOP] RM-10 F0D
ADM1491EBRMZ-REEL7 −40°C to +85°C 10-Lead Mini Small Outline Package [MSOP] RM-10 F0D
1 Z = RoHS Compliant Part.
ADM1490E/ADM1491E Data Sheet
Rev. D | Page 16 of 16
NOTES
©2008–2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D07430-0-2/12(D)
