ANALOG DEVICES ADM3485E Service Manual
±15 kV ESD-Protected, 3.3 V,12 Mbps,
www.BDTIC.com/ADI
FEATURES
TIA/EIA RS-485/RS-422 compliant
±15 kV ESD protection on RS-485 input/output pins
12 Mbps data rate
Half-duplex transceiver
Up to 32 nodes on the bus
Receiver open-circuit, fail-safe design
Low power shutdown current
Outputs high-Z when disabled or powered off
Common-mode input range: −7 V to +12 V
Thermal shutdown and short-circuit protection
Industry-standard 75176 pinout
8-lead narrow SOIC package
APPLICATIONS
Power/energy metering
Telecommunications
EMI-sensitive systems
Industrial control
Local area networks
EIA RS-485/RS-422 Transceiver
ADM3485E
FUNCTIONAL BLOCK DIAGRAM
ADM3485E
RO
RE
DE
DI
R
D
Figure 1.
B
A
03338-001
GENERAL DESCRIPTION
The ADM3485E is a 3.3 V, low power data transceiver with
±15 kV ESD protection, suitable for half-duplex communication on multipoint bus transmission lines. The ADM3485E is
designed for balanced data transmission and complies with
TIA/EIA standards RS485 and RS-422. The ADM3485E is
a half-duplex transceiver that shares differential lines and
has separate enable inputs for the driver and the receiver.
The devices have a 12 kΩ receiver input impedance,
h allows up to 32 transceivers on a bus. Because only
whic
one driver should be enabled at any time, the output of a
disabled or powered-down driver is tristated to avoid
overloading the bus.
The receiver has a fail-safe feature that ensures a logic high
o
utput when the inputs are floating. Excessive power dissipation
caused by bus contention or by output shorting is prevented
with a thermal shutdown circuit.
The part is fully specified over the industrial temperature range
a
nd is available in an 8-lead narrow SOIC package.
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her
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 ©2006 Analog Devices, Inc. All rights reserved.
ADM3485E
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TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Timing Specifications....................................................................... 4
Absolute Maximum Ratings............................................................ 5
Thermal Resistance ...................................................................... 5
ESD Caution.................................................................................. 5
Pin Configuration and Pin Function Descriptions...................... 6
REVISION HISTORY
12/06—Rev. B to Rev. C
Updated Format..................................................................Universal
Removed PDIP Model ....................................................... Universal
Changes to Features, Applications, and General Description .... 1
Changes to Specifications................................................................ 3
Changes to Timing Specifications.................................................. 4
Changes to Absolute Maximum Ratings....................................... 5
Reorganized Test Circuits and Switching
C
haracteristics Section..................................................................... 7
Replaced Figure 3 to Figure 11 ....................................................... 7
Deleted Figure 12 to Figure 14........................................................ 8
Changes to Figure 15 to Figure 20.................................................. 9
Changes to Figure 21 and Figure 22............................................. 10
Changes to Table 9.......................................................................... 11
Deleted Figure 24............................................................................ 11
Removed Fast Transient Burst Immunity
(IEC1000-4-4) S
Updated Outline Dimensions....................................................... 13
Changes to Ordering Guide.......................................................... 13
10/04—Rev. A to Rev. B
Updated Format..................................................................Universal
Changes to Power-Supply Current, Table 1 .................................. 3
Updated Outline Dimensions....................................................... 14
Changes to Ordering Guide.......................................................... 14
5/00—Rev. 0 to Rev. A
ection ................................................................... 12
Test Circuits and Switching Characteristics...................................7
Typical Perf or m an c e Charac t e r istics ..............................................9
Standards and Testing .................................................................... 11
ESD Testing ................................................................................. 11
Applications Information.............................................................. 12
Differential Data Transmission ................................................ 12
Cable and Data Rate................................................................... 12
Receiver Open-Circuit Fail-Safe............................................... 12
Outline Dimensions ....................................................................... 13
Ordering Guide .......................................................................... 13
Rev. C | Page 2 of 16
ADM3485E
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SPECIFICATIONS
VCC = +3.3 V ± 0.3 V. All specifications T
Table 1.
Parameter Symbol Min Typ Max Unit Test Conditions/Comments
DRIVER
Differential Outputs
Differential Output Voltage V
1.5 V RL = 54 Ω (RS-485) (see Figure 3)
1.5 V RL = 60 Ω (RS-485) (see Figure 4)
∆|VOD| for Complementary Output States1∆V
Common-Mode Output Voltage V
∆|VOC| for Complementary Output States1∆V
Short-Circuit Output Current I
250 mA V
Logic Inputs
Input High Voltage V
Input Low Voltage V
Logic Input Current I
RECEIVER
Differential Inputs
Differential Input Threshold Voltage V
Input Voltage Hysteresis ∆V
Input Resistance (A, B) R
Input Current (A, B) I
–0.8 mA DE = 0 V, VCC = 0 V or 3.6 V, VIN = –7 V
RO Logic Output
Output Voltage High V
Output Voltage Low V
Short-Circuit Output Current I
Tristate Output Leakage Current I
POWER SUPPLY CURRENT
Voltage Range V
Supply Current I
Shutdown Current I
ESD PROTECTION
A, B Pins ±15 kV Human body model
All Pins Except A, B ±4 kV Human body model
1
Δ|VOD| and Δ|VOC| are the changes in VOD and VOC, respectively, when DI input changes state.
MIN
to T
, unless otherwise noted.
MAX
OD
OD
OC
OC
OSD
IH
IL
IN1
TH
TH
IN
IN2
OH
OL
OSR
OZR
CC
CC
2.0 V RL = 100 Ω (RS-422) (see Figure 3)
0.2 V RL = 54 Ω or 100 Ω (see Figure 3)
3 V RL = 54 Ω or 100 Ω ( see Figure 3)
0.2 V RL = 54 Ω or 100 Ω (see Figure 3)
–250 mA V
0.8 V
2.0 V
±2 μA
–0.2 +0.2 V –7 V < VCM < +12 V
50 mV VCM = 0 V
12 kΩ –7 V < VCM < +12 V
1.0 mA DE = 0 V, VCC = 0 V or 3.6 V, VIN = 12 V
VCC – 0.4 V V I
0.4 V I
±8 ±60 mA 0 V < VRO < V
±1 μA VCC = 3.6 V, 0 V < V
3.0 3.6 V
1.1 2.2 mA
0.95 1.9 mA
SHDN
0.002 1 μA
= –7 V
OUT
= 12 V
OUT
DE, DI, RE
DE, DI, RE
DE, DI, RE
= –1.5 mA, VID = 200 mV (see Figure 5)
OUT
= 2.5 mA, VID = 200 mV (see Figure 5)
OUT
CC
< V
OUT
CC
No load, DI = 0 V or V
= 0 V or V
RE
CC
No load, DI = 0 V or V
= 0 V
RE
DE = 0 V, RE
= VCC, DI = 0 V or V
, DE = VCC,
CC
, DE = 0 V,
CC
CC
Rev. C | Page 3 of 16
ADM3485E
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TIMING SPECIFICATIONS
VCC = 3.3 V, TA = 25°C.
Table 2.
Parameter Symbol Min Typ Max Unit Test Conditions/Comments
DRIVER
Maximum Data Rate 12 15
Differential Output Delay t
Differential Output Transition Time t
DD
TD
Propagation Delay
From Low to High Level t
From High to Low Level t
|t
− t
PLH
| Propagation Delay Skew t
PHL
PLH
PHL
PDS
Enable/Disable Timing
Enable Time to Low Level t
Enable Time to High Level t
Disable Time from Low Level t
Disable Time from High Level t
Enable Time from Shutdown to Low Level t
Enable Time from Shutdown to High Level t
PZL
PZH
PLZ
PHZ
PSL
PSH
RECEIVER
Propagation Delay
From Low to High Level t
From High to Low Level t
|t
− t
RPLH
| Propagation Delay Skew t
RPHL
RPLH
RPHL
RPDS
Enable/Disable Timing
Enable Time to Low Level t
Enable Time to High Level t
Disable Time from Low Level t
Disable Time from High Level t
Enable Time from Shutdown to Low Level t
Enable Time from Shutdown to High Level t
Time to Shutdown
1
The transceivers are put into shutdown mode by bringing the RE high and the DE low. If the inputs are in this state for less than 80 ns, the parts are guaranteed not to
enter shutdown. If the parts are in this state for 300 ns or more, the parts are guaranteed to enter shutdown.
1
t
RPZL
RPZH
RPLZ
RPHZ
RPSL
RPSH
SHDN
1 22 35 ns RL = 60 Ω, CL1 = CL2 = 15 pF (see Figure 6)
3 11 25 ns RL = 60 Ω, CL1 = CL2 = 15 pF (see Figure 6)
7 23 35 ns RL = 27 Ω (see Figure 7)
7 23 35 ns RL = 27 Ω (see Figure 7)
–1.4 ±8 ns RL = 27 Ω (see Figure 7)
42 90 ns RL = 110 Ω (see Figure 9)
42 90 ns RL = 110 Ω (see Figure 8)
35 80 ns RL = 110 Ω (see Figure 9)
35 80 ns RL = 110 Ω (see Figure 8)
650 900 ns RL = 110 Ω (see Figure 9)
650 900 ns RL = 110 Ω (see Figure 8)
25 62 90 ns VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10)
25 62 90 ns VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10)
6 ±10 ns VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10)
25 50 ns CL = 15 pF (see Figure 11)
25 50 ns CL = 15 pF (see Figure 11)
25 45 ns CL = 15 pF (see Figure 11)
25 45 ns CL = 15 pF (see Figure 11)
720 1400 ns CL = 15 pF (see Figure 11)
720 1400 ns CL = 15 pF (see Figure 11)
80 190 300 ns
Rev. C | Page 4 of 16
ADM3485E
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ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 3.
Parameter Values
VCC to GND –0.3 V to +6 V
Digital Input/Output Voltage (DE, RE, DI)
Receiver Output Voltage (RO) –0.3 V to (VCC + 0.3 V)
Driver Output (A, B)/
Receiver Input (A, B) Voltage −8 V to +13 V
Driver Output Current ±250 mA
Power Dissipation (8-Lead SOIC_N) 650 mW
Operating Temperature Range –40°C to +85°C
Storage Temperature Range –65°C to +150°C
Lead Temperature, Soldering (10 sec) 300°C
Vapor Phase (60 sec) 215°C
Infrared (15 sec) 220°C
ESD Rating
Human Body Model (A, B) ±15 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.
–0.3 V to +6 V
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 θ
8-Lead SOIC_N 158 °C/W
JA
Unit
ESD CAUTION
Rev. C | Page 5 of 16
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