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Full-Duplex, Low Power, Slew Rate Limited, EIA RS-485 Transceivers
ADM488A/ADM489A
FEATURES
Complies with ANSI TIA/EIA-485-A-1998 and ISO 8482: 1987(E) 250 kbps data rate Single 5 V 10% supply -7 V to +12 V bus common-mode range Connect up to 32 nodes on the bus Reduced slew rate for low EM interference Short-circuit protection 30 A supply current
FUNCTIONAL BLOCK DIAGRAMS
ADM488A
A RO
R
B
Z DI
D
08498-001
Y
Figure 1. ADM488A
APPLICATIONS
Low power RS-485 and RS-422 systems DTE-DCE interface Packet switching Local area networks Data concentration Data multiplexers Integrated services digital network (ISDN)
RO RE DE
ADM489A
A R B
Z Y
08498-002
DI
D
GENERAL DESCRIPTION
The ADM488A and ADM489A are low power, differential line transceivers suitable for communication on multipoint bus transmission lines. They are intended for balanced data transmission and comply with both RS-485 and RS-422 standards of the Electronics Industries Association (EIA). Both products contain a single differential line driver and a single differential line receiver, making them suitable for full-duplex data transfer. The ADM489A contains an additional receiver and driver enable control. The input impedance is 12 k, allowing 32 transceivers to be connected on the bus. The ADM488A/ADM489A operate from a single 5 V 10% power supply.
Figure 2. ADM489A
Excessive power dissipation that is caused by bus contention or output shorting is prevented by a thermal shutdown circuit. 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 ADM488A/ADM489A are fabricated on BiCMOS, an advanced mixed technology process combining low power CMOS with fast switching bipolar technology. The ADM488A/ADM489A are fully specified over the industrial temperature range and are available in SOIC and MSOP packages.
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)2009 Analog Devices, Inc. All rights reserved.
ADM488A/ADM489A TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagrams ............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Specifications .................................................................. 4 Absolute Maximum Ratings............................................................ 5 ESD Caution .................................................................................. 5 Pin Configurations and Function Descriptions ........................... 6 Typical Performance Characteristics ..............................................8 Test Circuits ........................................................................................9 Switching Characteristics .......................................................... 10 Theory of Operation .......................................................................11 Applications Information .............................................................. 13 Differential Data Transmission ................................................ 13 Cable and Data Rate ................................................................... 13 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 15
REVISION HISTORY
10/09--Revision 0: Initial Version
Rev. 0 | Page 2 of 16
ADM488A/ADM489A SPECIFICATIONS
VCC = 5 V 10%; all specifications TMIN to TMAX, unless otherwise noted. Table 1.
Parameter DRIVER Differential Output Voltage Symbol VOD 2.0 1.5 1.5 |VOD| for Complementary Output States Common-Mode Output Voltage |VOC| for Complementary Output States Output Short-Circuit Current VOUT CMOS Input Logic Threshold Low CMOS Input Logic Threshold High Logic Input Current (DE, DI) RECEIVER Differential Input Threshold Voltage Input Voltage Hysteresis Input Resistance Input Current (A, B) Logic Enable Input Current (RE) CMOS Output Voltage Low CMOS Output Voltage High Short-Circuit Output Current Three-State Output Leakage Current POWER SUPPLY CURRENT VOL VOH 4.0 7 VOC Min Typ Max 5.0 5.0 5.0 5.0 0.2 3.0 0.2 250 0.8 1.0 VTH VTH -0.2 70 12 1 -0.8 1 0.4 85 1.0 30 37 60 74 +0.2 Unit V V V V V V V mA V V A V mV k mA mA A V V mA A A A Test Conditions/Comments R = , see Figure 11 VCC = 5 V, R = 50 (RS-422), see Figure 11 R = 27 (RS-485), see Figure 11 VTST = -7 V to +12 V, see Figure 12, VCC = 5 V 5% R = 27 or 50 , see Figure 11 R = 27 or 50 , see Figure 11 R = 27 or 50 -7 V VO +12 V
VINL VINH
2.0
1.4 1.4
-7 V VCM +12 V VCM = 0 V -7 V VCM +12 V VIN = 12 V VIN = -7 V IOUT = +4.0 mA IOUT = -4.0 mA VOUT = GND or VCC 0.4 V VOUT 2.4 V Outputs unloaded, receivers enabled DE = 0 V (disabled) DE = 5 V (enabled)
ICC
Rev. 0 | Page 3 of 16
ADM488A/ADM489A
TIMING SPECIFICATIONS
VCC = 5 V 10%. All specifications TMIN to TMAX, unless otherwise noted. Table 2.
Parameter DRIVER Propagation Delay Input to Output Driver Output Skew Driver Rise/Fall Time Driver Enable to Output Valid Driver Disable Timing Maximum Data Rate RECEIVER Propagation Delay Input to Output Skew Receiver Enable Receiver Disable Maximum Data Rate Symbol tPLH, tPHL tSKEW tDR, tDF tZL, tZH tLZ, tHZ 250 250 300 250 250 100 10 10 250 Min 250 100 Typ Max 2000 800 2000 2000 3000 Unit ns ns ns ns ns kbps ns ns ns ns kbps Test Conditions/Comments RL differential = 54 , CL1 = CL2 = 100 pF, see Figure 15 RL differential = 54 , CL1 = CL2 = 100 pF, see Figure 15 RL differential = 54 , CL1 = CL2 = 100 pF, see Figure 15 RL = 500 , CL = 100 pF, see Figure 12 RL = 500 , CL = 15 pF, see Figure 12
tPLH, tPHL |tPLH - tPHL| tEN1 tEN2
2000 50 50
CL = 15 pF, see Figure 15 RL = 1 k, CL = 15 pF, see Figure 14 RL = 1 k, CL = 15 pF, see Figure 14
Rev. 0 | Page 4 of 16
ADM488A/ADM489A ABSOLUTE MAXIMUM RATINGS
TA = 25C, unless otherwise noted. Table 3.
Parameter VCC Inputs Driver Input (DI) Control Inputs (DE, RE) Receiver Inputs (A, B) Outputs Driver Outputs Receiver Output Power Dissipation 8-Lead SOIC JA, Thermal Impedance Power Dissipation 14-Lead SOIC JA, Thermal Impedance Operating Temperature Range Industrial (A Version) Storage Temperature Range Lead Temperature (Soldering, 10 sec) Vapor Phase (60 sec) Infrared (15 sec) Rating 7V -0.3 V to VCC + 0.3 V -0.3 V to VCC + 0.3 V -14 V to +14 V -14 V to +12.5 V -0.5 V to VCC + 0.5 V 520 mW 110C/W 800 mW 120C/W -40C to +85C -65C to +150C 300C 215C 220C
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.
ESD CAUTION
Rev. 0 | Page 5 of 16
ADM488A/ADM489A PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
VCC 1 RO 2
8
A
Figure 3. ADM488A Pin Configuration
Table 4. ADM488A Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 Mnemonic VCC RO DI GND Y Z B A Description Power Supply, 5 V 10%. Receiver Output. When A > B by 200 mV, RO = high. If A < B by 200 mV, RO = low. Driver Input. A logic low on DI forces Y low and Z high, whereas a logic high on DI forces Y high and Z low. Ground Connection, 0 V. Noninverting Driver, Differential Output Y. Inverting Driver, Differential Output Z. Inverting Receiver, Input B. Noninverting Receiver, Input A.
Rev. 0 | Page 6 of 16
08498-003
B TOP VIEW DI 3 (Not to Scale) 6 Z GND 4 5Y
7
ADM488A
ADM488A/ADM489A
NC RO RE DE DI GND GND
1 2 3 4 5 6 7 14 13
VCC NC A B Z Y
08498-004
RO RE DE DI
1 2 3 4
10
VCC A B
08498-005
ADM489A
TOP VIEW (Not to Scale)
12 11 10 9 8
ADM489A
TOP VIEW (Not to Scale)
9 8 7 6
Z Y
GND 5
NC
NC = NO CONNECT
Figure 4. ADM489A SOIC_N Pin Configuration
Figure 5. ADM489A MSOP Pin Configuration
Table 5. ADM489A Pin Function Descriptions
Pin No. SOIC_N 1, 8, 13 2 3 4 5 6, 7 9 10 11 12 14
1
MSOP N/A 1 1 2 3 4 5 6 7 8 9 10
Mnemonic NC RO RE DE DI GND Y Z B A VCC
Description No Connect. No connections are required to this pin. Receiver Output. When enabled, if A > B by 200 mV, RO = high. If A < B by 200 mV, RO = low. Receiver Output Enable. A low level enables the receiver output, RO. A high level places the ADM489A in a high impedance state. Driver Output Enable. A high level enables the driver differential outputs (Y and Z). A low level places the ADM489A in a high impedance state. Driver Input. When the driver is enabled, a logic low on DI forces Y low and Z high, whereas a logic high on DI forces Y high and Z low. Ground Connection, 0 V. Noninverting Driver, Differential Output Y. Inverting Driver, Differential Output Z. Inverting Receiver, Input B. Noninverting Receiver, Input A. Power Supply, 5 V 10%.
N/A means not applicable.
Rev. 0 | Page 7 of 16
ADM488A/ADM489A TYPICAL PERFORMANCE CHARACTERISTICS
45 40 35
OUTPUT CURRENT (mA)
0 -10 -20
OUTPUT CURRENT (mA)
08498-015
30 25 20 15 10 5 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 OUTPUT VOLTAGE (V)
-30 -40 -50 -60 -70 -80
08498-018 08498-019
-90 2.5
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
OUTPUT VOLTAGE (V)
Figure 6. Output Current vs. Receiver Output Low Voltage
0 -2 -4
OUTPUT CURRENT (mA)
Figure 9. Output Current vs. Driver Output High Voltage
0 -10 -20 -30 -40 -50 -60 -70 -80 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT VOLTAGE (V)
-6 -8 -10 -12 -14 -16 -18
08498-016
-20 3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
5.0
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
Figure 7. Output Current vs. Receiver Output High Voltage
90 80 70
OUTPUT CURRENT (mA)
Figure 10. Output Current vs. Driver Differential Output Voltage
60 50 40 30 20 10
08498-017
0 0 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT VOLTAGE (V)
Figure 8. Output Current vs. Driver Output Low Voltage
Rev. 0 | Page 8 of 16
ADM488A/ADM489A TEST CIRCUITS
+1.5V VCC S1 -1.5V
08498-006
R VOD
R VOC
RL S2 RE
08498-009
CL VOUT
RE IN
Figure 11. Driver Voltage Measurement Test Circuit
Figure 14. Receiver Enable/Disable Test Circuit
3V DE
375
Y DI D Z
08498-007
CL1 RLDIFF CL2
A RO R B RE
08498-010
VOD3
60 375
VTST
Figure 12. Driver Enable/Disable Test Circuit
Figure 15. Driver/Receiver Propagation Delay Test Circuit
VCC A 0V OR 3V DE B S1 CL VOUT
RL S2
08498-008
DE IN
Figure 13. Driver Voltage Measurement Test Circuit
Rev. 0 | Page 9 of 16
ADM488A/ADM489A
SWITCHING CHARACTERISTICS
VCC VCC/2 0V VCC/2
VCC
tPLH
Z 1/2VO VO Y
tPHL
DE
0.5VCC
0.5VCC
0V
tZL
2.3V
tLZ
Y, Z
VOL + 0.5V VOL
+VO VDIFF -VO
90% POINT
VDIFF = V(Y) - V(Z)
90% POINT
Y, Z
tZH
2.3V
tHZ
VOH
08498-013
VOH - 0.5V 0V
10% POINT
10% POINT
tDR
tDF
Figure 16. Driver Propagation Delay, Rise/Fall Timing
08498-011
Figure 18. Driver Enable/Disable Timing
0.7VCC RE 0.5VCC 0.5VCC 0.3VCC
A-B
0V
0V
tZL
1.5V OUTPUT LOW
tLZ
tPLH
tPHL
VOH
RO
VOL + 0.5V VOL
tZH
OUTPUT HIGH RO 0V
tHZ
VOH
08498-014
RO
1.5V
tSKEW = |tPLH - tPHL|
1.5V VOL
08498-012
1.5V
VOH - 0.5V
Figure 17. Receiver Propagation Delay
Figure 19. Receiver Enable/Disable Timing
Rev. 0 | Page 10 of 16
ADM488A/ADM489A THEORY OF OPERATION
The ADM488A/ADM489A are ruggedized RS-485 transceivers that operate from a single 5 V supply. They contain protection against radiated and conducted interference and are ideally suited for operation in electrically harsh environments or where cables can be plugged/unplugged. They are also immune to high RF field strengths without special shielding precautions. The ADM488A/ADM489A are intended for balanced data transmission and comply with both EIA RS-485 and RS-422 standards. They contain a differential line driver and a differential line receiver, and are suitable for full-duplex data transmission. The input impedance on the ADM488A/ADM489A is 12 k, allowing up to 32 transceivers on the differential bus. The ADM488A/ADM489A operate from a single 5 V 10% power supply. 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 ADM488A/ADM489A can transmit at data rates up to 250 kbps. Figure 20 shows a typical application for the ADM488A/ADM489A, a full-duplex link where data transfers at rates of up to 250 kbps. A terminating resistor is shown at both ends of the link. This termination is not critical because
VCC VCC
the slew rate is controlled by the ADM488A/ADM489A and reflections are minimized. The communications network can be extended to include multipoint connections, as shown in Figure 22. As many as 32 transceivers can be connected to the bus. Table 6 and Table 7 show the truth tables for transmitting and receiving. Table 6. Transmitting Truth Table
Inputs RE X X1 0 1
1
Outputs DI 1 0 X1 X1 Z 0 1 High-Z Hgh-Z Y 1 0 High-Z High-Z
1
DE 1 1 0 0
X is don't care.
Table 7. Receiving Truth Table
Inputs RE 0 0 0 1
1
Output RO 1 0 1 High-Z
DE 0 0 0 0
A to B +0.2 V -0.2 V Inputs open circuit X1
X is don't care.
VCC
ADM488A
RO R
A B Z RT VCC
ADM488A
Y D Z B RT A R RO DI
DI
D
Y
NOTES 1. MAXIMUM NUMBER OF NODES = 32.
Figure 20. ADM488A/ADM489A Full-Duplex Data Link
Rev. 0 | Page 11 of 16
08498-021
GND
GND
ADM488A/ADM489A
MAXIMUM NUMBER OF NODES = 32 MASTER A RO RE DE DI D Z Y R B
VCC
SLAVE Y
RT
VCC
D Z
DI DE
B
RE R RO
RT
A
ADM488A
A SLAVE B Z Y A B Z Y SLAVE
ADM488A
ADM488A
R D
R D
ADM488A
RO
RE
DE
DI
RO
RE
DE
DI
08498-023
NOTES 1. RT IS EQUAL TO THE CHARACTERISTIC IMPEDANCE OF THE CABLE.
Figure 21. Typical RS-485 Full-Duplex Application
Rev. 0 | Page 12 of 16
ADM488A/ADM489A APPLICATIONS INFORMATION
DIFFERENTIAL DATA TRANSMISSION
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, which appear as common-mode voltages on the line. Two main standards that specify the electrical characteristics of transceivers used in differential data transmission are approved by the EIA. The RS-422 standard specifies data rates up to 10 Mbps and line lengths up to 4000 ft. A single driver can drive a transmission line with up to 10 receivers. To cater to true multipoint communications, the RS-485 standard was defined to meet or exceed the requirements of RS-422. It also allows up to 32 drivers and 32 receivers to be connected 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 RS-485 is that the RS-485 drivers can be disabled, thereby allowing up to 32 receivers to be 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. Table 8. Comparison of RS-422 and RS-485 Interface Standards
Specification Transmission Type Maximum Data Rate Maximum Cable Length Minimum Driver Output Voltage Driver Load Impedance Receiver Input Resistance Receiver Input Sensitivity Receiver Input Voltage Range Number of Drivers/Receivers per Line
RT
CABLE AND DATA RATE
The transmission line of choice for RS-485 communications is a twisted pair. 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. The ADM488A/ADM489A are designed for bidirectional data communications on multipoint transmission lines. A typical application with a multipoint transmission network is illustrated in Figure 22. An RS-485 transmission line can have up to 32 transceivers on the bus. Only one driver can transmit at a particular time, but multiple receivers can be simultaneously enabled. 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.
RS-422 Differential 10 Mbps 4000 ft. 2 V 100 4 k minimum 200 mV -7 V to +7 V 1/10
RT
RS-485 Differential 10 Mbps 4000 ft. 1.5 V 54 12 k minimum 200 mV -7 V to +12 V 32/32
D
D
R
R
R D D
R
08498-022
Figure 22. Typical RS-485 Network
Rev. 0 | Page 13 of 16
ADM488A/ADM489A OUTLINE DIMENSIONS
3.10 3.00 2.90
10
6
3.10 3.00 2.90 PIN 1 IDENTIFIER
1
5.15 4.90 4.65
5
0.50 BSC 0.95 0.85 0.75 0.15 0.05 COPLANARITY 0.10 0.30 0.15 15 MAX 1.10 MAX 0.70 0.55 0.40
091709-A
6 0
0.23 0.13
COMPLIANT TO JEDEC STANDARDS MO-187-BA
Figure 23. 10-Lead Mini Small Outline Package [MSOP] (RM-10) Dimensions shown in millimeters
5.00 (0.1968) 4.80 (0.1890)
8
5 4
4.00 (0.1574) 3.80 (0.1497)
1
6.20 (0.2441) 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) 0.25 (0.0099) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
0.51 (0.0201) 0.31 (0.0122)
COMPLIANT TO JEDEC STANDARDS MS-012-A A 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 24. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
Rev. 0 | Page 14 of 16
012407-A
ADM488A/ADM489A
8.75 (0.3445) 8.55 (0.3366)
14 1 8 7
4.00 (0.1575) 3.80 (0.1496)
6.20 (0.2441) 5.80 (0.2283)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122)
1.75 (0.0689) 1.35 (0.0531) SEATING PLANE
0.50 (0.0197) 0.25 (0.0098) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
COMPLIANT TO JEDEC STANDARDS MS-012-AB 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 25. 14-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-14) Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model ADM488ABRMZ 1 ADM488ABRMZ-REEL71 ADM488ABRZ1 ADM488ABRZ-REEL71 ADM489ABRMZ1 ADM489ABRMZ-REEL71 ADM489ABRZ1 ADM489ABRZ-REEL71 Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description 10-Lead Mini Small Outline Package [MSOP] 10-Lead Mini Small Outline Package [MSOP] 8-Lead Standard Small Outline Package, Narrow Body [SOIC_N] 8-Lead Standard Small Outline Package, Narrow Body [SOIC_N] 10-Lead Mini Small Outline Package [MSOP] 10-Lead Mini Small Outline Package [MSOP] 14-Lead Standard Small Outline Package, Narrow Body [SOIC_N] 14-Lead Standard Small Outline Package, Narrow Body [SOIC_N] Package Option RM-10 RM-10 R-8 R-8 RM-10 RM-10 R-14 R-14 F0G F0G Branding F0F F0F
1
Z = RoHS Compliant Part.
Rev. 0 | Page 15 of 16
060606-A
ADM488A/ADM489A NOTES
(c)2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08498-0-10/09(0)
Rev. 0 | Page 16 of 16

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