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3.3 V Slew Rate Limited, Half Duplex RS-485/RS-422 Transceiver ADM3493
FEATURES
Operates with 3.3 V supply Interoperable with 5 V logic EIA RS-422 and RS-485 compliant over full CM range Data rate: 250 kbps Half duplex transceiver Reduced slew rates for low EMI 2 nA supply current in shutdown mode Up to 256 transceivers on a bus -7 V to +12 V bus common-mode range Specified over -40C to +85C temperature range 8 ns skew Available in 8-lead SOIC
FUNCTIONAL BLOCK DIAGRAM
VCC
ADM3493
RO RE DE DI D
05715-001
R A B
GND
Figure 1.
APPLICATIONS
Low power RS-485 applications EMI sensitive systems DTE-DCE interfaces Industrial control Packet switching Local area networks Level translators
GENERAL DESCRIPTION
The ADM3493 is a low power, differential line transceiver designed to operate using a single 3.3 V power supply. Low power consumption, coupled with a shutdown mode, makes it ideal for power-sensitive applications. The ADM3493 is suitable for communication on multipoint bus transmission lines. The device contains one driver and one receiver. Designed for half-duplex communication, the ADM3493 features a slew rate limited driver that minimizes EMI and reduces reflections caused by improperly terminated cables, allowing error-free data transmission at data rates up to 250 kbps.
The receiver input impedance is 96 k, allowing up to 256 transceivers to be connected on the bus. A thermal shutdown circuit prevents excessive power dissipation caused by bus contention or by output shorting. If a significant temperature increase is detected in the internal driver circuitry during fault conditions then the thermal shutdown circuit forces the driver output into a high impedance state. The receiver contains a failsafe feature that results in a logic high output state, if the inputs are unconnected (floating). The ADM3493 is fully specified over the commercial and industrial temperature ranges and is available in an 8-lead SOIC.
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)2005 Analog Devices, Inc. All rights reserved.
ADM3493 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 ESD Caution.................................................................................. 5 Pin Configurations and Function Descriptions ........................... 6 Test Circuits....................................................................................... 7 Switching Characteristics .................................................................8 Typical Performance Characteristics ..............................................9 Circuit Description......................................................................... 11 Reduced EMI and Reflections .................................................. 11 Low Power Shutdown Mode..................................................... 11 Driver Output Protection.......................................................... 11 Propagation Delay ...................................................................... 11 Typical Applications................................................................... 11 Outline Dimensions ....................................................................... 12 Ordering Guide .......................................................................... 12
REVISION HISTORY
10/05--Rev. 0: Initial Version
Rev. 0 | Page 2 of 12
ADM3493 SPECIFICATIONS
VCC = 3.3 V 0.3 V, TA = TMIN to TMAX, unless otherwise noted. Table 1.
Parameter DRIVER Differential Output Voltage, VOD Min 2.0 1.5 1.5 |VOD| for Complementary Output States 1 Common-Mode Output Voltage, VOC |VOC| for Common-Mode Output Voltage1 DRIVER INPUT LOGIC CMOS Input Logic Threshold Low, VIH CMOS Input Logic Threshold High, VIL CMOS Logic Input Current, IN1 Input Current (A, B), IN2 0.2 3 0.2 0.8 2.0 2 60 -60 RECEIVER Differential Input Threshold Voltage, VTH Input Hysteresis, VTH CMOS Output Voltage High, VOH CMOS Output Voltage Low, VOL Three-State Output Leakage Current, IOZR Input Resistance, RIN POWER SUPPLY CURRENT Supply Current -0.2 50 Vcc - 0.4 0.4 1 96 1.1 0.95 Supply Current in Shutdown Mode, ISHDN Driver Short-Circuit Output Current, IOSD Receiver Short-Circuit Output Current, IOSR
1
Typ
Max
Units V V V V V V V V A A A
Test Conditions/Comments RL = 100 (RS-422), Vcc = 3.3 V 5% (see Figure 3) RL = 54 (RS-485) (see Figure 3) RL = 60 (RS-485), Vcc = 3.3 V (see Figure 4) RL = 54 or 100 (see Figure 3) RL = 54 or 100 (see Figure 3) RL = 54 or 100 (see Figure 3) DE, DI, RE DE, DI, RE DE, DI, RE VIN = 12 V VIN = -7 V DE = 0 V VCC = 0 V or 3.6 V
0.2
V mV V V A k mA mA A mA mA mA
-7V < VCM < + 12 V VCM = 0 V IOUT = -1.5 mA, VID = 200 mV (see Figure 5) IOUT = 2.5mA, VID = 200mV (see Figure 5) Vcc = 3.6 V, 0 V VOUT Vcc -7 V < VCM < + 12 V DE = VCC RE = 0 V or VCC DE = VCC RE = 0 V No load, DI = 0 V or VCC
2.2 1.9 1 -250 250 60
0.002
8
DE = 0 V, RE = VCC, DI = VCC or 0 V VOUT = -7 V VOUT = 12 V 0 V < VRO < VCC
VOD and VOC are the changes in VOD and VOC, respectively, when DI input changes state.
Rev. 0 | Page 3 of 12
ADM3493
TIMING SPECIFICATIONS
VCC = 3.3 V, TA = 25C, unless otherwise noted. Table 2.
Parameter DRIVER Differential Output Delay, tDD Differential Output Transition Time, tTD Propagation Delay, Low-to-High Level, tPLH Propagation Delay, High-to-Low Level, tPHL |tPLH - tPHL| Propagation Delay Skew1, tPDS DRIVER OUTPUT ENABLE/DISABLE TIMES Output Enable Time to Low Level, tPZL Output Enable Time to High Level, tPZH Output Disable Time from High Level, tPHZ Output Disable Time from Low Level, tPLZ Output Enable Time from Shutdown to Low Level, tPSL Output Enable Time from Shutdown to High Level, tPSH RECEIVER Time to Shutdown2, tSHDN Propagation Delay, Low-to-High Level, tRPLH Propagation Delay, High-to-Low Level, tRPHL |tPLH - tPHL| Propagation Delay Skew, tRPDS RECEIVER OUTPUT ENABLE/DISABLE TIMES Output Enable Time to Low Level, tPRZL Output Enable Time to High Level, tPRZH Output Disable Time from High Level, tPRHZ Output Disable Time from Low Level, tPRLZ Output Enable Time from Shutdown to Low Level, tPRSL Output Enable Time from Shutdown to High Level, tPRSH
1 2
Min 600 400 700 700
Typ 900 700 1000 1000 100 900 600 50 50 1.9 2.2
Max 1400 1200 1500 1500
Units ns ns ns ns ns ns ns ns ns s s
Test Conditions/Comments RL = 60 (see Figure 6 and Figure 12) RL = 60 (see Figure 6 and Figure 12) RL = 27 (see Figure 7 and Figure 13) RL = 27 (see Figure 7 and Figure 13) RL = 27 (see Figure 7 and Figure 13) RL = 110 (see Figure 9 and Figure 15) RL = 110 (see Figure 8 and Figure 14) RL = 110 (see Figure 8 and Figure 14) RL = 110 (see Figure 9 and Figure 15) RL = 110 (see Figure 9 and Figure 15) RL = 110 (see Figure 8 and Figure 14)
1300 800 80 80 2.7 3.0
80 25 25
190 75 75
300 180 180 50
ns ns ns ns
VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10 and Figure 16) VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10 and Figure 16) VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10 and Figure 16) CL = 15 pF (see Figure 11 and Figure 17) CL = 15 pF (see Figure 11 and Figure 17) CL = 15 pF (see Figure 11 and Figure 17) CL = 15 pF (see Figure 11 and Figure 17) CL = 15 pF (see Figure 11 and Figure 17) CL = 15 pF (see Figure 11 and Figure 17)
25 25 25 25 720 720
50 50 45 45 1400 1400
ns ns ns ns ns ns
Measured on |tPLH (A) - tPHL (A)| and |tPLH (B) - tPHL (B)|. The transceivers are put into shutdown by bringing RE high and DE low. If the inputs are in this state for less than 80 ns, the parts are guaranteed not to enter shutdown. If the inputs are in this state for at least 300 ns, the parts are guaranteed to enter shutdown.
Rev. 0 | Page 4 of 12
ADM3493 ABSOLUTE MAXIMUM RATINGS
TA = 25C, unless otherwise noted. Table 3.
Parameter VCC to GND Digital I/O Voltage (DE, RE, DI) Digital I/O Voltage (ROUT) Driver Output/Receiver Input Voltage Operating Temperature Range Storage Temperature Range JA Thermal Impedance 8-Lead SOIC Lead Temperature Soldering (10 seconds) Vapor Phase (60 seconds) Infrared (15 seconds) Rating 7V -0.3 V to VCC + 0.3 V VCC - 0.5 V to VCC + 0.5 V -7.5 V to +12.5 V -40C to +85C -65C to +125C 121C/W 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
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. 0 | Page 5 of 12
ADM3493 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
RO 1 RE 2 DE 3 DI 4
8
ADM3493
TOP VIEW (Not to Scale)
VCC B GND
05715-002
7 6 5
A
Figure 2. Pin Configuration
Table 4. . Pin Function Descriptions
Pin No. 1 2 Mnemonic RO RE Description Receiver Output. When enabled, if A > B by 200 mV, then RO = high. If A < B by 200 mV, then RO = low. Receiver Output Enable. A low level enables the receiver output, RO. A high level places it in a high impedance state. If RE is high and DE is low, the device enters a low power shutdown mode. Driver Output Enable. A high level enables the driver differential Outputs A and B. A low level places it in a high impedance state. If RE is high and DE is low, the device enters a low power shutdown mode. Driver Input. When the driver is enabled, a logic low on DI forces A low and B high while a logic high on DI forces A high and B low. Ground. Noninverting Receiver Input A and Noninverting Driver Output A. Inverted Receiver Input B and Inverted Driver Output B. Power Supply, 3.3 V 0.3 V.
3
DE
4 5 6 7 8
DI GND A B VCC
Rev. 0 | Page 6 of 12
ADM3493 TEST CIRCUITS
A RL/2 VOD
05715-003
S1 0V OR 3V D CL = 50pF2
VOC
OUT RL = 110
RL/2 B
GENERATOR1
50 VOM = VOH + VOL 2 1.5V
05715-008
Figure 3. Driver VOD and VOC
375
1PPR = 250kHz, 50% DUTY CYCLE, t 6.0ns, Z = 50. R O 2C INCLUDES PROBE AND STRAY CAPACITANCE. L
Figure 8. Driver Enable and Disable Times (tPZH, tPSH, tPHZ)
D VCC VOD RL VCM = -7V TO +12V
VCC RL = 110 S1 0V OR 3V D CL = 50pF2 GENERATOR1 50 OUT
375
Figure 4. Driver VOD with Varying Common-Mode Voltage
VID
R
05715-005
VOL
IOL (+)
VOH
IOH (-)
1PPR = 250kHz, 50% DUTY CYCLE, t 6.0ns, Z = 50. R O 2C INCLUDES PROBE AND STRAY CAPACITANCE. L
Figure 5. Receiver VOH and VOL
CL D GENERATOR1 50 VCC CL = 15pF2
05715-006
Figure 9. Driver Enable and Disable Times (tPZL, tPSL, tPLZ)
OUT CL = 15pF2
VID
RL = OUT 60
GENERATOR1
R
50
1.5V 0 VOM =
VCC 2
05715-010
1PPR = 250kHz, 50% DUTY CYCLE, t 6.0ns, Z = 50. R O 2C INCLUDES PROBE AND STRAY CAPACITANCE. L
Figure 6. Driver Differential Output Delay and Transition Times
VOM RL = 27 S1 D GENERATOR1 50 VCC VOH + VOL 2 OUT CL = 15pF2
1PPR = 250kHz, 50% DUTY CYCLE, t 6.0ns, Z = 50. R O 2C INCLUDES PROBE AND STRAY CAPACITANCE. L
Figure 10. Receiver Propagation Delay
+1.5V -1.5V S3 VID R CL2 GENERATOR1 1k S2 S1 VCC
50
VOM =
1.5V
05715-007
05715-009
0
05715-004
1PPR = 250kHz, 50% DUTY CYCLE, t 6.0ns, Z = 50. R O 2C INCLUDES PROBE AND STRAY CAPACITANCE. L
1PPR = 250kHz, 50% DUTY CYCLE, t 6.0ns, Z = 50. R O 2C INCLUDES PROBE AND STRAY CAPACITANCE. L
Figure 7. Driver Propagation Delays
Figure 11. Receiver Enable and Disable Times
Rev. 0 | Page 7 of 12
05715-011
ADM3493 SWITCHING CHARACTERISTICS
+3V IN 1.5V 1.5V 0
3V IN 1.5V 1.5V 0
tDD
50% 10% 90% 90%
tDD
+2V
05715-012
tPSL
OUT VOM
tPLZ
VCC 0.25V VOL
05715-015
05715-016
+3V IN +1.5V
OUT
50% 10%
tTD
tTD
-2V
Figure 12. Driver Differential Output Delay and Transition Times
3V IN 1.5V 1.5V 0V
Figure 15. Driver Enable and Disable Times (tPZL, tPSL, tPLZ)
3V IN 1.5V 1.5V 0
tPLH
A OUT VOM
tPHL
VOH VOM VOL
tRPLH
VOM
tRPHL
VCC VOM 0
OUT
tPHL
B OUT VOM
tPLH
VOH
05715-013
Figure 16. Receiver Propagation Delay
+3V IN +1.5V S1 OPEN S2 CLOSED S3 = +1.5V S1 CLOSED S2 OPEN S3 = -1.5V
VOM VOL
Figure 13. Driver Propagation Delays
3V IN 1.5V 1.5V 0
tPRZH tPRSH
OUT +1.5V
0 VOH
tPRZL tPRSL
OUT +1.5V
0
VCC VOL
0
+3V IN +1.5V 0
S1 OPEN S2 CLOSED S3 = +1.5V
+3V IN +1.5V 0
S1 CLOSED S2 OPEN S3 = -1.5V
tPZH
OUT VOM
tPHZ
0.25V VOH
05715-014
OUT +0.25V
tPRHZ
VOH OUT 0 +0.25V
tPRLZ
VCC VOL
05715-017
0
Figure 14. Driver Enable and Disable Times (tPZH, tPSH, tPHZ)
Figure 17. Receiver Enable and Disable Times
Rev. 0 | Page 8 of 12
ADM3493 TYPICAL PERFORMANCE CHARACTERISTICS
30 0.8 0.7 0.6 20 25
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
05715-018
0.5 0.4 0.3 0.2
15
10
5
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 -40 -30 -20 -10
0
10
20
30
40
50
60
70
80
OUTPUT VOLTAGE (V)
TEMPERATURE (C)
Figure 18. Output Current vs. Receiver Output Low Voltage
-16 -14 -12 -10 -8 -6 -4
05715-019
Figure 21. Receiver Output Low Voltage vs. Temperature, IO = 2.5 mA
100 90 80
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
70 60 50 40 30 20 10 0 0 0.5 1.0 1.5 2.0 2.5 3.0
05715-022
-2 0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
3.5
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
Figure 19. Output Current vs. Receiver Output High Voltage
3.30
Figure 22. Driver Output Current vs. Differential Output Voltage
2.6 2.5
3.25
2.4
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.20
2.3 2.2 2.1 2.0 1.9 1.8
3.15
3.10
3.05
05715-020
1.7 1.6 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
3.00 -40 -30 -20 -10
0
10
20
30
40
50
60
70
80
TEMPERATURE (C)
TEMPERATURE (C)
Figure 20. Receiver Output High Voltage vs. Temperature, IO = 1.5 mA
Figure 23. Driver Differential Output Voltage vs. Temperature, RI = 54
Rev. 0 | Page 9 of 12
05715-023
05715-021
0.1
ADM3493
140 120 1.2 1.1 1.0
OUTPUT CURRENT (mA)
100 80 60 40 20 0
SUPPLY CURRENT (mA)
0.9 0.8 0.7 0.6 0.5 0.4 DE = RE = X*
05715-024
0.3 0.2 -40 -30 -20 -10 0
DE = RE = GND *X = DON'T CARE 10 20 30 40 50 60 70 80
0
2
4
6
8
10
12
OUTPUT VOLTAGE (V)
TEMPERATURE (C)
Figure 24. Output Current vs. Driver Output Low Voltage
-125 -115 -105 100 90 80
Figure 26. Supply Current vs. Temperature
SHUTDOWN CURRENT (nA)
OUTPUT CURRENT (mA)
-95 -85 -75 -65 -55 -45 -35 -25
05715-025
70 60 50 40 30 20 10 0 -10 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
05715-027
-15 -5 -7 -6 -5 -4 -3 -2 -1 0 1 2 3
OUTPUT VOLTAGE (V)
TEMPERATURE (C)
Figure 25. Output Current vs. Driver Output High Voltage
Figure 27. Shutdown Current vs. Temperature, VCC = 3.3 V
Rev. 0 | Page 10 of 12
05715-026
ADM3493 CIRCUIT DESCRIPTION
The ADM3493 is a low power transceiver for RS-485 and RS-422 communications. The ADM3493 can transmit and receive at data rates up to 250 kbps in a half duplex configuration. Driver Enable (DE) and Receiver Enable (RE) pins are included when disabled; the driver and receiver outputs are high impedance. Table 5. Transmitting Truth Table
Transmitting Inputs RE X1 X1 0 1
1 2
LOW POWER SHUTDOWN MODE
A low power shutdown mode is initiated by bringing both RE high and DE low. The ADM3493 does not shut down unless both the driver and receiver are disabled (high impedance). In shutdown, the ADM3493 typically draws only 2 nA of supply current. For the ADM3493, the tPSH and tPSL enable times assume the part was in the low power shutdown mode; the tPZH and tPZL enable times assume the receiver or driver was disabled, but the part was not shut down.
DE 1 1 0 0
DI 1 0 X1 X1
Transmitting Outputs B A 0 1 High-Z2 High-Z2 1 0 High-Z2 High-Z2
Mode
DRIVER OUTPUT PROTECTION
Normal Normal Normal Shutdown
X = Don't care. High-Z = High Impedance.
Table 6. Receiving Truth Table
Receiving Inputs RE 0 0 0 1
1
Two methods are implemented to prevent excessive output current and power dissipation caused by faults or by bus contention. Current limit protection on the output stage provides immediate protection against short circuits over the whole common-mode voltage range (see Typical Performance Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high impedance state if the die temperature rises excessively.
DE 0 0 0 0
A-B +0.2 V -0.2 V Inputs Open X1
Receiving Outputs RO 1 0 1 High-Z2
Mode
PROPAGATION DELAY
Skew time is simply the difference between the low-to-high and high-to-low propagation delay. Small driver/receiver skew times help maintain a symmetrical mark-space ratio (50% duty cycle). The receiver skew time, |tPRLH - tPRHL|, is 20 ns for the ADM3493. The driver skew time is typically under 100 ns.
Normal Normal Normal Shutdown
TYPICAL APPLICATIONS
The ADM3493 transceiver is designed for bidirectional data communications on multipoint bus transmission lines. Figure 22 shows a typical network application's circuits. To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible. The slew rate limited ADM3493 is tolerant of imperfect termination.
ADM3493
A RT B D R RO RE DE
X = Don't care. 2 High-Z = High Impedance
REDUCED EMI AND REFLECTIONS
The ADM3493 is a slew rate limited transceiver, minimizing EMI and reducing reflections caused by improperly terminated cables.
ADM3493
RO RE RT DE DI D B R2 A B R A VCC R1
MAXIMUM NUMBER OF TRANSCEIVERS ON BUS = 256
DI
A
B
ADM3493
ADM3493
R
D
R
D
RO
RE
DE
DI
RO
RE
DE
DI
05715-028
NOTES 1. RT IS EQUAL TO THE CHARACTERISTIC IMPEDANCE OF THE CABLE.
Figure 28. ADM3493 Typical Half Duplex RS-485 Network
Rev. 0 | Page 11 of 12
ADM3493 OUTLINE DIMENSIONS
5.00 (0.1968) 4.80 (0.1890)
8 5
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440)
4 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040)
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) x 45 0.25 (0.0099)
0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE
8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012-AA 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 29. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model ADM3493ARZ1 ADM3493ARZ-REEL71
1
Temperature Range -40C to +85C -40C to +85C
Package Description 8-Lead Standard Small Outline Package [SOIC_N] 8-Lead Standard Small Outline Package [SOIC_N]
Package Options R-8 R-8
Ordering Quantity 1,000
Z = Pb-free part.
(c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05715-0-10/05(0)
Rev. 0 | Page 12 of 12

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