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5 V, 15 kV ESD Protected Half-Duplex, RS-485/RS-422 Transceivers ADM485E/ADM487E/ADM1487E
FEATURES
TIA/EIA RS-485-/RS-422-compliant ESD protection on RS-485 I/O pins 15 kV human body model Data rates ADM487E: 250 kbps ADM485E/ADM1487E: 2.5 Mbps Half-duplex options Reduced slew rates for low EMI -7 V to +12 V common-mode input range Thermal shutdown and short-circuit protection 8-lead SOIC packages
FUNCTIONAL BLOCK DIAGRAM
VCC
ADM485E/ ADM487E/ ADM1487E
RO RE DE DI D
06356-001
R A B
APPLICATIONS
Energy/power metering Lighting systems Industrial control Telecommunications Security systems Instrumentation
GND
Figure 1.
GENERAL DESCRIPTION
The ADM485E/ADM487E/ADM1487E are 5 V, low power data transceivers with 15 kV ESD protection suitable for halfduplex communication on multipoint bus transmission lines. They are designed for balanced data transmission and comply with Telecommunication Industry Association/Electronics Industries Association (TIA/EIA) standards RS-485 and RS-422. The ADM487E and ADM1487E have a 1/4 unit load receiver input impedance that allows up to 128 transceivers on a bus, whereas the ADM485E allows up to 32 transceivers on a bus. Because only one driver is enabled at any time, the output of a disabled or power-down driver is three-stated to avoid overloading the bus. The driver outputs are slew rate-limited to reduce EMI and data errors caused by reflections from improperly terminated buses. Excessive power dissipation caused by bus contention or output shorting is prevented with a thermal shutdown circuit. The parts are fully specified over the industrial temperature ranges and are available in 8-lead SOIC packages.
Table 1. Selection Table
Part Number ADM485E ADM487E ADM1487E Half-/FullDuplex Half Half Half Guaranteed Data Rate (Mbps) 2.5 0.25 2.5 Slew Rate Limited No Yes No Low Power Shutdown No Yes No Driver/Receiver Enable Yes Yes Yes Quiescent Current (A) 300 120 230 Number of Nodes on Bus 32 128 128 Pin Count 8 8 8
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)2007 Analog Devices, Inc. All rights reserved.
ADM485E/ADM487E/ADM1487E 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............................................................ 6 ESD Caution.................................................................................. 6 Pin Configuration and Function Descriptions............................. 7 Typical Performance Characteristics ..............................................8 Test Circuits and Switching Characteristics................................ 11 Theory of Operation ...................................................................... 13 Circuit Description .................................................................... 13 Applications Information .............................................................. 15 Differential Data Transmission ................................................ 15 Cable and Data Rate................................................................... 15 Outline Dimensions ....................................................................... 16 Ordering Guide .......................................................................... 16
REVISION HISTORY
1/07--Revision 0: Initial Version
Rev. 0 | Page 2 of 16
ADM485E/ADM487E/ADM1487E SPECIFICATIONS
VCC = 5 V 5%, TA = TMIN to TMAX, unless otherwise noted. Table 2. ADM485E/ADM487E/ADM1487E
Parameter DRIVER Differential Outputs Differential Output Voltage (no Load) Differential Output Voltage (with Load) |VOD| for Complementary Output States Common-Mode Output Voltage |VOC| for Complementary Output States Logic Inputs Input High Voltage Input Low Voltage Logic Input Current RECEIVER Input Current (A, B) Symbol Min Typ Max Unit Test Conditions/Comments
VOD1 VOD2
5 2 1.5 5 0.2 3 0.2
V V V V V V
RL = 50 (RS-422) RL = 27 (RS-485) (see Figure 18) RL = 27 or 50 (see Figure 18) RL = 27 or 50 (see Figure 18) RL = 27 or 50 (see Figure 18)
VOC
VIH VIL IIN1 IIN2
2.0 0.8 2 1.0 -0.8 0.25 -0.2
V V A mA mA mA mA
DE, DI, RE DE, DI, RE DE, DI, RE DE = 0 V, VIN = 12 V VCC = 0 V or +5.25 V, VIN = -7 V (ADM485E) DE = 0 V, VIN = 12 V VCC = 0 V or +5.25 V, VIN = -7 V (ADM487E/ADM1487E) -7 V < VCM < +12 V VCM = 0 V IOUT = -4 mA, VID = +200 mV IOUT = +4 mA, VID = -200 mV 0.4 V < VO < 2.4 V -7 V < VCM < +12 V (ADM485E) -7 V< VCM < +12 V (ADM487E/ADM1487E) RE = 0 V or VCC, DE = VCC (ADM485E) RE = 0 V or VCC, DE = 0 V (ADM485E) RE = 0 V or VCC, DE = VCC (ADM1487E) RE = 0 V or VCC, DE = 0 V (ADM1487E) RE = 0 V or VCC, DE = VCC (ADM487E) RE = 0 V, DE = 0 V (ADM487E) DE = 0 V, RE = VCC (ADM487E) -7 V VO +12 V, applies to peak current -7 V VO +12 V, applies to peak current 0 V VO VCC Human body model
Differential Inputs Differential Input Threshold Voltage Input Hysteresis Receiver Output Logic Output Voltage High Output Voltage Low Three-State Output Leakage Current Receiver Input Resistance POWER SUPPLY No Load Supply Current
VTH VTH VOH VOL IOZR RIN
-0.2 70 3.5
+0.2
V mV V V A k k A A A A A A A mA mA kV
0.4 1 12 48 500 300 300 230 250 120 0.5 35 35 7 15 900 500 500 400 400 250 10 250 250 95
ICC
Supply Current in Shutdown Driver Short-Circuit Current, VO High Driver Short-Circuit Current, VO Low Receiver Short-Circuit Current ESD PROTECTION A, B Pins
ISHDN IOSD1 IOSD2 IOSR
Rev. 0 | Page 3 of 16
ADM485E/ADM487E/ADM1487E
TIMING SPECIFICATIONS
VCC = 5 V 5%, TA = TMIN to TMAX, unless otherwise noted. Table 3. ADM485E/ADM1487E
Parameter DRIVER Input to Output Symbol tDPLH tDPHL Output Skew to Output Rise/Fall Time Enable Time to High Level Enable Time to Low Level Disable Time from Low Level Disable Time from High Level RECEIVER Input to Output |tPLH - tPHL| Differential Receiver Skew Enable Time to Low Level Enable Time to High Level Disable Time from Low Level Disable Time from High Level MAXIMUM DATA RATE tSKEW tDR, tDF tDZH tDZL tDLZ tDHZ tRPLH tSKEW tRZL tRZL tRLZ tRHZ fMAX 20 3 Min 10 10 Typ 40 40 5 20 45 45 45 45 60 5 25 20 20 20 2.5 50 50 50 50 Max 60 60 10 40 70 70 70 70 200 Unit ns ns ns ns ns ns ns ns ns ns ns ns ns ns Mbps Test Conditions/Comments RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) CRL = 100 pF, S2 closed (see Figure 21) CRL = 100 pF, S1 closed (see Figure 22) CRL = 15 pF, S1 closed (see Figure 22) CRL = 15 pF, S2 closed (see Figure 21) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 23 and Figure 24) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 4 and Figure 5) CRL = 15 pF, S2 closed (see Figure 25) CRL = 15 pF, S1 closed (see Figure 25) CRL = 15 pF, S2 closed (see Figure 25) tPLH, tPHL < 50% of data period
Rev. 0 | Page 4 of 16
ADM485E/ADM487E/ADM1487E
VCC = 5 V 5%, TA = TMIN to TMAX, unless otherwise noted. Table 4. ADM487E
Parameter DRIVER Input to Output Symbol tDPLH tDPHL Output Skew to Output Rise/Fall Time Enable Time to High Level Enable Time to Low Level Disable Time from Low Level Disable Time from High Level RECEIVER Input to Output tSKEW tDR, tDF tDZH tDZL tDLZ tDHZ tRPLH tRPHL tSKEW tRZL tRZL tRLZ tRHZ fMAX tDZH(SHDN) tDZL(SHDN) tRZL(SHDN) tRZH(SHDN) Min 250 250 250 250 250 300 300 250 250 100 25 25 25 25 250 50 200 5000 5000 5000 50 50 50 50 600 Typ 800 800 20 Max 2000 2000 800 2000 2000 2000 3000 3000 2000 2000 Unit ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns kbps ns ns ns ns Test Conditions/Comments RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) CRL = 100 pF, S2 closed (see Figure 21) CRL = 100 pF, S1 closed (see Figure 22) CRL = 15 pF, S1 closed (see Figure 22) CRL = 15 pF, S2 closed (see Figure 21) RDIFF = 54 , CL1 = CL2 = 100 pF RDIFF = 54 , CL1 = CL2 = 100 pF (see Figure 19 and Figure 20) CRL = 15 pF, S1 closed (see Figure 23 and Figure 24) CRL = 15 pF, S2 closed (see Figure 25) CRL = 15 pF, S1 closed (see Figure 25) CRL = 15 pF, S2 closed (see Figure 25) tPLH, tPHL < 50% of data period CL = 100 pF, S2 closed (see Figure 21) CL = 100 pF, S1 closed (see Figure 22) CL = 15 pF, S2 closed (see Figure 25) CL = 15 pF, S1 closed (see Figure 25)
|tPLH - tPHL| Differential Receiver Skew Enable Time to Low Level Enable Time to High Level Disable Time from Low Level Disable Time from High Level Maximum Data Rate Time to Shutdown 1 Driver Enable from Shutdown to Output High Driver Enable from Shutdown to Output Low Receiver Enable from Shutdown to Output High
1
The ADM487E is put into shutdown mode by bringing the RE high and the DE low. If the inputs are in this state for less than 50 ns, the parts are guaranteed not to enter shutdown. If the inputs are in this state for at least 600 ns, the ADM487E is guaranteed to enter shutdown.
Rev. 0 | Page 5 of 16
ADM485E/ADM487E/ADM1487E ABSOLUTE MAXIMUM RATINGS
TA = 25C, unless otherwise noted. Table 5.
Parameter VCC to GND Digital I/O Voltage (DE, RE) Driver Input Voltage (DI) Receiver Output Voltage (RO) Driver Output/Receiver Input Voltage (A, B) Operating Temperature Range Storage Temperature Range JA Thermal Impedance SOIC-8 Lead Temperature Soldering (10 sec) Rating -0.5 V to +6 V -0.5 V to (VCC + 0.5 V) -0.5 V to (VCC + 0.5 V) -0.5 V to (VCC + 0.5 V) -9 V to +14 V -40 to +85C -65 to +150C 158C/W
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
260C
Rev. 0 | Page 6 of 16
ADM485E/ADM487E/ADM1487E PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
RO 1 RE 2 DE 3 DI 4
ADM485E/ ADM487E/ ADM1487E
TOP VIEW (Not to Scale)
8 7 6 5
VCC B A
06356-002
GND
Figure 2. Pin Configuration
Table 6. Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 Mnemonic RO RE DE DI GND A B VCC 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 RO; a high level places it in a high impedance state. Driver Output Enable. A high level enables the driver differential outputs, Pin A and Pin B; a low level places it in a high impedance state. Driver Input. When the driver is enabled, a Logic L = low on DI forces A low and B high; a Logic H = high on DI forces Pin A high and Pin B low. Ground Connection (0 V). Noninverting Receiver Input A/Driver Output A. Inverting Receiver Input B/Driver Output B. Power Supply (5 V 5%).
Rev. 0 | Page 7 of 16
ADM485E/ADM487E/ADM1487E TYPICAL PERFORMANCE CHARACTERISTICS
50 45
OUTPUT LOW VOLTAGE (V)
0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2
06356-019
40
OUTPUT CURRENT (mA)
35 30 25 20 15 10
06356-016
IRO = 8mA
5 0 0 0.5 1.0 1.5 2.0
0.1 0 -40 -20 0 20 40 60 80
2.5
OUTPUT LOW VOLTAGE (V)
TEMPERATURE (C)
Figure 3. Output Current vs. Receiver Output Low Voltage
-30
Figure 6. Receiver Output Low Voltage vs. Temperature
45 40
-25 35
OUTPUT CURRENT (mA)
-20
OUTPUT CURRENT (mA)
06356-017
30 25 20 15 10
-15
-10
-5
06356-020
5 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
0 1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
OUTPUT HIGH VOLTAGE (V)
DIFFERENTIAL OUTPUT VOLTAGE (V)
Figure 4. Output Current vs. Receiver Output High Voltage
4.5 DIFFERENTIAL OUTPUT VOLTAGE (V)
Figure 7. Driver Output Current vs. Differential Output Voltage
2.3 2.2 2.1 2.0 1.9 1.8 1.7
06356-021
4.4
OUTPUT HIGH VOLTAGE (V)
4.3
4.2
IRO = -8mA
4.1
4.0
06356-018
1.6 1.5 -40
3.9 -40
-20
0
20
40
60
80
-20
0
20
40
60
80
TEMPERATURE (C)
TEMPERATURE (C)
Figure 5. Receiver Output High Voltage vs. Temperature
Figure 8. Driver Differential Output Voltage vs. Temperature
Rev. 0 | Page 8 of 16
ADM485E/ADM487E/ADM1487E
140 120
600
500
OUTPUT CURRENT (mA)
SUPPLY CURRENT (A)
100 80 60 40 20 0
400
300
200 DE = VCC AND RE = X 100
06356-022
0
2
4
6
8
10
12
0 -40
DE = 0 AND RE = O -20 0 20 40 60 80 TEMPERATURE (C)
OUTPUT LOW VOLTAGE (V)
Figure 9. Output Current vs. Driver Output Low Voltage
-140 -120
Figure 12. ADM487E Supply Current vs. Temperature
10 9 8
SHUTDOWN CURRENT (A)
OUTPUT CURRENT (mA)
-100 -80 -60 -40 -20 0 -8
7 6 5 4 3 2 1 0 -60 -40 -20 0 20 40 60 80
06356-026
06356-023
-6
-4
-2
0
2
4
6
100
OUTPUT HIGH VOLTAGE (V)
TEMPERATURE (C)
Figure 10. Output Current vs. Driver Output High Voltage
600
3
Figure 13. Shutdown Current vs. Temperature
T
B
500 SUPPLY CURRENT (A)
400
300
DE = VCC AND RE = X
2
A
200
DE = 0 AND RE = X
06356-024
1
RO CH1 5.00V CH2 500mV CH3 500mV M200ns T 57.60% A CH1 2.80V
0 -40
-20
0
20
40
60
80
TEMPERATURE (C)
Figure 11. ADM485E/ADM1487E Supply Current vs. Temperature
Figure 14. ADM487E Receiver tPHL
Rev. 0 | Page 9 of 16
06356-027
100
06356-025
ADM485E/ADM487E/ADM1487E
T 3
A
3
T
B
2
B
2
A
RO
06356-028
RO CH1 5.00V CH2 500mV CH3 500mV M20ns T 60.80% A CH1 2.70V
CH1 5.00V CH2 500mV CH3 500mV
M200ns T 60.80%
A CH1
2.80V
Figure 15. ADM487E Receiver tPLH Driven by External RS-485 Device
T 3
Figure 17. ADM485E/ADM1487E Receiver tPLH
A
2
B
RO
06356-029
1
CH1 5.00V CH2 500mV CH3 500mV
M20ns T 60.80%
A CH1
2.70V
Figure 16. ADM485E/ADM1487E Receiver tPHL
Rev. 0 | Page 10 of 16
06356-030
1
1
ADM485E/ADM487E/ADM1487E TEST CIRCUITS AND SWITCHING CHARACTERISTICS
Y RL VOD
VCC S1
RL VOC
06356-003
RL = 500 OUT
0V OR 5V
D
CL
Z
Figure 18. Driver DC Test Load
VDD DE CL A DI B VOD RL CL
06356-004
GENERATOR
50
5V DE VCC/2 0V
tDZL(SHDN)
VCC OUT VOL
tDZL,
tDLZ
2.3V
06356-007
0.5V
Figure 19. Driver Timing Test Circuit
Figure 22. Driver Enable and Disable Times (tDZL, tDLZ, tDZL(SHDN))
B RECEIVER OUTPUT R A
06356-008
5V DI 0V 1.5V
ATE
VID
tDPLH
tDPHL
1/2 VO
Figure 23. Receiver Propagation Delay Test Circuit
B A VO 1/2VO VDIFF VO 20% VDIFF = V (A) - V (B) 80% 80% 20%
06356-005
A B
+1V -1V
tRPLH
tRPHL
0V -VO
tSKEW = tDPLH - tDPHL
VOL THE RISE TIME AND FALL TIME OF INPUT A AND INPUT B < 4ns
Figure 20. Driver Propagation Delays
Figure 24. Receiver Propagation Delays
S1 0 OR 5V D CL OUT RL = 500
GENERATOR
50
5V DE 1.5V 0V 0.5V 2.3V VOH
tDZH, tDZH(SHDN)
OUT
tDHZ
0V
Figure 21. Driver Enable and Disable Times (tDHZ, tDZH, tDZH(SHDN))
Rev. 0 | Page 11 of 16
06356-006
06356-009
tDR
tDF
RO
VOH 1.5V
ADM485E/ADM487E/ADM1487E
+1.5V -1.5V 0V OR 5V S3 VID 1k CL 15pF S1 VCC
S2
GENERATOR
50
S1 OPEN S2 CLOSED S3 = +1.5V +5V RE 0V RE
S1 CLOSED S2 OPEN S3 = -1.5V +5V +1.5V 0V
tRZL, tRZL(SHDN)
tRZH, tRZH(SHDN)
RO
VOH +1.5V 0V RO
VCC +1.5V VOL S1 CLOSED S2 OPEN S3 = +1.5V
S1 OPEN S2 CLOSED S3 = +1.5V +5V RE +1.5V 0V RE
+5V +1.5V 0V
tRHZ
VOH RO 0V
tRLZ
VCC
06356-010
RO
+0.5V
+0.5V
VOL
Figure 25. Receiver Enable and Disable Times
Rev. 0 | Page 12 of 16
ADM485E/ADM487E/ADM1487E THEORY OF OPERATION
The ADM485E/ADM487E/ADM1487E are ruggedized RS-485 transceivers that operate from a single 5 V supply. They contain protection against high levels of electrostatic discharge and are ideally suited for operation in electrically harsh environments or where cables can be plugged or unplugged. These devices are intended for balanced data transmission and comply with TIA/ EIA standards RS-485 and RS-422. They contain a differential line driver and a differential line receiver and are suitable for half-duplex data transmission, as the driver and receiver share the same differential pins. The input impedance on the ADM485E is 12 k, allowing up to 32 transceivers on the differential bus. The ADM487E/ ADM1487E are 48 k, allowing up to 128 transceivers on the differential bus.
5V 0.1F RE
RO B
5V 0.1F VCC
DE DI
VCC
ADM485E/ ADM487E/ ADM1487E
DI DE
B A A
ADM485E/ ADM487E/ ADM1487E
RS485/RS-422 LINK
RO GND
GND
RE
06356-012
CIRCUIT DESCRIPTION
The ADM485E/ADM487E/ADM1487E are operated from a single 5 V 10% power supply. Excessive power dissipation caused by bus contention or output shorting is prevented by a thermal shutdown circuit. If, during fault conditions, a significant temperature increase is detected in the internal driver circuitry, this feature forces the driver output into a high impedance state. The receiver contains a fail-safe feature that results in a logic high output state if the inputs are unconnected (floating). A high level of robustness is achieved using internal protection circuitry, eliminating the need for external protection components such as tranzorbs or surge suppressors. Low electromagnetic emissions are achieved using slew-ratelimited drivers, minimizing both conducted and radiated interference. The ADM485E/ADM487E/ADM1487E can transmit at data rates up to 250 kbps. A typical application for the ADM485E/ADM487E/ADM1487E is illustrated in Figure 26, which shows a half-duplex link where data can be transferred at rates up to 250 kbps. A terminating resistor is shown at both ends of the link. This termination is not critical, because the slew rate is controlled by the ADM485E/ ADM487E/ADM1487E and reflections are minimized. The communications network can be extended to include multipoint connections, as shown in Figure 29. As many as 32 ADM485E transceivers or 128 ADM487E/ADM1487E transceivers can be connected to the bus.
Figure 26. Typical Half-Duplex Link Application
Table 7 and Table 8 show the truth tables for transmitting and receiving. Table 7. Transmitting Truth Table
RE X1 X1 0 1
1
Transmitting Inputs DE DI 1 1 0 0 1 0 X1 X1
Transmitting Outputs B A 0 1 High-Z High-Z 1 0 High-Z High-Z
X = don't care.
Table 8. Receiving Truth Table
RE 0 0 0 1
1
Receiving Inputs DE 0 0 0 0
A to B
Receiving Outputs RO 1 0 1 High-Z
+0.2 V -0.2 V Inputs Open Circuit X1
X = don't care.
ESD Transient Protection Scheme
The ADM485E/ADM487E/ADM1487E use protective clamping structures on their inputs and outputs that clamp the voltage to a safe level and dissipate the energy present in ESD (electrostatic). The protection structure achieves ESD protection up to 15 kV human body model (HBM).
Rev. 0 | Page 13 of 16
ADM485E/ADM487E/ADM1487E
ESD Testing
Two coupling methods are used for ESD testing: contact discharge 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; hence 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 as a result of arcing or heating. Even if catastrophic failure does not occur immediately, the device can suffer from parametric degradation, which can result in degraded performance. The cumulative effects of continuous exposure can eventually lead to complete failure.
HIGH VOLTAGE GENERATOR C1 R2 DEVICE UNDER TEST R2 15kV C1 100pF
06356-013
The ESD discharge can induce latch-up in the device under test. Therefore, it is important that ESD testing on the I/O pins be carried out while device power is applied. This type of testing is more representative of a real-world I/O discharge where the equipment is operating normally when the discharge occurs.
100% 90%
IPEAK
36.8% 10%
06356-014
TIME (t)
tRL
tDL
Figure 28. Human Body Model ESD Current Waveform
Table 9. ADM483E ESD Test Results
ESD Test Method Human Body Model (HBM) I/O Pins 15 kV Other Pins 3.5 V
ESD TEST METHOD HUMAN BODY MODEL
Figure 27. ESD Generator
I/O lines are particularly vulnerable to ESD damage. Simply touching or plugging in an I/O cable can result in a static discharge that can damage or completely destroy the inter face product connected to the I/O port. It is, therefore, extremely important to have high levels of ESD protection on the I/O lines.
Rev. 0 | Page 14 of 16
ADM485E/ADM487E/ADM1487E APPLICATIONS INFORMATION
DIFFERENTIAL DATA TRANSMISSION
Differential data transmission is used to reliably transmit 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 TIA/EIA that specify the electrical characteristics of transceivers used in differential data transmission. The RS-422 standard specifies data rates up to 10 MB and line lengths up to 4000 feet. A single driver can drive a transmission line with up to 10 receivers. To cater to true multipoint communications, the RS-485 standard is defined. This standard meets or exceeds all the requirements of RS-422, but also allows for 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 RS-422 and RS-485 is that the drivers can be disabled, thereby allowing as many as 32 drivers to be connected to a single line. Only one driver is 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
The transmission line of choice for RS-485 communications is a twisted pair. A twisted pair cable can cancel common-mode noise and can also cause cancellation of the magnetic fields generated by the current flowing through each wire, thereby reducing the effective inductance of the pair. A typical application showing a multipoint transmission network is illustrated in Figure 29. An RS-485 transmission line can have as many as 32 transceivers on the bus. Only one driver can transmit at a particular time, but multiple receivers can be enabled simultaneously.
RT RT
D
D
R
R
Figure 29. Typical RS-485 Network
Rev. 0 | Page 15 of 16
06356-015
D
R
D
R
ADM485E/ADM487E/ADM1487E OUTLINE DIMENSIONS
5.00 (0.1968) 4.80 (0.1890)
4.00 (0.1574) 3.80 (0.1497)
8 1
5 4
6.20 (0.2440) 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 30. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model ADM485EARZ 1 ADM485EARZ-REEL71 ADM487EARZ1 ADM487EARZ-REEL71 ADM1487EARZ1 ADM1487EARZ-REEL71
1
Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
Package Description 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N)
060506-A
Package Option R-8 R-8 R-8 R-8 R-8 R-8
Z = Pb-free part.
(c)2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06356-0-1/07(0)
Rev. 0 | Page 16 of 16

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