AD ADM3088 High-speed (10mbps), fail-safe, rs-485/rs-422 transceivers with slew-rate-limiting and 5kv esd protection Datasheet

PRELIMINARY TECHNICAL DATA
High-Speed (10Mbps), Fail-Safe, RS-485/RS-422
Transceivers with Slew-Rate-Limiting
and ±15kV ESD Protection
ADM3082/ADM3085/ADM3088
a
FEATURES
Enhanced Slew Rate Limiting for Error-Free Data
Transmission
GENERAL DESCRIPTION
The ADM3082/ADM3085/ADM3088 are high-speed
RS-485/RS-422 transceivers consisting of one driver and one
receiver per package. The devices feature fail-safe operation,
ensuring a logic-high receiver output when the receiver inputs are open-circuit or short-circuit. This guarantees that
the receiver output will be high if all the transmitters on a
terminated bus are disabled (high-impedance).
Fail-Safe Receiver Operation while Maintaining
EIA/TIA-485 compatibility
Low-Current (1nA) Shutdown Mode
High Input Impedance — Up to 256 Transceivers on Bus
±15kV ESD Protection (Human Body Model) on
RS-485 I/O pins
The ADM3082 has a slew-rate limited driver to minimize
electromagnetic interference (EMI) and reduce reflections
caused by incorrectly terminated cables. This allows errorfree transmission at data rates up to 115kbps.
Pin-Compatible with Industry Standard 75176
APPLICATIONS
Enhanced Replacement for Industry-Standard Parts
EMI-Sensitive Systems
Level Translation
LANs for Industrial Control Applications
The ADM3085 offers a higher slew rate allowing data rates
up to 500kbps, while the ADM3088 has a driver whose slew
rate is not limited, allowing data rates up to 10Mbps.
All devices in the family feature ±15kV electrostatic discharge (ESD) protection and high receiver input impedance (1/8 unit load), allowing up to 256 transceivers on
the bus. The devices have low current drain of 375µA unloaded, or fully loaded with the drivers disabled, and feature an ultra-low power (1nA) shutdown mode.
FUNCTIONAL BLOCK DIAGRAM
RO
1
RE
2
DE
3
DI
4
8
VCC
7
B
6
A
5
G ND
R
D
AD M 30 82/A D M 308 5/AD M 3088
REV. PrA 02/02
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 2002
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 SPECIFICATIONS
DC ELECTRICAL CHARACTERISTICS
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1)
DRIVER
Parameter
Min
Typ
Differential Driver Output, V OD1
Differential Driver Output,VOD2
5
Driver Common-Mode
Output Voltage, VOC
Change-in-Magnitude of
Common-Mode Voltage, DVOC
Figure 1 (No Load)
V
V
Figure 1, R = 50V (RS-422)
Figure 1, R = 27V (RS-485)
0.2
V
Figure 1, R = 50V or R = 27V
(Note 2)
3
V
Figure 1, R = 50V or R = 27V
0.2
V
Figure 1, R = 50V or R = 27V
(Note 2)
2.0
V
Input Low Voltage, VlL1
(DE, DI, RE)
0.8
DI Input Hysteresis, VHYS
Units Test Conditions/Comments
V
2.0
1.5
Change-in-Magnitude of Differential
Common-Mode Output Voltage, DV OD
Input High Voltage,VIH1
(DE, DI, RE)
Max
100
V
mV
Input Current, IIN1 (DE, DI, RE)
±2
µA
Input Current (A and B), IIN4
125
µA
–75
µA
125
µA
Output Leakage (Y and Z),
Full Duplex, IO
Driver Short-Circuit,V OD1
DE
VIN
DE
VIN
=
=
=
=
GND, VCC = GND or 5.25V,
12V
GND, VCC = GND or 5.25V,
–7V
DE
VIN
DE
VIN
=
=
=
=
GND, VCC = GND or 5.25V,
12V
GND, VCC = GND or 5.25V,
–7V
–100
µA
–250
mA
–7V # VOUT # VCC (Note 3)
mA
mA
0V # VOUT # 12V (Note 3)
0V # VOUT # VCC (Note 3)
Output Current
250
±25
–2–
REV. PrA 02/02
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued)
DC ELECTRICAL CHARACTERISTICS
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1)
RECEIVER
Parameter
Min
Typ
Max
Receiver Differential Threshold
Voltage, VTH
–200
–125
–50
Receiver Input Hysteresis, DVTH
Receiver Output High Voltage, VOH
25
Units Test Conditions/Comments
mV
–7V # VCM # 12V
mV
VCC –1 .5
V
IO = -4mA, VID = -50mV
Receiver Output Low Voltage, VOL
0.4
V
IO = 4mA, VID = -200mV
Three-State Output Current at
Receiver, IOZR
±1
µA
0.4V # VO # 2.4V
kV
–7V # VCM # 12V
mA
0V # VRO # VCC
Receiver Input Resistance, RIN
96
Receiver Output Short-Circuit
Current, IOSR
±7
±95
SUPPLY CURRENT
Parameter
Supply Current, ICC
Supply Current in
Shutdown Mode, ISHDN
ESD Protection for Y, Z, A, B
Min
Typ
Max
430
900
µA
375
600
µA
0.001
10
µA
DE = GND, VRE = VCC
kV
Human Body Model
±15
Units Test Conditions/Comments
No
DE
No
DE
load, RE = DI = GND or VCC,
= VCC
load, RE = DI = GND or VCC,
= GND
NOTES
1
All currents into the device are positive; all currents out of the device are negative. All voltages are referred to device ground unless otherwise noted.
DDO and DVCC are the changes in VOD and VOC, respectively, when the DI input changes state.
3
Maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during current limiting.
2
REV. PrA 02/02
–3–
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued)
SWITCHING CHARACTERISTICS—ADM3082
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1)
Parameter
Min
Typ
Max
Driver Input-to-Output, tDPLH
Driver Input-to-Output, tDPHL
500
500
2030
2030
2600
2600
ns
ns
Figures 2 and 3, RDIFF = 54V,
CL1 = CL2 = 100pF
–3
±200
ns
Figures 2 and 3, RDIFF = 54V,
CL1 = CL2 = 100pF
1320
2500
ns
Figures 2 and 3, RDIFF = 54V,
CL1 = CL2 = 100pF
Driver Output Skew,|tDPLH-tDPHL|, tDSKEW
Driver Rise or Fall Time, tDR, tDF
667
Maximum Data Rate, fMAX
115
Units Test Conditions/Comments
kbps
Driver Enable to Output High, tDZH
3500
ns
Figures 5 and 6, CL = 100pF,
S2 closed
Driver Enable to Output Low, tDZL
3500
ns
Figures 5 and 6, CL = 100pF,
S1 closed
Driver Disable Time from Low, tDLZ
100
ns
Figures 5 and 6, CL = l5pF,
S1 closed
Driver Disable Time from High, tDHZ
100
ns
Figures 4 and 5, CL = l5pF,
S2 closed
127
200
ns
Figure 7; |VID| $ 2.0V;
rise and fall time of VID # l5ns
Differential Receiver Skew, tRSKD
|tRPLH - tRPHL|
3
±30
ns
Figure 7; |VID| $ 2.0V;
rise and fall time of VID # l5ns
Receiver Enable to Output Low, tRZL
20
50
ns
Figures 7 and 8; CL = 100pF,
S1 closed
Receiver Enable to Output High, tRZH
20
50
ns
Figures 7 and 8, CL = 100pF,
S2 closed
Receiver Disable Time from Low, tRLZ
20
50
ns
Figures 7 and 8, CL = 100pF,
S1 closed
Receiver Disable Time from High, tRHZ
20
50
ns
Figures 7 and 8 CL = 100pF,
S2 closed
200
600
ns
(Note 5)
Driver Enable from Shutdown to
Output High, tDZH(SHDN)
6000
ns
Figures 5 and 6, CL = l5pF,
S2 closed
Driver Enable from Shutdown to
Output Low, tDZL(SHDN)
6000
ns
Figures 5 and 6, CL = l5pF,
S1 closed
Receiver Enable from Shutdown
to Output High, tRZH(SHDN)
3500
ns
Figures 7 and 8, CL = 100pF,
S2 closed
Receiver Enable from Shutdown
to Output Low, tRZL(SHDN)
3500
ns
Figures 7 and 8, CL = 100pF,
S1 closed
Receiver Input to Output, tRPLH, tRPHL
Time to Shutdown, tSHDN
50
–4–
REV. PrA 02/02
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued)
SWITCHING CHARACTERISTICS—ADM3085
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1)
Parameter
Min
Typ
Max
Driver Input-to-Output, tDPLH
Driver Input-to-Output, tDPHL
250
250
720
720
1000
1000
ns
ns
Figures 2 and 3 RDIFF = 54V,
CL1 = CL2 = 100pF
–3
±100
ns
Figures 2 and 3, RDIFF = 54V,
CL1 = CL2 = 100pF
530
750
ns
Figures 2 and 3, RDIFF = 54V,
CL1 = CL2 = 100pF
Driver Output Skew,|tDPLH - tDPHL|, tDSKEW
Driver Rise or Fall Time, tDR, tDF
200
Maximum Data Rate, fMAX
500
Units Test Conditions/Comments
kbps
Driver Enable to Output High, tDZH
2500
ns
Figures 5 and 6, CL = 100pF,
S2 closed
Driver Enable to Output Low, tDZL
2500
ns
Figures 5 and 6, CL = 100pF,
S1 closed
Driver Disable Time from Low, tDLZ
100
ns
Figures 5 and 6, CL = l5pF,
S1 closed
Driver Disable Time from High, tDHZ
100
ns
Figures 5 and 6, CL = l5pF,
S2 closed
127
200
ns
Figure 7; |VID| $ 2.0V;
rise and fall time of VID # l5ns
Differential Receiver Skew, tRSKD
|tRPLH - tRPHL|
3
±30
ns
Figure 7; |VID| $ 2.0V;
rise and fall time of VID # l5ns
Receiver Enable to Output Low, tRZL
20
50
ns
Figures 7 and 8 CL = 100pF,
S1 closed
Receiver Enable to Output High, tRZH
20
50
ns
Figures 7 and 8, CL = 100pF,
S2 closed
Receiver Disable Time from Low, tRLZ
20
50
ns
Figures 7 and 8, CL = 100pF,
S1 closed
Receiver Disable Time from High, tRHZ
20
50
ns
Figures 7 and 8, CL = 100pF,
S2 closed
200
600
ns
(Note 5)
Driver Enable from Shutdown
to Output High, tDZH(SHDN)
4500
ns
Figures 5 and 6, CL = l5pF,
S2 closed
Driver Enable from Shutdown
to Output Low, tOZL(SHDN)
4500
ns
Figures 5 and 6, CL = l5pF,
S1 closed
Receiver Enable from Shutdown
to Output High, tRZH(SHDN)
3500
ns
Figures 7 and 8, CL = 100pF,
S2 closed
Receiver Enable from Shutdown
to Output Low, tRZL(SHDN)
3500
ns
Figures 7 and 8, CL = 100pF,
S1 closed
Receiver Input to Output, tRPLH, tRPHL
Time to Shutdown, tSHDN
REV. PrA 02/02
50
–5–
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued)
SWITCHING CHARACTERISTICS—ADM3088
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1)
Parameter
Min
Driver Input-to-Output, tDPLH
Driver Input-to-Output, tDPHL
Driver Output Skew,|tDPLH -tDPHL|, tDSKEW
Driver Rise or Fall Time, tDR, tDF
Maximum Data Rate, fMAX
Typ
Max
34
34
60
60
ns
ns
Figures 2 and 5, RDIFF = 54V,
CL1 = CL2 = 100pF
–2.5
±10
ns
Figures 2 and 5, RDIFF = 54V,
CL1 = CL2 = 100pF
14
25
ns
Figures 7 and 9, RDIFF = 54V,
CL1 = CL2 = 100pF
10
Units Test Conditions/Comments
Mbps
Driver Enable to Output High, tDZH
150
ns
Figures 5 and 6, CL = 100pF,
S2 closed
Driver Enable to Output Low, tDZL
150
ns
Figures 5 and 6, CL = 100pF,
S1 closed
Driver Disable Time from Low, tDLZ
100
ns
Figures 5 and 6, CL = l5pF,
S1 closed
Driver Disable Time from High, tDHZ
100
ns
Figures 5 and 6, CL = l5pF,
S2 closed
106
150
ns
Figure 7; |VID| $ 2.0V;
rise and fall time of VID # l5ns
DifferentialReceiver Skew, tRSKD
|tRPLH – tRPHL|
0
±10
ns
Figures 7; |VID| $ 2.0V;
rise and fall time of VID # l5ns
Receiver Enable to Output Low, tRZL
20
50
ns
Figures 7 and 8, CL = 100pF,
S1 closed
Receiver Enable to Output High, tRZH
20
50
ns
Figures 7 and 8, CL = 100pF,
S2 closed
Receiver Disable Time from Low, tRLZ
20
50
ns
Figures 7 and 8, CL = 100pF,
S1 closed
Receiver Disable Time from High, tRHZ
20
50
ns
Figures 7 and 8, CL = 100pF,
S2 closed
200
600
ns
(Note 5)
Driver Enable from Shutdown
toOutput High, tDZH(SHDN)
250
ns
Figures 5 and 6, CL = l5pF,
S2 closed
Driver Enable from Shutdown
to Output Low, tDZL(SHDN)
250
ns
Figures 5 and 6, CL = l5pF,
S1 closed
Receiver Enable from Shutdown
to Output High, tRZH(SHDN)
3500
ns
Figures 7 and 8, CL = 100pF,
S2 closed
Receiver Enable from Shutdown
to Output Low, tRZL(SHDN)
3500
ns
Figures 7 and 8, CL = 100pF,
S1 closed
Receiver Input-to-Output, tRPLH, tRPHL
Time to Shutdown, tSHDN
50
NOTES
The device is put into shutdown by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 600ns, the device is guaranteed to have entered shutdown.
5
–6–
REV. PrA 02/02
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 TEST CIRCUITS AND TIMING
VCC
Y
R
VOD
TEST
P O INT
R
S1
Z
VOC
500 V
O UT P UT
UN D E R
TEST
CR L
S2
15p F
Figure 1. Driver DC Load Test Circuit
3V
Figure 5. Test Load for Driver Enable/Disable Time Test
DE
5V
CL 1
DE
1.5V
DI
VOD2
0V
R D IFF
tDL Z
tDZL(S HD N) , t DZL
CL2
Y, Z
V OL
2.3V
O U T PU T N O R M A LL Y HIG H
Y, Z
Figure 2. Test Load for Driver Timing Tests
V OL
V O L+0.5V
O U T PU T N O R M A LL Y L O W
V O H -0.5V
2.3V
t DH Z
t DZH (SH DN ) t DZH
Figure 6. Driver Enable and Disable Times
5V
DI
1.5V
0V
tDP LH
t DP H L
VCC
Z
V0
Y
V 0 /2
TEST
P O INT
V DIFF = V Y - V Z
V DIFF
V0
0
90%
90%
1k V
10%
10%
-V 0
S1
t DR
t DF
t S KE W = |t DP LH -tDP H L |
RO
Figure 3. Driver Propagation Delays
CRL
15p F
S2
1k V
A 1V
B -1 V
t RP HL
VOH
tRP LH
Figure 7. Test Load for Receiver Enable/Disable Time Test
1 .5 V
RO
VOL
Figure 4. Receiver Propagation Delays
5V
RE
1.5V
0V
V CC
RO
RO
t RZ L (S HDN ) , t RZ L
1.5V
1.5V
t RL Z
V O L +0.5V
O UT PU T NO R M A LL Y L O W
O UT PU T NO R M A LL Y HIG H
0V
t R ZH(S HD N) , t R ZH
V O H -0.5V
t R HZ
Figure 8. Receiver Enable and Disable Delay Times
REV. PrA 02/02
–7–
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . +7V
Logic Input Voltage . . . . . . . . . . . . –0.3V to (V CC+0.3V)
Driver Output Voltage (A, B) . . . . . . . . . . . . . . . . . . ±13V
Receiver Input Voltage (A, B) . . . . . . . . . . . . . . . . . . ±13V
Receiver Input Voltage, Full Duplex (A, B) . . . . . . ±13V
Receiver Output Voltage (RO) . . . –0.3V to (V CC+0.3V)
Continuous Power Dissipation
8-Pin Plastic DIP
(derate 9.09mW/oC above +70oC) . . . . . . . . . . . 727mW
8-Pin Plastic SO
(derate 5.88mW/oC above +70oC) . . . . . . . . . . . 471mW
Maximum Junction Temperature (T J max) . . . . . . . 150 °C
Storage Temperature Range . . . . . . . . . –65°C to +150°C
Lead Temperature, Soldering
Vapor Phase 60 sec . . . . . . . . . . . . . . . . . . . . . . . . . +215°C
Infra-Red 15 sec . . . . . . . . . . . . . . . . . . . . . . . . . . . +200°C
RO
1
RE
2
DE
3
DI
4
AD M 30 88/
AD M 30 85/
AD M 30 88
T O P V IE W
(No t to S cale)
ORDERING
*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 CHARACTERISTICS
8-Pin Plastic DIP Package
θJA = tbd K/Watt, θJC = tbd K/Watt
8-Pin Plastic SO Package
θJA = tbd K/Watt, θJC = tbd K/Watt
8
VCC
7
B
6
A
5
G ND
INFORMATION
Model
Temperature Range
Package Option
ADM3082JN
0°C to +70°C
8 Pin Plastic DIP
ADM3082JR
0°C to +70°C
8 Pin SO
ADM3082AN –40°C to +85°C
8 Pin Plastic DIP
ADM3082AR
–40°C to +85°C
8 Pin SO
ADM3085JN
0°C to +70°C
8 Pin Plastic DIP
ADM3085JR
0°C to +70°C
8 Pin SO
ADM3085AN –40°C to +85°C
8 Pin Plastic DIP
ADM3085AR
–40°C to +85°C
8 Pin SO
ADM3088JN
0°C to +70°C
8 Pin Plastic DIP
ADM3088JR
0°C to +70°C
8 Pin SO
ADM3088AN –40°C to +85°C
8 Pin Plastic DIP
ADM3088AR
8 Pin SO
–40°C to +85°C
ADM3082/ADM3085/ADM3088TYPICALPERFORMANCECHARACTERISTICS
AW
AI
TI
NG
D
A
AT
TPC1. No-load Supply Current vs.
Temperature
AW
A
I
IT
NG
T
A
D
A
AW
TPC2. Output Current vs. Receiver Output High Voltage
–8–
AI
N
TI
G
T
DA
A
TPC3. Output Current vs. Receiver Output Low Voltage
REV. PrA 02/02
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 TYPICAL PERFORMANCE CHARACTERISTICS (continued)
AW
AI
N
TI
G
T
DA
A
AW
TPC4. Receiver Output High
Voltage vs. Temperature
AW
AI
TI
NG
D
AW
AI
T
DA
AI
N
TI
G
T
DA
AW
AI
N
TI
G
AI
N
TI
G
A
TPC11. ADM3088 Receiver
Propagation Delay vs. Temperature
A
T
DA
A
TPC9. ADM3088 Driver Propagation
Delay vs. Temperature
AW
–9–
G
A
TPC8. ADM3085 Driver Propagation
Delay vs. Temperature
T
DA
AI
N
TI
T
DA
TPC6. Shutdown Current vs.
Temperature
AW
A
TPC10. ADM3082/5 ReceIver
Propagation Delay vs. Temperature
REV. PrA 02/02
AW
A
AT
TPC7. ADM3082 Driver Propagation
Delay vs. Temperature
G
G
A
TPC5. Receiver Output Low
Voltage vs. Temperature
AW
N
TI
AI
N
TI
T
DA
AI
N
TI
G
T
DA
A
TPC12. Driver Differential Output Voltage vs. Temperature
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
ADM3082/ADM3085/ADM3088 TYPICAL PERFORMANCE CHARACTERISTICS (continued)
AW
A
I
IT
NG
T
DA
A
AW
TPC13. Driver Output Current vs. Differential Output Voltage
AW
AI
TI
NG
D
AI
A
AW
A
AT
TPC16. ADM3082 Driver Propagation
Delay
I
IT
NG
T
A
D
G
A
TPC14. Output Current vs. Driver Output High Voltage
AW
AW
N
TI
T
DA
A
I
IT
NG
T
A
D
NG
A
TPC15. Output Current vs. Driver Output Low Voltage
A
AW
TPC17. ADM3085 Driver Propagation
Delay
AW
AI
N
TI
G
T
DA
A
TPC18. ADM3088 Driver Propagation
Delay
A
TPC19. ADM3082/5 Receiver Propagation Delay
A
I
IT
T
DA
A
I
IT
NG
T
A
D
A
TPC20. ADM3088 Receiver
Propagation Delay
–10–
REV. PrA 02/02
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
PIN FUNCTION DESCRIPTION
Pin Mnemonic
Description
1
RO
Receiver Output. When RE is low and A - B $ (more positive than) –50mV, RO will be high.
When RE is low and A – B # (more negative than) –200mV, RO will be low.
2
RE
Receiver Output Enable. Take RE low to enable RO; RO is high impedance when RE is high.
Take RE high and DE low to enter low-power shutdown mode.
3
DE
Driver Output Enable. Take DE high to enable driver outputs. These outputs are high
impedance when DE is low. Take RE high and DE low to enter low-power shutdown mode.
4
DI
Driver Input. With DE high, a low on DI forces non-inverting output low and inverting output
high. Similarly, a high on DI forces non-inverting output high and inverting output low.
5
GND
Ground
6
A
Non-Inverting Receiver Input and Non-Inverting Driver Output
7
B
Inverting Receiver Input and Inverting Driver Output
8
VCC
Positive Supply 4.75V =V CC =5.25V
DEVICE TRUTH TABLES
RECEIVING
TRANSMITTING
INPUTS
INPUTS
OUTPUTS
OUTPUT
RE
DE
DI
B/Z
A/Y
RE
DE
A-B
RO
X
1
1
0
1
0
X
$ -0.05V
1
X
1
0
1
0
0
X
# -0.2V
0
0
0
X
High-Z
High-Z
0
X
Open/shorted
1
1
0
X
1
1
X
High-Z
1
0
X
Shutdown
Shutdown
X = Don’t care
Shutdown mode, driver and receiver outputs high impedance
REV. PrA 02/02
–11–
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
DETAILED
DESCRIPTION
HIGH INPUT IMPEDANCE
The ADM3082, ADM3085 and ADM3088 are highspeed RS-485/RS-422 transceivers offering enhanced performance over industry-standard devices All devices in the
family contain one driver and one receiver, but there is a
choice of performance options. The devices feature failsafe operation, which means that a logic-high receiver output is guaranteed when the receiver inputs are open-circuit
or short-circuit, or when they are connected to a terminated transmission line with all drivers disabled (see the
section on Fail-Safe Operation).
The input impedance of the devices is 96kV, which is 8
times higher than the standard RS-485 load of 12kV. A
standard driver can driver 32 standard loads, so up to 256
ADM308X receivers, or a combination of ADM308X and
other devices up to 32 unit loads, may be connected to an
RS-422/RS485 bus driven by a single driver.
SLEW RATE CONTROL
If shutdown mode is not used, the fact that DE is activehigh and RE is active-low offers a convenient way of
switching the device between transmit and receive, by tying DE and RE together. This is useful, for example, in
applications using half duplex operation and where several
receiver outputs are connected to a serial bus.
The ADM3082 features a controlled slew-rate driver that
minimize electromagnetic interference (EMI) and reduce
reflections caused by incorrectly terminated cables, allowing error-free data transmission rates up to 115kbps (see
the section on Reduced EMI and Reflections).
SHUTDOWN
MODE
All the devices have a low power shutdown mode that is
enabled by taking RE high and DE low.
The driver slew rate of the ADM3088 is not limited, offering data transmission rates up to 10Mbps.
The device is guaranteed not to enter shutdown mode if
DE and RE are driven in this way. If DE is low and RE is
high for less than 50ns the device will not enter shutdown.
If DE is low and RE is high for greater than 600ns, the
device is guaranteed to enter shutdown.
RECEIVER INPUT FILTERING
FAIL-SAFE OPERATION
The ADM3085 offers a higher limit on driver output
slew-rate, allowing data transmission rates up to 500kbps.
The receivers of all devices incorporate input hysteresis.
In addition, when operating in 115kbps or 500kbps mode,
the receivers of the ADM3082 and ADM3085 incorporate
input filtering. This enhances noise immunity with differential signals that have very slow rise and fall times, but it
does increase propagation delay by 20%.
HALF-/FULL-DUPLEX OPERATION
The ADM3082, ADM3085, and ADM3088 are dedicated
half-duplex devices (driver outputs internally linked to receiver inputs). Figure 29 shows a typical half-duplex connection between two devices.
THREE-STATE BUS CONNECTION
All the devices have a Driver Enable pin (DE) that enables the driver outputs when taken high or puts the driver
outputs into a high-impedance state when taken low. This
allows several driver outputs to be connected to an
RS-422/RS-485 bus.
Similarly, all the devices have a (active-low) Receiver Enable pin (RE). Taking this low enables the receiver, while
taking it high puts the receiver outputs into a high-impedance state. This allows several receiver outputs to be connected to a serial data bus.
RE C E IV E R
O UT P UT (RO )
100n
1
ENHANCED ESD PROTECTION
All Analog Devices parts incorporate protection against
electrostatic discharge (ESD) to protect the devices during handling, assembly and normal operation. In addition,
the ADM308X family has enhanced ESD protection up to
±15kV on the receiver inputs and driver outputs (A, B) to
protect against severe operational conditions such as line
transients, connection and disconnection.
+5V
(V C C )
5
8
D
4
DA T A
IN (D I)
3
DR IV E R
E NA BL E (DE )
2
RE C E IV E R
E NA BL E (R E )
1
RE C E IV E R
O UT P UT (RO )
R
RE C E IV E R
E NA BL E (R E )
2
DR IV E R
E NA BL E (DE )
3
DA T A
IN (D I)
The ADM3082/ADM3085/ADM3088 offer true fail-safe
operation while remaining fully compliant with the
±200mV EIA/TIA-485 standard. A logic-high receiver
output is guaranteed when the receiver inputs are shorted
together or open-circuit, or when they are connected to a
terminated transmission line with all drivers disabled.
This is done by setting the receiver threshold between
-50mV and –200mV. If the differential receiver input voltage (A–B) is greater than or equal to –50mV, RO is logic
high. If A–B is less than or equal to –200mV, RO is logic
low. In the case of a terminated bus with all transmitters
disabled, the receiver’s differential input voltage is pulled
to 0V by ADM308X family, which results in a logic high
with a 50mV minimum noise margin.
6
7
RT
RT
4
7
6
D
5
+5V
(V C C )
R
8
100n
AD M 308 2/5/8
AD M 308 2/5/8
Figure 29. Half-Duplex Configuration for ADM3082, ADM3085 or ADM3088
–12–
REV. PrA 02/02
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
CURRENT LIMIT AND THERMAL SHUTDOWN
The ADM3082/ADM3085/ADM3088 incorporate two
protection mechanisms to guard the drivers against shortcircuits, bus contention or other fault conditions. The first
is a foldback current-limited output stage that protects the
driver against short-circuits over the entire common-mode
voltage range. The second is a thermal shutdown circuit
that puts the driver outputs into a high-impedance state if
the die temperature exceeds a safe limit.
AW
REDUCED EMI AND REFLECTIONS
The ADM3082 and ADM3085 incorporate slew-rating limiting in the drivers. This reduces reflections due to incorrect cable termination and minimizes electromagnetic
interference (EMI).
Figures 9 to 11 show driver output waveforms and Fourier
analyses of 20kHz signals for the three different slew-rate
settings. It can be seen that the harmonic content is greatly
reduced for the ADM3085 and still further for the
ADM3082 (Figures 10 and 9 respectively).
A
I
IT
NG
T
DA
A
Figure 11. ADM3088 Driver Output Waveform and FFT Plot
The length of an unterminated stub that can be driven
with only minor reflections depends on the rise time of
the transmitter. A conservative estimate for this is given
by the following equation:
L (metres) = tR / 49.2
where tR is the transmitter’s rise time in ns (multiply result by 3.28 for answer in feet).
AW
AI
N
TI
G
T
DA
For example, the rise time of the ADM3082 is typically
1320ns, which results in acceptable waveforms with stub
lengths up to 27 metres. This is not the ultimate limit on
unterminated stub length, as a system can still work if the
waveformis allowed to settle before sampling the data.
A
The RS-485/RS-422 standard covers line lengths up to
4000 feet (1219 metres). Driver output and receiver output waveforms for the three slew rate settings, driving a
4000 foot cable, are shown in figures 12 to 14.
Figure 9 ADM3082 Driver Output Waveform and FFT Plot
AW
AI
N
TI
G
DA
TA
AW
NG
A
Figure 12. Driver Input, Driver Output and Receiver Output
Waveforms of ADM3082, Driving 4000ft (1219m) of Cable
at 50kHz
Figure 10. ADM3085 Driver Output Waveform and FFT Plot
REV. PrA 02/02
A
I
IT
T
DA
–13–
PRELIMINARY TECHNICAL DATA
ADM3082/ADM3085/ADM3088
APPLICATIONS
T
AI
AW
I
NG
T
A
D
Figures 15 shows a typical application of the device on a
half--duplex network. The line should be terminated at
both ends to minimize reflections and any stubs off the
main line should be kept as short as possible.
A
120 V
R
RO
RE
DE
A
DI
Figure 13. Driver Input, Driver Output and Receiver Output
Waveforms of ADM3085, Driving 4000ft (1219m) of Cable
at 50kHz
D
R
RO
RE
DE
AI
AW
TI
NG
D
D
R
RO
RE
DE
D
R
RO
RE
DE
B
A
DI
D
120 V
AD M 3082, ADM 3084, AD M 308 5
O R AD M 3089 W IT H H /F = V C C
Figure 15. Typical Half-Duplex Network Application
For line lengths in excess of 1220 metres the line should
be split into smaller sections with intermediate repeaters.
OUTLINE
B
A
DI
Figure 14. Driver Input, Driver Output and Receiver Output
Waveforms of ADM3088, Driving 4000ft (1219m) of Cable
at 200kHz
B
A
DI
A
AT
B
DIMENSIONS
Dimensions shown in inches and (mm).
8-Pin Plastic Dual-In-Line Package (N-8)
8-Pin SO Package (R-8)
0.43 0 (10 .92 )
0.19 6 8 (5 . 00)
0.34 8 (8.84 )
8
0.18 9 0 (4 . 80)
5
0. 280 (7.11 )
85
0. 240 (6.10 )
14
0. 325 (8.25 )
P IN 1
0. 060 (1.52 )
0. 015 (0.38 )
0.21 0 (5.33 )
MAX
0.16 0 (4.06 )
0.11 5 (2.93 )
0.02 2 (0.5 58 ) 0.1 0 0 0.07 0 (1.77 )
0.01 4 (0.3 56 ) (2 .54 ) 0.04 5 (1.15 )
BSC
0.1 3 0
(3 .30 )
M IN
S E A T IN G
PLANE
0.15 7 4 (4 .00 )
0. 244 0 (6. 20 )
0. 228 4 (5. 80 )
0. 300 (7.62 )
1
4
0.14 9 7 (3 .80 )
0.19 5 (4. 95)
0.11 5 (2. 93)
P IN 1
0. 015 (0.3 81 )
0. 102 (2.59)
0.01 9 6 (0 . 50)
0. 094 (2.39)
0.00 9 9 (0 . 25)
x 45
0.009 8 (0. 25 )
0. 008 (0.2 04 )
0.004 0 (0. 10 )
SE A TIN G
PLANE
–14–
0.0 5 00
(1 .27 )
BS C
0.01 9 2 (0 . 49)
0.01 3 8 (0 . 35)
0.00 9 8 (0 . 25)
0.00 7 5 (0 . 19)
8
0
0.05 0 0 (1 .27 )
0.01 6 0 (0 .41 )
REV. PrA 02/02
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