High Input Impedance — Up to 256 Transceivers on Bus
GENERAL DESCRIPTION
ADM1487
The ADM1487 is an ultra-low power RS-485/RS-422
transceiver consisting of one driver and one receiver per
package. Quiescent operating current is typically 80µA
and 1µA in shutdown mode. The driver and receiver both
have three-state outputs. This allows multiple drivers to be
connected to an RS-485/RS-422 bus, or several receiver
outputs to be connected to a serial data bus. The driver
will maintain a high-impedance output state even with
power off, while the receiver features fail-safe operation
that guarantees a logic high output if the inputs are left
open-circuit.
The device has slew-rate limited drivers to minimize elec-
tromagnetic interference (EMI) and reduce reflections
caused by incorrectly terminated cables.
±10kV ESD Protection (Human Body Model) on
RS-485 I/O pins
Thermal Protection of Driver
Glitch-Free Driver Power-Up Allows Hot Connection
Driver Maintains High Output Impedance with Power
Off
Wide Common-Mode Range Allows ±7V Ground Differ-
ences Between Devices
Pin-Compatible with Industry Standard 75176
APPLICATIONS
Battery-Powered RS-485/RS-422 Systems
Level Translation
FUNCTIONAL BLOCK DIAGRAM
RO
RE
DE
DI
1
R
8
7
6
D
V
CC
B
A
GND
2
3
4
5
ADM1487
REV. PrC 08/02
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 Box 9106, Norwood, MA 02062-9106, U.S.A.
.O.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 2002
–1–
PRELIMINARY TECHNICAL DATA
ADM1487
ADM1487 SPECIFICATIONS
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +5V ±5%, T
A
= 0°C TO +70°C, UNLESS OTHERWISE NOTED)
Parameter
Differential Driver Output Voltage,V
OD1
Differential Driver Output Voltage, V
OD2
Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States,
Driver Common-Mode Output
Voltage, V
OC
Change in Magnitude of Driver
Common-Mode Output Voltage for
Complementary Output States, |V
OC
|
Input High Voltage (DE, DI,
RE),
V
IH
Input Low Voltage (DE, DI,
RE),
V
IL
Input Current (DE, DI,
RE),
I
IN1
Input Current (A, B), I
IN2
Differential Input Threshold Voltage
for Receiver, V
TH
Receiver Input Hysteresis,
V
TH
Min
Typ
Max
5
Units
V
V
V
V
Test Conditions/Comments
Unloaded, I
O
= 0
Figure 1, R = 50
Figure 1, R = 27
Figure 1, R = 27
(RS-422)
(RS-485)
or R = 50
2.0
1.5
5
0.2
VOD
3
0.2
V
V
Figure 1, R = 27
R = 27
or R = 50
or R = 50
2
0.8
±2
0.30
-0.15
-0.2
45
3.5
0.4
±1
70
96
120
80
1
35
35
7
250
85
200
120
10
250
0.2
V
V
µA
mA
mA
V
mV
V
V
µA
k
µA
µA
µA
mA
mA
mA
DE = 0, V
CC
= 0V or 5.25V, V
IN
= 12V
DE = 0, V
CC
= 0V or 5.25V, V
IN
= –7V
–7V
V
CM
12V
V
CM
= 0V
I
O
=-4mA, V
ID
= 200mV
I
O
= 4mA, V
ID
= –200mV
V
CC
= Max, 0.4V
–7V
V
CM
12V
Vo
2.4V
Receiver Output High Voltage, V
OH
Receiver Output Low Voltage, V
OL
Three-State (High Impedance) Output
Current at Receive, I
OZR
Receiver Input Resistance, R
IN
Supply Current, I
CC
Supply Current in Shutdown Mode, I
SHDN
Driver Short-Circuit Ourrent, I
OSD1
Driver Short-Circuit Ourrent, I
OSD2
Receiver Short-Circuit Current, I
OSR
No Load, Output Enabled
No Load, Output Disabled
DE = 0V,
RE
= V
CC
V
OUT
= HIGH, –7V
V
OUT
= LOW, –7V
0V
V
O
V
OC
V
O
Vo
12V
12V
–2–
Rev. PrC
ADM1487
ADM1487 SPECIFICATIONS (continued)
ELECTRICAL CHARACTERISTICS
(VCC = +5V ±5%, TA = -40°C TO +85°C, UNLESS OTHERWISE NOTED)
Parameter
Differential Driver Output Voltage, V
OD1
Differential Driver Output Voltage, V
OD2
Driver Common-Mode
Output Voltage, V
OC
Differential Input Threshold
Voltage for Receiver, V
TH
Receiver Input Hysteresis,
Supply Current, I
CC
Supply Current in Shutdown Mode, I
SHDN
Driver Input to Output High, t
DPLH
Driver Input to Output Low, t
DPHL
Driver Output to Output, t
SKEW
Driver Rise or Fall Time, t
DR
, t
DF
Receiver Input to Output High, t
RPLH
Receiver Input to Output Low, t
RHL
Differential Receiver Skew, t
SKD
|t
RPLH
-t
RPHL
|
Maximum Data Rate, f
MAX
V
TH
Min
Typ
Max
5
Units Test Conditions/Comments
V
V
V
V
V
mV
Unloaded, I
O
= 0
Figure 1, R = 50
Figure 1, R = 27
Figure 1, R = 27
–7V
V
CM
12V
(RS-422)
(RS-485)
or R = 50
2.0
1.5
5
3
–0.2
45
120
80
1
150
150
100
150
30
30
140
140
13
250
0.2
V
CM
= 0V
No Load, Output Enabled
No Load, Output Disabled
DE = 0V,
RE
= V
CC
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 4, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 4, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 4, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
200
120
10
1200
1200
600
2000
250
250
µA
µA
µA
ns
ns
ns
ns
ns
ns
ns
kbps
SWITCHING CHARACTERISTICS
(V
CC
= +5V ±5%, T
A
= -40°C TO +85°C, UNLESS OTHERWISE NOTED)
Parameter
Driver Input to Output High, t
DPLH
Driver Input to Output, t
DPHL
Driver Output to Output, t
SKEW
Driver Rise or Fall Time, t
DR
, t
DF
Driver Enable to Output High, t
DZH
Driver Enable to Output Low, t
DZL
Driver Disable Time from Low, t
DLZ
Min
150
150
Typ
Max
1200
1200
Units Test Conditions/Comments
ns
ns
ns
ns
ns
ns
ns
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 2, 3, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 5, 6, C
L
= 100pF, S2 Closed
Figures 5, 6, C
L
= 100pF, S1 Closed
Figures 5, 6, C
L
= l5pF, S1 Closed
250
150
100
100
150
600
1200
1500
1500
1500
Rev. PrC
–3–
PRELIMINARY TECHNICAL DATA
ADM1487
ADM1487 SPECIFICATIONS (continued)
SWITCHING CHARACTERISTICS
(V
CC
= +5V ±5%, T
A
= -40°C TO +85°C, UNLESS OTHERWISE NOTED)
Parameter
Driver Disable Time from High, t
DHZ
Receiver Input to Output, t
RPLH
Receiver Input to Output Low, t
RPHL
DifferentialReceiverSkew, t
SKD
|t
PLH
-t
PHL
|
Receiver Enable to Output Low, t
RZL
Receiver Enable to Output High, t
RZH
Receiver Disable from Low, t
RLZ
Receiver Disable from High, t
RHZ
Maximum Data Rate, f
MAX
Time to Shutdown, t
SHDN
Driver Enable from Shutdown to
Output High, t
DZH(SHDN)
Driver Enable from Shutdown to
Output Low, t
DZL(SHDN)
Receiver Enable from Shutdown to
Output High, t
RZH(SHDN)
Receiver Enable from Shutdown to
Output Low, t
RZL(SHDN)
NOTES
1
2
Min
150
30
30
Typ
Max
1500
Units Test Conditions/Comments
ns
ns
ns
ns
Figures 5, 6, C
L
= l5pF, S2 Closed
Figures.2, 4, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures.2, 4, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures.2, 4, R
DIFF
= 54 ,
C
L1
= C
L2
= 100pF
Figures 7, 8, C
RL
= l5pF, S1 Closed
Figures 7, 8, C
RL
= l5pF, S2 Closed
Figures 7, 8, C
RL
= l5pF, S1 Closed
Figures 7, 8, C
RL
= l5pF, S2 Closed
140
140
13
20
20
20
20
250
250
50
50
50
50
ns
ns
ns
ns
kbps
250
50
200
600
2000
2000
2000
2000
ns
ns
ns
ns
ns
DE = 0,
RE
= low to high transition
Figures 5, 6, C
L
= 100pF, S2 Closed
Figures 5, 6, C
L
= 100pF, S1 Closed
Figures 7, 8, C
L
= l5pF, S2 Closed
Figures 7, 8, C
L
= l5pF, S1 Closed
Absolute maximum ratings are those beyond which the safety of the device cannot be guaranfeed.
All currents into device pins are positive; all currents out ot device pins are negative. All voltages are referenced to device ground unless otherwise specified.
3
All typicals are given for Vcc = 5V and Tp = 25°C.
4
The ADM1487 is not tested and is not quality-assurance sampled at -40°C and at 85°C. These specifications are guaranteed by design, correlation, andlor inference from
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