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PDF ( 数据手册 , 数据表 ) ADM1487

零件编号 ADM1487
描述 Ultralow Power RS-485/RS-422 Transceiver
制造商 Analog Devices
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ADM1487 数据手册, 描述, 功能
PRELIMINARY TECHNICAL DATA
a
Ultra-Low Power RS-485/RS-422 Transceiver
with Low EMI and +/-10kV ESD Protection
Preliminary Technical Data
ADM1487
FEATURES
Low Power - 120µA Max ICC with Driver Disabled
High Input Impedance — Up to 256 Transceivers on Bus
Low-Current (1µA) Shutdown Mode
Slew Rate Control for Error-Free Data
Transmission and Low EMI
±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
GENERAL DESCRIPTION
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.
FUNCTIONAL BLOCK DIAGRAM
RO 1
w RE 2
w DE 3
w DI 4
R
D
8 VCC
7B
6A
5 GND
.D ADM1487
ataSheetREV. PrC 08/02
4Information furnished by Analog Devices is believed to be accurate and
Ureliable. 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
comotherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 2002
–1–







ADM1487 pdf, 数据表
ADM1487
PRELIMINARY TECHNICAL DATA
CMOS outout stages, which include parasitic diodes from
their driver outputs to each supply rail and can latch up
when these diodes conduct.
VCC
SCHOTTKY
R E V E R S E -B IA S E D
WHEN OUTPUT
> VCC+VD
PARASITIC
DIODE DP
PARASITIC
DIODE DP
SCHOTTKY
R E V E R S E -B IA S E D
WHEN OUTPUT
< GND - VD
Figure 9. ADM1487 Driver Output Stage
The ADM1487 output includes Schottky diodes in series
with the positive supply to the drain of the P-channel output
device and in series with the drain of the N-channel output
device. These diodes prevent the P-channel's parasitic diode
from conducting when the output voltage exceeds VCC and
prevent the N-channel's parasitic diode from conducting
when the output voltage falls below ground.
SLEW RATE CONTROL
The driver output stage of the ADM1487 has a controlled
slew rate to minmize signal reflections on incorrectly termi-
nated lines and to reduce electromagnetic interference (EMI).
CURRENT LIMIT AND THERMAL SHUTDOWN
The ADM1487 incorporates two protection mechanisms to
guard the drivers against short-circuits, bus contention or
other fault conditions. The first is a current-limited output
stage that protects the driver against short-circuits over the
entire common-mode voltage range by limiting the output
current to about 70mA. Under extreme fault condtions
where the current limit is not effective, a thermal shutdown
circuit puts the driver outputs into a high-impedance state if
the die temperature exceeds 150°C, and does not turn them
back on until the temperature has fallen to 130°C.
ENHANCED ESD PROTECTION
All Analog Devices parts incorporate protection against
electrostatic discharge (ESD) to protect the devices dur-
ing handling, assembly and normal operation. In addition,
the ADM1487 has enhanced ESD protection up to ±10kV
on the A and B I/O pins to protect against severe opera-
tional conditions such as line transients, connection and
disconnection.
APPLICATION INFORMATION
Figure 10 shows a typical application of the ADM1487.
This is a half-duplex RS-485/RS-422 network. Up to 254
additional ADM1487s can be connected along the cable
(termination resistors are only required at each end).
+5V
RECEIVER
OUTPUT
(RO)
RECEIVER
ENABLE
DRI(VREER)
1
2
3
R
8
7B
RT
6
100n (VCC
)
CABLE TERMINATED
AT ENDS
5
6
RT
7
D 4 DI
3 DE
2 RE
ENABLE
DA(DTEA)
IN (DI)
4
D
A
5
BABA
+5V (VCC) 8
100n
R
1 RO
ADM1487
ADDITIONAL
ADM1487s
ADM1487
Figure 10. Typical Half-Duplex RS-485/RS-422 Network
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Pin Plastic Dual-In-Line Package (N-8)
8-Pin SO Package (R-8)
0.430 (10.92)
0.348 (8.84)
85
0.280 (7.11)
0.240 (6.10)
14 0.325 (8.25)
PIN 1
0.060 (1.52)
0.300 (7.62)
0.210 (5.33)
0.015 (0.38)
MAX
0.130
0.160 (4.06)
0.115 (2.93)
(3.30)
MIN
0.022 (0.558) 0.100 0.070 (1.77)
0.014 (0.356) (2.54) 0.045 (1.15)
BSC
SE A TIN G
PLANE
0.195 (4.95)
0.115 (2.93)
0.015 (0.381)
0.008 (0.204)
0.1968 (5.00)
0.1890 (4.80)
0.244 0 (6.20)
0.228 4 (5.80)
85
1
0.1574 (4.00)
4 0.1497 (3.80)
PIN 1
0.102 (2.59)
0.094 (2.39)
0.0196 (0.50)
x 45
0.0099 (0.25)
0.009 8 (0 .25)
0.004 0 (0 .10)
SE A TIN G
PLANE
0.0500
(1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
0.0098 (0.25)
0.0075 (0.19)
8
0
0.05 00 (1 .27)
0.01 60 (0 .41)
–8– Rev. PrC














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