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ADM1487 데이터시트 PDF




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부품번호 ADM1487 기능
기능 Ultralow Power RS-485/RS-422 Transceiver
제조업체 Analog Devices
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ADM1487 데이터시트, 핀배열, 회로
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, 반도체, 판매, 대치품
PRELIMINARY TECHNICAL DATA
ADM1487
ADM1487SPECIFICATIONS(continued)
SWITCHING CHARACTERISTICS (VCC = +5V ±5%, TA = -40°C TO +85°C, UNLESS OTHERWISE NOTED)
Parameter
Min Typ Max Units Test Conditions/Comments
Driver Disable Time from High, tDHZ
Receiver Input to Output, tRPLH
Receiver Input to Output Low, tRPHL
DifferentialReceiverSkew, tSKD
|tPLH-tPHL|
Receiver Enable to Output Low, tRZL
Receiver Enable to Output High, tRZH
Receiver Disable from Low, tRLZ
Receiver Disable from High, tRHZ
Maximum Data Rate, fMAX
Time to Shutdown, tSHDN
Driver Enable from Shutdown to
Output High, tDZH(SHDN)
Driver Enable from Shutdown to
Output Low, tDZL(SHDN)
Receiver Enable from Shutdown to
Output High, tRZH(SHDN)
Receiver Enable from Shutdown to
Output Low, tRZL(SHDN)
150
30
30
250
50
1500
ns Figures 5, 6, CL= l5pF, S2 Closed
140 250 ns Figures.2, 4, RDIFF= 54,
CL1 = CL2 = 100pF
140 250 ns Figures.2, 4, RDIFF= 54,
CL1 = CL2 = 100pF
13 ns Figures.2, 4, RDIFF= 54,
CL1 = CL2 = 100pF
20 50 ns Figures 7, 8, CRL = l5pF, S1 Closed
20 50 ns Figures 7, 8, CRL = l5pF, S2 Closed
20 50 ns Figures 7, 8, CRL = l5pF, S1 Closed
20 50 ns Figures 7, 8, CRL = l5pF, S2 Closed
kbps
200 600 ns DE = 0, RE = low to high transition
2000
ns Figures 5, 6, CL = 100pF, S2 Closed
2000
ns Figures 5, 6, CL = 100pF, S1 Closed
2000
ns Figures 7, 8, CL = l5pF, S2 Closed
2000
ns Figures 7, 8, CL = l5pF, S1 Closed
NOTES
1Absolute maximum ratings are those beyond which the safety of the device cannot be guaranfeed.
2All currents into device pins are positive; all currents out ot device pins are negative. All voltages are referenced to device ground unless otherwise specified.
3All typicals are given for Vcc = 5V and Tp = 25°C.
4The 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
0°C, 25°C and/or 70°C tests.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (Vcc) . . . . . . . . . . . . . . . . . . . . . . . . . . 12V
Control Input Voltage . . . . . . . . . . . –0.5V to Vcc + 0.5V
Driver Input Voltage . . . . . . . . . . . –0.5V to Vcc + 0.5V
Driver Output Voltage . . . . . . . . . . . . . . . . . . . . . . . . ±14V
Receiver InputVoltage . . . . . . . . . . . . . . . . . . . . . . . . ±14V
Receiver Output Voltage . . . . . . . . . –0.5V to Vcc + 0.5V
Operating Temperature Range . . . . . . 0°C Յ TA Յ 70°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . 300°C
*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
PIN CONFIGURATION
RO 1
8 VCC
RE 2 ADM1487 7 B
TOP VIEW
DE 3 (Not to Scale) 6 A
DI 4
5 GND
ORDERING INFORMATION
Model
Temperature Range Package Option
ADM1487JN 0°C to +70°C
8 Pin Plastic DIP
ADM1487JR 0°C to +70°C
8 Pin SO
ADM1487AN –40°C to +85°C
8 Pin Plastic DIP
ADM1487AR –40°C to +85°C
8 Pin SO
–4– Rev. PrC

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ADM1487 전자부품, 판매, 대치품
PRELIMINARY TECHNICAL DATA
ADM1487
TRANSMITTING
INPUTS
RE D E
X1
X1
00
10
DI
1
0
X
X
DEVICE TRUTH TABLES
OUTPUTS
ZY
RECEIVING
RE
01
0
10
0
High-Z
High-Z
0
Shutdown*
1
INPUTS
DE
X
X
X
0
OUTPUT
A-B R O
Ն 0.2V
1
Յ -0.2V
0
Open/shorted
1
X Shutdown*
X = Don’t care
CIRCUIT DESCRIPTION
The ADM1487 is a differential input, differential output
transceiver designed RS-485/RS-422 serial data communi-
cations over twisted-pair cables. It is a half-duplex device
intended for alternate transmission and reception of data
over a single twisted-pair cable, and the driver outputs and
receiver inputs are internally linked and brought out to a
single pair of pins.
Its principal features include ultra-low power operation, a
controlled slew-rate driver that minimizes electromagnetic
interference (EMI) and signals reflections due to incor-
rectly terminated lines, and high input impedance that al-
lows up to 256 receivers to be connected to a bus.
THREE-STATE BUS CONNECTION
The ADM1487 has a Driver Enable pin (DE) that enables
the driver outputs when taken high or puts the driver out-
puts into a high-impedance state when taken low. This al-
lows several driver outputs to be connected to an RS-422/
RS-485 bus.
Similarly, the device has a (active-low) Receiver Enable
pin (RE). Taking this low enables the receiver, while tak-
ing it high puts the receiver outputs into a high-impedance
state. This allows several receiver outputs to be connected
to a serial data bus.
The input impedance of the device is 96k, which is 8
times higher than the standard RS-485 load of 12k. A
standard driver can driver 32 standard loads, so up to 256
ADM1487 receivers, or a combination of ADM1487 and
other devices up to 32 unit loads, may be connected to an
RS-422/RS485 bus driven by a single driver.
LOW POWER OPERATION
The ADM1487 draws very little supply current (typically
80µA) when the driver outputs are disabled or unloaded.
This will increase by up to 72µA if the driver outputs are
enabled (but unloaded) and applying the maximum output
swing of 5V across the receiver input resistors.
However, in practical applications with the device driving
and RS-485/RS422 cable or bus, the current drain is
dominated by the current sourced into the line termination
resistors and any other devices on the bus. With a half-ter-
mination (120load) between the driver outputs, the load
current can be in excess of 13mA as the drivers force a
minimum of 1.5V across the line, and can be greater than
25mA with a fully terminated 60line attached.
*In shutdown mode, driver and receiver outputs high impedance
SHUTDOWN MODE
If RE is taken high while DE is taken low, the device will
enter a low-power shutdown mode, in which the supply
current is typically 1µA.
If the driver outputs are active immediately before shut-
down (DE high), the supply current will not drop to 1µ
until the driver outputs have settled to their three-state
mode, which can take up to 2.6µs worst-case. If DE is al-
ready low and shutdown is entered by taking RE high, the
supply current will drop to 1µA very quickly.
When RE is taken low and/or DE is takem high, the de-
vice will wake up within 3.5µs.
If shutdown mode is not used, the fact that DE is active-
high and RE is active-low offers a convenient way of
switching the device between transmit and receive, by ty-
ing 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 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 INPUTS
The ADM1487 receiver has an input common-mode
range covering the entire RS-485 range of –7V to 12V.
Internal 96kinput resistors from each line terminal to
ground provide a 1/8 unit load to the RS485 bus.
Differential signals greater than ±200mV within the speci-
fied input common-mode range are converted to a TTL-
compatible logic signal at the receiver output. A small
amount of input hysteresis is included to minimize the ef-
fects of noise on the line signals. If the line is terminated
or the receiver inputs are shorted together, the receiver
output will retain the last valid line signal due to the
45mV of hysteresis incorporated in the receiver circuit. If
the receiver inputs are left floating (unterminated), an in-
ternal pull-up of 10µA at the A input will force the re-
ceiver output to a guranteed high output state.
DRIVER OUTPUT STAGE
The RS-485 specification requires that a transceiver with-
stand common-mode voltages of up to 12V above or –7V
below system ground at the RS-485 line connections.
In addition, the transceiver must be protected against both
ESD and latch-up. This precludes the use of conventional
Rev. PrC
–7–

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