1
FN6051.7
ISL8487E, ISL81487L, ISL81487E
±15kV ESD Protected, 1/8 Unit Load, 5V,
Low Power, High Speed or Slew Rate
Limited, RS-485/RS-422 Transceivers
These Intersil RS-485/RS-422 devices are ESD protected,
fractional unit load (UL), BiCMOS, 5V powered, single
transceivers that meet both the RS-485 and RS-422
standards for balanced communication. Each driver output/
receiver input is protected against ±15kV ESD strikes,
without latch-up. Unlike competitive devices, this Intersil
family is specified for 10% tolerance supplies (4.5V to 5.5V).
All devices present a 1/8 “unit load” to the RS-485 bus,
which allows up to 256 transceivers on the network for large
node count systems (e.g., process automation, remote
meter reading systems). In a remote utility meter reading
system, individual (apartments for example) utility meter
readings are routed to a concentrator via an RS-485
network, so the high allowed node count minimizes the
number of repeaters required to network all the meters. Data
for all meters is then read out from the concentrator via a
single access port, or a wireless link.
Slew rate limited drivers on the ISL8487E and ISL81487L
reduce EMI, and minimize reflections from improperly
terminated transmission lines, or unterminated stubs in
multidrop and multipoint applications. Data rates up to
250kbps are achievable with these devices.
Data rates up to 5Mbps are achievable by using the
ISL81487E, which features higher slew rates.
Receiver (Rx) inputs feature a “fail-safe if open” design,
which ensures a logic high Rx output if Rx inputs are floating.
Driver (Tx) outputs are short circuit protected, even for
voltages exceeding the power supply voltage. Additionally,
on-chip thermal shutdown circuitry disables the Tx outputs to
prevent damage if power dissipation becomes excessive.
These half duplex devices multiplex the Rx inputs and Tx
outputs to allow transceivers with Rx and Tx disable
functions in 8 lead packages.
Features
RS-485 I/O Pin ESD Protection . . . . . . . . . . ±15kV HBM
- Class 3 ESD Level on all Other Pins . . . . . . >7kV HBM
Fractional Unit Load Allows up to 256 Devices on the Bus
Specified for 10% Tolerance Supplies
High Data Rate Version (ISL81487E) . . . . . up to 5Mbps
Slew Rate Limited Versions for Error Free Data
Transmission (ISL8487E, ISL81487L) . . . . .up to 250kbps
Low Current Shutdown Mode (Except ISL81487E). . . 0.5A
Low Quiescent Supply Current:
- ISL8487E, ISL81487L . . . . . . . . . . . . . . . 145A (Max.)
- ISL81487E . . . . . . . . . . . . . . . . . . . . . . . . 420A (Max.)
-7V to +12V Common Mode Input Voltage Range
Three State Rx and Tx Outputs
30ns Propagation Delays, 5ns Skew (ISL81487E)
Half Duplex Pinouts
Operate from a Single +5V Supply (10% Tolerance)
Current Limiting and Thermal Shutdown for Driver
Overload Protection
Pin Compatible Replacements for: MAX487E, (ISL8487E);
LTC1487, ADM1487 (ISL81487L); MAX1487E, ST485ER
(ISL81487E)
Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
High Node Count Networks
Automated Utility Meter Reading Systems
Factory Automation
Security Networks
Building Environmental Control Systems
Industrial/Process Control Networks
TABLE 1. SUMMARY OF FEATURES
PART
NUMBER
HALF/FULL
DUPLEX
NO. OF DEVICES
ALLOWED ON BUS
DATA RATE
(Mbps)
SLEW-RATE
LIMITED?
RECEIVER/
DRIVER ENABLE?
QUIESCENT
ICC (A)
LOW POWER
SHUTDOWN?
PIN
COUNT
ISL8487E
Half
256
0.25
Yes
120
Yes
8
ISL81487L
Half
256
0.25
Yes
120
Yes
8
ISL81487E
Half
256
5
No
Yes
350
No
8
Data Sheet
February 27, 2006
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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