±16.5kV ESD Protected, +125°C, 3.0V to 5.5V, TDFN
Packaged, 16Mbps, Full Fail-safe, Low Power,
RS-485/RS-422 Receiver
ISL3282EMRTEP
The Intersil ISL3282EMRTEP is a ±16.5kV IEC61000 ESD
protected, 3.0V to 5.5V powered, single receiver that meets both
the RS-485 and RS-422 standards for balanced communication.
This receiver has very low bus currents (+125µA/-100µA), so it
presents a true “1/8 unit load” to the RS-485 bus. This allows up to
256 receivers on the network without violating the RS-485
specification’s 32 unit load maximum and without using
repeaters.
Receiver inputs feature a “Full Fail-Safe” design, which ensures a
logic high Rx output if Rx inputs are floating, shorted, or
terminated but undriven.
The ISL3282EMRTEP includes an active low enable pin and is
offered in the Military Temperature range (-55°C to +125°C).
A 26% smaller footprint is available with the TDFN package. This
device also features a logic supply pin (V
L
) that sets the V
OH
level
of the RO output (and the switching points of the RE/RE input) to
be compatible with another supply voltage in mixed voltage
systems.
Features
• Specifications per DSCC VID V62/10601-01XB
• Full Mil-Temp Electrical Performance from -55°C to +125°C
• Controlled Baseline with One Wafer Fabrication Site and One
Assembly/Test Site
• Full Homogeneous Lot Processing in Wafer Fab
• No Combination of Wafer Fabrication Lots in Assembly
• Full Traceability Through Assembly and Test by Date/Trace
Code Assignment
• Enhanced Process Change Notification
• Enhanced Obsolescence Management
• Eliminates Need for Up-Screening a COTS Component
• ±16.5kV IEC61000 ESD Protection on RS-485 Inputs
• Class 3 ESD Level on all Other Pins . . . . . . . . . . . . .>5kV HBM
• Pb-Free (RoHS Compliant)
• Wide Supply Range . . . . . . . . . . . . . . . . . . . . . . . . 3.0V to 5.5V
• Specified for +125°C Operation
• Logic Supply Pin (V
L
) Eases Operation in Mixed Supply Systems
• Full Fail-safe (Open, Short, Terminated/Undriven)
• True 1/8 Unit Load Allows up to 256 Devices on the Bus
• High Data Rates . . . . . . . . . . . . . . . . . . . . . . . . . up to 16Mbps
• Low Quiescent Supply Current . . . . . . . . . . . . . . 500µA (Max)
• Very Low Shutdown Supply Current . . . . . . . . . . . 20µA (Max)
• -7V to +12V Common Mode Input Voltage Range
• Tri-statable Rx Available (Active Low or High EN Input)
• 5V Tolerant Logic Inputs When V
CC
≤
5V
Device Information
The specifications for an Enhanced Product (EP) device are
defined in a Vendor Item Drawing (VID), which is controlled by the
Defense Supply Center in Columbus (DSCC). “Hot-links” to the
applicable VID and other supporting application information are
provided on our website.
Applications
• Clock Distribution
• High Node Count Systems
• Space Constrained Systems
• Security Camera Networks
• Building Environmental Control/Lighting Systems
• Industrial/Process Control Networks
TABLE 1. SUMMARY OF FEATURES
PART NUMBER
ISL3282EMRTEP
FUNCTION
1 Rx
DATA RATE
(Mbps)
16
# DEVICES ON
BUS
256
RX
ENABLE?
ACTIVE LOW
V
L
PIN?
YES
QUIESCENT I
CC
(µA)
350
LOW POWER
SHUTDOWN?
YES
LEAD
COUNT
8-TDFN
February 15, 2011
FN7595.1
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774
|
Copyright Intersil Americas Inc. 2010, 2011. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
ISL3282EMRTEP
Ordering Information
PART NUMBER
(Notes 1, 2)
ISL3282EMRTEP-T
ISL3282EMRTEP-TK
NOTES:
1. These Intersil Pb-free plastic packaged products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin
plate PLUS ANNEAL - e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-
free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
2. Please refer to
TB347
for details on reel specifications.
3. For Moisture Sensitivity Level (MSL), please see device information page for
ISL3282EMRTEP.
For more information on MSL please see techbrief
TB363.
VENDOR ITEM DRAWING
V62/10601-01XB
V62/10601-01XB
282
282
PART MARKING
TEMP. RANGE
(°C)
-55 to +125
-55 to +125
PACKAGE
(Tape and Reel)
(Pb-Free)
8 Ld TDFN
8 Ld TDFN
Truth Table
RECEIVING
INPUTS
RE
0
0
0
1
A-B
≥
-0.05V
≤
-0.2V
Inputs Open/Shorted
X
OUTPUT
RO
1
0
1
High-Z*
Pin Configurations
ISL3282EMRTEP
(8 LD TDFN)
TOP VIEW
RO
GND
NC
V
CC
1
2
3
4
R
8
7
6
5
B
RE
V
L
A
Pin Descriptions
PIN NAME
RO
RE
GND
A
B
V
CC
V
L
NC
FUNCTION
Receiver output: If A - B
≥
-50mV, RO is high; If A - B
≤
-200mV, RO is low; RO = High if A and B are unconnected (floating) or shorted.
Receiver output enable. RO is enabled when RE is low; RO is high impedance when RE is high. If the Rx enable function isn’t used, connect
RE directly to GND. RE is internally pulled high.
Ground connection. This is also the potential of the TDFN thermal pad.
±16.5kV
IEC61000 ESD Protected RS-485, RS-422 level, noninverting receiver input.
±16.5kV
IEC61000 ESD Protected RS-485, RS-422 level, inverting receiver input.
System power supply input (3.0V to 5.5V). On devices with a V
L
pin, power-up V
CC
first.
Logic-Level Supply which sets the V
IL
/V
IH
levels for the RE pin, and sets the V
OH
level of the RO output. Power-up this supply after V
CC
, and
keep V
L
≤
V
CC.
No Connection.
2
FN7595.1
February 15, 2011
ISL3282EMRTEP
Typical Operating Circuits
NETWORK WITH V
L
PIN FOR INTERFACE TO LOWER VOLTAGE LOGIC DEVICES
1.8V
6
V
CC
V
L
+3.3V TO 5V
+
4
V
CC
R
T
0.1µF
0.1µF
+
8
V
CC
1
V
L
V
CC
+3.3V
2.5V
ISL3282EMRTEP
LOGIC
DEVICE
(µP, ASIC,
UART)
ISL3298EMRTEP
5
8
6
7
Y
Z
D
DI 3
DE 2
LOGIC
DEVICE
(mP, ASIC,
UART)
1 RO
7 RE
A
R
B
GND
2
GND
4, 5
Test Circuits and Waveforms
V
CC
GND
B
A
R
RE
RE
RO
15pF
B
0V
A
t
PLH
SIGNAL
GENERATORS
RO
50%
t
PHL
V
CC
OR V
L
50%
0V
0V
-1V
+1V
FIGURE 1A. TEST CIRCUIT
FIGURE 1B. MEASUREMENT POINTS
FIGURE 1. RECEIVER PROPAGATION DELAY AND DATA RATE
RE
GND
SIGNAL
GENERATOR
B
A
R
RO
1kΩ
V
CC
OR V
L
SW
15pF
RO
GND
t
ZH
OUTPUT HIGH
50%
t
HZ
RE
1.5V
1.5V
3V
0V
V
OH
- 0.25V
V
OH
0V
PARAMETER
t
HZ
t
LZ
t
ZH
t
ZL
A
+1.5V
-1.5V
+1.5V
-1.5V
SW
GND
V
CC
OR V
L
GND
V
CC
OR V
L
RO
t
ZL
50%
OUTPUT LOW
t
LZ
V
CC
OR V
L
V
OL
+ 0.25V V
OL
FIGURE 2A. TEST CIRCUIT
FIGURE 2B. MEASUREMENT POINTS
FIGURE 2. RECEIVER ENABLE AND DISABLE TIMES
3
FN7595.1
February 15, 2011
ISL3282EMRTEP
Application Information
RS-485 and RS-422 are differential (balanced) data transmission
standards for use in long haul or noisy environments. RS-422 is a
subset of RS-485, so RS-485 transceivers are also RS-422
compliant. RS-422 is a point-to-multipoint (multidrop) standard,
which allows only one driver and up to 10 (assuming one unit load
devices) receivers on each bus. RS-485 is a true multipoint
standard, which allows up to 32 one unit load devices (any
combination of drivers and receivers) on each bus.
Another important advantage of RS-485 is the extended
common mode range (CMR), which specifies that the driver
outputs and receiver inputs withstand signals that range from
+12V to -7V. RS-422 and RS-485 are intended for runs as long as
4000’, so the wide CMR is necessary to handle ground potential
differences, as well as voltages induced in the cable by external
fields.
GND
V
CC
= +3.3V TO 5V
V
CC
= +2V
V
L
RO
V
OH
= 2V
R
XD
ESD
DIODE
RE
V
IH
= 1V
V
OH
≤
2V
RXEN
GND
ISL3282E
UART/PROCESSOR
FIGURE 3. USING V
L
PIN TO ADJUST LOGIC LEVELS
Wide Supply Range
The ISL3282EMRTEP is designed to operate with a wide range
of supply voltages from 3.0V to 5.5V. This device meets the
RS-422 and RS-485 specifications over this full range.
Receiver Features
This device utilize a differential input receiver for maximum noise
immunity and common mode rejection. Input sensitivity is better
than ±200mV, as required by the RS-422 and RS-485
specifications.
Receiver input resistance of 96kΩ surpasses the RS-422
specification of 4kΩ and is eight times the RS-485 “Unit Load
(UL)” requirement of 12kΩ minimum. Thus, these products are
known as “one-eighth UL” transceivers and there can be up to
256 of these devices on a network while still complying with the
RS-485 loading specification.
Receiver inputs function with common mode voltages as great as
+9V/-7V outside the power supplies (i.e., +12V and -7V), making
them ideal for long networks where induced voltages, and ground
potential differences are realistic concerns.
The ISL3282EMRTEP includes a “full fail-safe” function that
guarantees a high level receiver output if the receiver inputs are
unconnected (floating), shorted together, or connected to a
terminated but undriven bus. Fail-safe with shorted inputs is
achieved by setting the Rx upper switching point to -50mV, thereby
ensuring that the Rx sees 0V differential as a high input level.
The receiver can easily support a 16Mbps data rate, and its
output is tri-statable via the active low RE input.
TABLE 2. V
IH
, V
IL
AND DATA RATE vs V
L
FOR V
CC
= 3.3V OR 5V
V
L
(V)
1.35
1.6
1.8
2.3
2.7
3.3
5.5 (i.e., V
CC
)
V
IH
(V)
0.55
0.7
0.8
1
1.1
1.3
2
V
IL
(V)
0.5
0.6
0.7
0.9
1
1.2
1.8
DATA RATE
(Mbps)
11
16
23
27
30
30
24
Logic Supply (V
L
Pin)
Note: Power-up V
CC
before powering up the V
L
supply.
The ISL3282EMRTEP includes a V
L
pin that powers the logic
input (RE) and/or the Rx output. These pins interface with “logic”
devices such as UARTs, ASICs, and microcontrollers. Today, most
of these devices use power supplies significantly lower than 3.3V,
thus, a 3.3V output level from a 3.3V powered RS-485 IC might
seriously overdrive and damage the logic device input. Similarly,
the logic device’s low V
OH
might not exceed the V
IH
of a 3.3V or
5V powered RE input. Connecting the V
L
pin to the power supply
of the logic device (as shown in Figure 3) limits the
ISL3282EMRTEP’s Rx output V
OH
to V
L
(see Figures 6 through
10), and reduces the RE input switching point to a value
compatible with the logic device’s output levels. Tailoring the
logic pin input switching point and output levels to the supply
voltage of the UART, ASIC, or microcontroller eliminates the need
for a level shifter/translator between the two ICs.
V
L
can be anywhere from V
CC
down to 1.35V, but the input
switching points may not provide enough noise margin when
V
L
< 1.6V. Table 2 indicates typical V
IH
, V
IL
, and data rate values
for various V
L
settings so the user can ascertain whether or not a
particular V
L
voltage meets his/her needs.
The quiescent, RO unloaded, V
L
supply current (I
L
) is typically less
than 60µA for V
L
≤
3.3V, as shown in Figure 5.
ESD Protection
All pins on the device include class 3 (>4kV) Human Body
Model (HBM) ESD protection structures, but the RS-485 pins
(receiver inputs) incorporate advanced structures allowing them
to survive ESD events in excess of ±16.5kV HBM and ±16.5kV
IEC61000. The RS-485 pins are particularly vulnerable to ESD
damage because they typically connect to an exposed port on
the exterior of the finished product. Simply touching the port
pins, or connecting a cable, can cause an ESD event that might
destroy unprotected ICs. These new ESD structures protect the
device whether or not it is powered up, and without degrading
the RS-485 common mode range of -7V to +12V. This built-in
4
FN7595.1
February 15, 2011
ISL3282EMRTEP
ESD protection eliminates the need for board level protection
structures (e.g., transient suppression diodes), and the
associated, undesirable capacitive load they present.
Data Rate, Cables, and Terminations
RS-485, RS-422 are intended for network lengths up to 4000’,
but the maximum system data rate decreases as the
transmission length increases. Networks operating at 16Mbps
are limited to lengths less than 100’, while a 250kbps network
that uses slew rate limited transmitters can operate at that data
rate over lengths of several thousand feet.
Twisted pair is the cable of choice for RS-485, RS-422 networks.
Twisted pair cables tend to pick up noise and other
electromagnetically induced voltages as common mode signals,
which are effectively rejected by the differential receiver in these ICs.
To minimize reflections, proper termination is imperative for high
data rate networks. Short networks using slew rate limited
transmitters need not be terminated, but terminations are
recommended unless power dissipation is an overriding concern.
In point-to-point, or point-to-multipoint (single driver on bus)
networks, the main cable should be terminated in its
characteristic impedance (typically 120Ω) at the end farthest
from the driver. In multi-receiver applications, stubs connecting
receivers to the main cable should be kept as short as possible.
Multipoint (multi-driver) systems require that the main cable be
terminated in its characteristic impedance at both ends. Stubs
connecting a transmitter or receiver to the main cable should be
kept as short as possible.
IEC61000-4-2 Testing
The IEC61000 test method applies to finished equipment, rather
than to an individual IC. Therefore, the pins most likely to suffer
an ESD event are those that are exposed to the outside world (the
RS-485 pins in this case), and the IC is tested in its typical
application configuration (power applied) rather than testing
each pin-to-pin combination. The lower current limiting resistor
coupled with the larger charge storage capacitor yields a test
that is much more severe than the HBM test. The extra ESD
protection built into this device’s RS-485 pins allows the design
of equipment meeting level 4 criteria without the need for
additional board level protection on the RS-485 port.
AIR-GAP DISCHARGE TEST METHOD
For this test method, a charged probe tip moves toward the IC pin
until the voltage arcs to it. The current waveform delivered to the
IC pin depends on approach speed, humidity, temperature, etc.,
so it is difficult to obtain repeatable results. The A and B RS-485
pins withstand ±16.5kV air-gap discharges.
CONTACT DISCHARGE TEST METHOD
During the contact discharge test, the probe contacts the tested
pin before the probe tip is energized, thereby eliminating the
variables associated with the air-gap discharge. The result is a
more repeatable and predictable test, but equipment limits
prevent testing devices at voltages higher than ±9kV. The
ISL3282EMRTEP can survive ±9kV contact discharges on the RS-
485 pins.
Low Power Shutdown Mode
This BiCMOS receiver uses a fraction of the power required by its
bipolar counterparts, and include a shutdown feature that
reduces the already low quiescent I
CC
to a 20µA trickle. They
enter shutdown whenever the receiver is disabled (RE = V
CC
).
5
FN7595.1
February 15, 2011
京公网安备 11010802033920号
EEWORLD
