DATASHEET

16kV ESD Protected, +125°C, 3.0V to 5.5V, TDFN
Packaged, Low Power RS-485/RS-422 Transmitter
ISL3298EMRTEP
Features
The Intersil ISL3298EMRTEP is a ±16.5kV HBM ESD Protected
(7kV IEC61000 contact), 3.0V to 5.5V powered, single
transmitter for balanced communication using the RS-485 and
RS-422 standards. This driver has very low bus currents (±40mA),
so it presents less than a “1/8 unit load” to the RS-485 bus. This
allows more than 256 transmitters on the network without
violating the RS-485 specification’s 32 unit load maximum, and
without using repeaters.
• Specifications per DLA VID V62/10602
• 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
• High ESD Protection on RS-485 Outputs . . . . ±16.5kV HBM
- IEC61000-4-2 Contact Test Method. . . . . . . . . . . . . . . ±7kV
- Class 3 ESD Level on all Other Pins. . . . . . . . . . .>8kV HBM
Hot Plug circuitry ensures that the Tx outputs remain in a high
impedance state while the power supply stabilizes.
The driver on the ISL3298EMRTEP is not limited, so it can achieve a
16Mbps data rate and is offered in the -55°C to +125°C
temperature range.
This devices also feature a logic supply pin (VL) that sets the
switching points of the DE and DI inputs to be compatible with a
lower supply voltage in mixed voltage systems.
• Specified for +125°C Operation (VCC ≤ 3.6V Only)
For a companion single RS-485 receiver in micro packages,
please see the ISL3282EMRTEP data sheet.
• Logic Supply Pin (VL) Eases Operation in Mixed Supply Systems
Applications
• Low Tx Leakage Allows >256 Devices on the Bus
• Hot Plug - Tx Output Remains Three-state During Power-up
• High Data Rates . . . . . . . . . . . . . . . . . . . . . . . . . up to 16Mbps
• Clock Distribution
• Low Quiescent Supply Current . . . . . . . . . . . . . . .150µA (Max)
- Very Low Shutdown Supply Current . . . . . . . . . . 1µA (Max)
• High Node Count Systems
• Space Constrained Systems
• -7V to +12V Common Mode Output Voltage Range (VCC ≤ 3.6V
Only)
• Security Camera Networks
• Building Environmental Control/Lighting Systems
• Current Limiting and Thermal Shutdown for Driver Overload
Protection (VCC ≤ 3.6V Only)
• Industrial/Process Control Networks
• Tri-statable Tx Output
• 5V Tolerant Logic Input When VCC ≤5V
TABLE 1. SUMMARY OF FEATURES
PART
NUMBER
ISL3298EMRTEP
July 28, 2011
FN7607.1
FUNCTION
DATA RATE
(Mbps)
SLEW-RATE
LIMITED?
HOT
PLUG?
VL
PIN?
TX
ENABLE?
MAXIMUM
QUIESCENT ICC
(µA)
LOW POWER
SHUTDOWN?
PIN
COUNT
1 Tx
16
NO
YES
YES
YES
150
YES
8-TDFN
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.
ISL3298EMRTEP
Pin Configuration
Truth Table
ISL3298EMRTEP
(8 LD TDFN)
TOP VIEW
TRANSMITTING
INPUTS
OUTPUTS
DE
DI
Z
Y
1
1
0
1
1
0
1
0
0
X
High-Z *
High-Z *
VL
1
DE
2
DI
GND
8
VCC
7
Z
3
6
Y
4
5
GND
D
NOTE: *Shutdown Mode
Pin Descriptions
PIN NUMBER
PIN SYMBOL
FUNCTION
1
VL
Logic-Level supply which sets the VIL/VIH levels for the DI and DE pins. Power-up this supply after VCC, and keep VL
≤ VCC.
2
DE
Driver output enable. The driver outputs, Y and Z, are enabled by bringing DE high, and are high impedance when
DE is low. If the driver enable function isn’t needed, connect DE to VCC (or VL) through a 1kΩ to 3kΩ resistor.
3
DI
Driver input. A low on DI forces output Y low and output Z high. Similarly, a high on DI forces output Y high and output
Z low.
4, 5
GND
6
Y
±15kV HBM, ±7kV IEC61000 (contact method) ESD Protected RS-485/422 level, noninverting transmitter output.
7
Z
±15kV HBM, ±7kV IEC61000 (contact method) ESD Protected RS-485/422 level, inverting transmitter output.
8
VCC
Ground connection. This is also the potential of the TDFN thermal pad.
System power supply input (3.0V to 5.5V). On devices with a VL pin, power-up VCC first.
Ordering Information
PART NUMBER
(Note)
VENDOR ITEM
DRAWING
PART
MARKING
TEMP. RANGE
(°C)
PACKAGE
(Tape and Reel)
ISL3298EMRTEP-T
V62/10602-01XB
298
-55 to +125
8 Ld TDFN
ISL3298EMRTEP-TK
V62/10602-01XB
298
-55 to +125
8 Ld TDFN
NOTE: Please refer to TB347 for details on reel specifications.
2
FN7607.1
July 28, 2011
ISL3298EMRTEP
Typical Operating Circuit
NETWORK WITH VL PIN FOR INTERFACING TO LOWER VOLTAGE LOGIC DEVICES
2.5V
+3.3V TO 5V
+3.3V
+
4
VCC
6
VL
VCC
0.1µF
0.1µF
8
1 RO
R
1
VL
VCC
ISL3282EMRTEP
LOGIC
DEVICE
(µP, ASIC,
UART)
1.8V
+
VCC
ISL3298EMRTEP
A
5
B
8
RT
6
Y
7
Z
D
7 RE
DI
LOGIC
DEVICE
(µP, ASIC,
UART)
3
DE 2
GND
GND
2
4, 5
Test Circuits and Waveforms
VCC OR VL
RL/2
DE
VCC OR VL
Z
DI
DI
VOD
D
375Ω
DE
Z
VOD
D
VCM
RL = 60Ω
-7V TO +12V
Y
Y
RL/2
VOC
375Ω
FIGURE 1B. VOD WITH COMMON MODE LOAD
FIGURE 1A. VOD AND VOC
FIGURE 1. DC DRIVER TEST CIRCUITS
3V OR VL
DI
50%
50%
0V
tSD2
tSD1
VOH
OUT (Z)
50%
VOL
OUT (Y)
DE
VCC OR VL
50%
tDDLH
Z
DI
RDIFF
D
Y
SIGNAL
GENERATOR
CD
DIFF OUT (Y - Z)
tDDHL
90%
50%
10%
90%
50%
10%
tR
tSSK = |tSD1(Y) - tSD2(Y)| OR |tSD1(Z) - tSD2(Z)|
FIGURE 2A. TEST CIRCUIT
+VOD
-VOD
tF
tDSK = |tDDLH - tDDHL|
FIGURE 2B. MEASUREMENT POINTS
FIGURE 2. DRIVER PROPAGATION DELAY AND DIFFERENTIAL TRANSITION TIMES
3
FN7607.1
July 28, 2011
ISL3298EMRTEP
Test Circuits and Waveforms (Continued)
DE
Z
DI
500Ω
VCC
D
SIGNAL
GENERATOR
SW
Y
3V OR VL
DE
50%
50%
GND
0V
50pF
tZH
OUTPUT HIGH
OUTPUT
DI
SW
tHZ
Y/Z
1/0
GND
tLZ
Y/Z
0/1
VCC
tZH
Y/Z
1/0
GND
tZL
Y/Z
0/1
VCC
VOH - 0.25V
50%
OUT (Y, Z)
PARAMETER
tHZ
VOH
0V
tZL
tLZ
VCC
OUT (Y, Z)
50%
VOL + 0.25V V
OUTPUT LOW
OL
FIGURE 3B. MEASUREMENT POINTS
FIGURE 3A. TEST CIRCUIT
FIGURE 3. DRIVER ENABLE AND DISABLE TIMES
VCC OR VL
3V OR VL
DE
+
Z
DI
54Ω
D
Y
CD
DI
0V
VOD
-
SIGNAL
GENERATOR
+VOD
DIFF OUT (Y - Z)
-VOD
0V
FIGURE 4B. MEASUREMENT POINTS
FIGURE 4A. TEST CIRCUIT
FIGURE 4. DRIVER DATA RATE
4
FN7607.1
July 28, 2011
ISL3298EMRTEP
Applications 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
transmitters and receivers 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. To allow for multipoint operation, the
RS-485 specification requires that drivers must handle bus
contention without sustaining any damage.
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.
VCC = +3.3V
DI
DE
The ISL3298EMRTEP’s output transition times allow data rates
of at least 16Mbps.
Wide Supply Range
VOH ≤ 2V
VIH ≥ 2V
VOH ≤ 2V
ISL3293E
TXD
DEN
GND
UART/PROCESSOR
VCC = +3.3V
VCC = +2V
VL
Driver Features
The driver is tri-statable via the active high DE input. If the Tx
enable function isn’t needed, tie DE to VCC (or VL) through a 1kΩ
to 3kΩ resistor.
VIH ≥ 2V
GND
DI
This RS-485/RS-422 driver is a differential output device that
delivers at least 1.5V across a 54Ω load (RS-485), and at least 2V
across a 100Ω load (RS-422). The drivers feature low propagation
delay skew to maximize bit width, and to minimize EMI.
VCC = +2V
DE
VIH = 1.4V
TXD
VOH ≤ 2V
VIH = 1.4V
GND
ISL3296E
VOH ≤ 2V
DEN
GND
UART/PROCESSOR
FIGURE 5. USING VL PIN TO ADJUST LOGIC LEVELS
Logic Supply (VL Pin)
Note: Power-up VCC before powering up the VL supply.
The ISL3298EMRTEP is optimized for 3.3V operation, but can
be operated with supply voltages as high as 5.5V. This device
meets the RS-422 and RS-485 specifications for supply
voltages less than 4V, and is RS-422 and RS-485 compatible
for supplies greater than 4V. Operation at +125°C requires VCC
≤ 3.6V, while 5V operation requires adding output current
limiting resistors (as described in the “Driver Overload
Protection” on page 6) if output short circuits (e.g., from bus
contention) are a possibility.
5.5V Tolerant Logic Pins
Logic input pins (DI, DE) contain no ESD nor parasitic diodes to
VCC (nor to VL), so they withstand input voltages exceeding 5.5V
regardless of the VCC and VL voltages (see Figure 5).
The ISL3298EMRTEP includes a VL pin that powers the logic
inputs (DI and DE). These pins interface with “logic” devices such
as UARTs, ASICs, and µcontrollers, and today most of these
devices use power supplies significantly lower than 3.3V. Thus,
the logic device’s low VOH might not exceed the VIH of a 3.3V or
5V powered DI or DE input. Connecting the VL pin to the power
supply of the logic device (as shown in Figure 5) reduces the DI
and DE input switching points to values compatible with the logic
device’s output levels. Tailoring the logic pin input switching
points and output levels to the supply voltage of the UART, ASIC,
or µcontroller eliminates the need for a level shifter/translator
between the two ICs.
VL can be anywhere from VCC down to 1.35V, but the input
switching points may not provide enough noise margin, and
16Mbps data rates may not be achievable, when VL < 1.5V. The
E.C. table in the SMD indicates typical VIH and VIL values for
various VL settings so the user can ascertain whether or not a
particular VL voltage meets his/her needs.
The VL supply current (IL) is typically much less than 20µA, as
shown in Figure 9, when DE and DI are above/below VIH/VIL.
5
FN7607.1
July 28, 2011
ISL3298EMRTEP
Hot Plug Function
Driver Overload Protection
When a piece of equipment powers-up, there is a period of time
where the processor or ASIC driving the RS-485 control line (DE)
is unable to ensure that the RS-485 Tx outputs are kept disabled.
If the equipment is connected to the bus, a driver activating
prematurely during power up may crash the bus. To avoid this
scenario, the ISL3298EMRTEP incorporates a “Hot Plug” function.
During power-up, circuitry monitoring VCC ensures that the Tx
outputs remain disabled for a period of time, regardless of the state
of DE. This gives the processor/ASIC a chance to stabilize and drive
the RS-485 control lines to the proper states.
As stated previously, the RS-485 specification requires that
drivers survive worst case bus contentions undamaged. These
drivers meet this requirement, for VCC ≤ 3.6V, via driver output
short circuit current limits, and on-chip thermal shutdown
circuitry.
ESD Protection
All pins on this device includes class 3 (8kV) Human Body
Model (HBM) ESD protection structures, but the RS-485 pins
(driver outputs) incorporate advanced structures allowing it to
survive ESD events in excess of ±16.5kV HBM and ±7kV to the
IEC61000 contact test method. 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 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. Devices operating at 16Mbps are
limited to lengths less than 100’.
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 receivers in
these ICs. Proper termination is imperative, to minimize
reflections.
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.
6
The driver output stages incorporate short circuit current limiting
circuitry which ensures that the output current never exceeds the
RS-485 specification, for VCC ≤ 3.6V, even at the common mode
voltage range extremes. Additionally, these devices utilize a
foldback circuit which reduces the short circuit current, and thus
the power dissipation, whenever the contending voltage exceeds
either VCC or GND.
In the event of a major short circuit condition, devices also include
a thermal shutdown feature that disables the drivers whenever the
die temperature becomes excessive. This eliminates the power
dissipation, allowing the die to cool. The drivers automatically
re-enable after the die temperature drops about +20°C. If the
contention persists, the thermal shutdown/re-enable cycle repeats
until the fault is cleared.
At VCC > 3.6V, the instantaneous short circuit current is high enough
that output stage damage may occur during short circuit conditions
to voltages outside of GND to VCC, before the short circuit limiting
and thermal shutdown activate. For VCC = 5V operation, if output
short circuits are a possibility (e.g., due to bus contention), it is
recommended that a 5Ω resistor be inserted in series with each
output. This resistor limits the instantaneous current below levels
that can cause damage. The driver VOD at VCC = 5V is so large that
this small added resistance has little impact.
High Temperature Operation
Due to power dissipation and instantaneous output short circuit
current levels at VCC = 5V, these transmitters may not be
operated at +125°C with VCC > 3.6V.
At VCC = 3.6V, the device may be operated at +125°C, while
driving a 100’, double terminated, CAT 5 cable at 16Mbps,
without triggering the thermal SHDN circuit.
Low Power Shutdown Mode
This BiCMOS transmitter uses a fraction of the power required by
its bipolar counterparts and it also includes a shutdown feature
that reduces the already low quiescent ICC to a 1µA trickle. This
device enters shutdown whenever the driver disables (DE = GND).
FN7607.1
July 28, 2011
ISL3298EMRTEP
Typical Performance Curves
VCC = VL = 3.3V, TA = +25°C; Unless Otherwise Specified
3.5
DRIVER OUTPUT CURRENT (mA)
100
DIFFERENTIAL OUTPUT VOLTAGE (V)
110
+85°C
90
80
+25°C
70
60
50
+125°C
40
30
20
10
0
0
0.5
1.0
1.5
2.0
2.5
3.0
DIFFERENTIAL OUTPUT VOLTAGE (V)
RDIFF = 100Ω, VL = VCC = 5.0V, H
2.9
2.7 RDIFF = 54Ω, VL = VCC = 5.0V, H
RDIFF = 54Ω, VL = VCC = 5.0V, L
2.5
RDIFF = 100Ω, VL= VCC = 3.3V, L
2.3
2.1
RDIFF = 100Ω, VL = VCC = 3.3V, H
RDIFF = 54W,VL = VCC = 3.3V, L
1.9
1.7
RDIFF = 54Ω, VL= VCC = 3.3V, H
-55
-35
-15
5
25
45
65
TEMPERATURE (°C)
85
105
125
FIGURE 7. DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs
TEMPERATURE
FIGURE 6. DRIVER OUTPUT CURRENT vs DIFFERENTIAL
OUTPUT VOLTAGE
105
40
104
VCC = 3.3V
35
103
VCC = 5.0V, DI = L
102
VL = 3.3V
30
25
101
IL (µA)
ICC (µA)
3.1
1.5
3.5
RDIFF = 100Ω, VL = VCC = 5.0V, L
3.3
VCC = 5.0V, DI = H
100
99
98
20
VL = 2.5V
15
10
97
5
96
95
-55
0
-35
-15
5
25
45
65
TEMPERATURE (°C)
85
105
125
1
2
3
4
5
6
7 7.5
FIGURE 9. VL SUPPLY CURRENT vs LOGIC PIN VOLTAGE
31
200
150
29
PROPAGATION DELAY (ns)
OUTPUT CURRENT (mA)
0
DI VOLTAGE (V)
FIGURE 8. SUPPLY CURRENT vs TEMPERATURE
100
Y OR Z = LOW
50
0
-50
-100
-150
VL ≤ 2V
-7 -6
-4
-2
0
2
4
6
OUTPUT VOLTAGE (V)
8
10
FIGURE 10. DRIVER OUTPUT CURRENT vs SHORT CIRCUIT
VOLTAGE
7
12
VL = VCC ≥ 3.3V,SKEW
27
25
VL = VCC ≤ 3.3V, SKEW
23
21
19
-55
-35
-15
5
25
45
65
TEMPERATURE (°C)
85
105
125
FIGURE 11. DRIVER DIFFERENTIAL PROPAGATION DELAY vs
TEMPERATURE
FN7607.1
July 28, 2011
ISL3298EMRTEP
VCC = VL = 3.3V, TA = +25°C; Unless Otherwise Specified (Continued)
0.7
3.5
0.6
3.0
2.5
0.5
SKEW (ns)
0.4
SKEW (ns)
VL = VCC ≤ 3.3V, SKEW
0.3
1.5
0.2
1.0
0.1
0.5
0.0
-55
-35
-15
5
25
45
65
85
105
Y, VL = VCC = 3.3V, SKEW
2.0
Z, VL = VCC = 3.3V, SKEW
0.0
-55
125
-35
TEMPERATURE (°C)
FIGURE 12. DRIVER DIFFERENTIAL SKEW vs TEMPERATURE
PROPAGATION DELAY (ns)
30
28
26
Y, VL = VCC = TDDHL
24
Y, VL = VCC, TDDLH
22
20
18
-55
Z, VL = VCC = TDDHL
-35
-15
5
25
45
65
TEMPERATURE (°C)
85
105
125
FIGURE 14. SINGLE-ENDED PROPAGATION DELAY vs
TEMPERATURE
DRIVER OUTPUT (V)
Z, VL = VCC, TDDLH
5
25
45
65
TEMPERATURE (°C)
85
105
125
FIGURE 13. DRIVER SINGLE-ENDED SKEW vs TEMPERATURE
DRIVER OUTPUT (V)
32
-15
RDIFF = 54Ω, CD = 50pF
VL = 1.35V
DI
3.0
1.5
Z
0
Y
0
3
2
1
0
-1
-2
-3
3
DRIVER INPUT (V)
Typical Performance Curves
Y-Z
TIME (10ns/DIV)
FIGURE 15. DRIVER WAVEFORMS, HIGH TO LOW
Die Characteristics
SUBSTRATE AND TDFN THERMAL PAD POTENTIAL
(POWERED UP):
GND
TRANSISTOR COUNT:
516
PROCESS:
Si Gate BiCMOS
8
FN7607.1
July 28, 2011
ISL3298EMRTEP
Revision History
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to web to make
sure you have the latest Rev.
DATE
REVISION
7/28/11
FN7607.1
CHANGE
Changed in Features “Specifications per DSCC” to “Specifications per DLA” to match website.
1/27/11
3/30/10
In Figure 8 on page 7, corrected units in y axis from mA to µA.
FN7607.0
Initial Release.
Products
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9
FN7607.1
July 28, 2011
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