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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
DESCRIPTION
• Full-Duplex RS-485 and RS-422 Transceivers
• Operates from a single +3.3V Supply
• Interoperable with +5.0V logic
• Driver/Receiver Tri-state Enable Lines (SP3491)
• -7V to +12V Common-Mode Input Voltage Range
• +/-200mV Receiver Input Sensitivity
• Allows up to 32 transceivers on the serial bus
• Compatability with LTC490 and SN75179 (SP3490)
• Compatability with LTC491 and SN75180 (SP3491)
SP3490/SP3491
+3.3V Low Power Full-Duplex RS-485
Transceivers with 10Mbps Data Rate
V
CC
D
RA
B
Z
Y
R
GND
2
1
3
4
5
6
7
8
D
The SP3490 and SP3491 devices are +3.3V low power full-duplex transceivers that meet
the specications of the RS-485 and RS-422 serial protocols. These devices are pin-to-pin
compatible with the Exar SP490 and SP491 devices as well as popular industry standards.
The SP3490 and SP3491 feature Exar's BiCMOS process, allowing low power operation
without sacricing performance. The SP3490 and SP3491 meet the electrical specications
of the RS-485 and RS-422 serial protocols up to 10Mbps under load. The SP3491 is identical
to the SP3490 with the addition of driver and reciveiver tri-state enable lines.
SP3490
VCC
D
R
NC
A
B
Z
Y
R
NC
NC
DE
REB
GND
GND
2
1
3
4
5
6
78
9
10
11
12
13
14
D
SP3491
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation
of the device at these ratings or any other above those
indicated in the operation sections of the specications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may
affect reliability.
VCC.....................................................................+6.0V
Input Voltages
Logic....................................-0.3V to +6.0V
Drivers.................................-0.3V to +6.0V
Receivers.........................................+/-14V
Output Voltages
Drivers.............................................+/-14V
Receivers............................-0.3V to +6.0V
Storage Temperature.......................-65˚C to +150˚C
Power Dissipation
8-pin NSOIC...................................................600mW
(derate 6.90mW/ºC above +70ºC)
14-pin NSOIC.................................................700mW
(derate 8.33mW/ºC above +70ºC)
ELECTRICAL CHARACTERISTICS
TAMB = TMIN to TMAX and VCC = +3.3V +/-5% unless otherwise noted.
PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
SP3490 DRIVER
DC Characteristics
Differential Output Voltage GND Vcc Volts Unloaded; R = ∞Ω ; Figure 1
Differential Output Voltage 2 Vcc Volts With Load; R = 50Ω (RS-422);
Figure 1
Differential Output Voltage 1.5 Vcc Volts With Load; R = 27Ω (RS-485);
Figure 1
Change in Magnitude of Driver
Differential Output Voltage for
Complimentary states
0.2 Volts R = 27Ω or R = 50Ω; Figure 1
Driver Common Mode Output
Voltage
3 Volts R = 27Ω or R = 50Ω; Figure 1
Input High Voltage 2.0 Volts
Input Low Voltage 0.8 Volts
Input Current +/-10 µA
Driver Short Circuit Current
VOUT = HIGH +/-250 mA -7V ≤ VO ≤ +12V; Figure 8
VOUT = LOW +/-250 mA -7V ≤ VO ≤ +12V; Figure 8
SP3490 DRIVER
AC Characteristics
Max. Transmission Rate 10 Mbps
Driver Input to Output, tPLH 20 40 60 ns R = 27Ω, Figures 2 & 9
Driver Input to Output, tPHL 20 40 60 ns R = 27Ω, Figures 2 & 9
Differential Driver Skew 2 ns |tPHL(Y)- tPLH(Y)|, |tPHL(Z)- tPLH(Z)|,
Figures 2 and 9
Driver Rise or Fall Time 5 20 ns From 10%-90%; Figures 3 and 10
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
SP3490 RECEIVER
DC Characteristics
Differential Input Threshold -0.2 +0.2 Volts -7V ≤ VCM ≤ +12V
Input Hysteresis 25 mV VCM = 0V
Output Voltage HIGH Vcc-0.4 Volts IO = -1.5mA, VID = +200mV
Output Voltage LOW 0.4 Volts IO = +2.5mA, VID = -200mV
Input Resistance 12 15 kΩ -7V ≤ VCM ≤ +12V
Input Current (A, B); VIN = 12V +1.0 mA VIN = 12V
Input Current (A, B); VIN = -7V -0.8 mA VIN = -7V
Short Circuit Current 60 mA 0V ≤ VO ≤ VCC
SP3490 RECEIVER
AC Characteristics
Max. Transmission Rate 10 Mbps
Receiver Input to Output, tPLH 40 70 120 ns Figures 6 and 12
Receiver Input to Output, tPLH 85 ns TAMB = +25°C, Vcc = 3.3V Figures
6 and 12
Receiver Input to Output, tPHL 40 70 120 ns Figures 6 and 12
Receiver Input to Output, tPHL 85 ns TAMB = +25°C, Vcc = 3.3V Figures
6 and 12
Differential Receiver Skew 4 ns |tPHL(A)- tPLH(A)|, |tPHL(B)- tPLH(B)|,
Figures 6 and 12
POWER REQUIREMENTS
Supply Voltage 3.0 3.3 3.6 V
Supply Current 1000 2000 µA D = 0V or VCC
ESD Protection for D, R, A, B,
Y and Z pins
+/-2 kV Human Body Model
ELECTRICAL CHARACTERISTICS
TAMB = TMIN to TMAX and VCC = +3.3V +/-5% unless otherwise noted.
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
ELECTRICAL CHARACTERISTICS
TAMB = TMIN to TMAX and VCC = +3.3V +/-5% unless otherwise noted.
PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
SP3491 DRIVER
DC Characteristics
Differential Output Voltage GND Vcc Volts Unloaded; R = ∞Ω ; Figure 1
Differential Output Voltage 2 Vcc Volts With Load; R = 50Ω (RS-422);
Figure 1
Differential Output Voltage 1.5 Vcc Volts With Load; R = 27Ω (RS-485);
Figure 1
Change in Magnitude of Driver
Differential Output Voltage for
Complimentary states
0.2 Volts R = 27Ω or R = 50Ω; Figure 1
Driver Common Mode Output
Voltage
3 Volts R = 27Ω or R = 50Ω; Figure 1
Input High Voltage 2.0 Volts Applies to DE, D, REB
Input Low Voltage 0.8 Volts Applies to DE, D, REB
Input Current +/-10 µA Applies to DE, D, REB
Driver Short Circuit Current
VOUT = HIGH +/-250 mA -7V ≤ VO ≤ +12V; Figure 8
VOUT = LOW +/-250 mA -7V ≤ VO ≤ +12V; Figure 8
SP3491 DRIVER
AC Characteristics
Max. Transmission Rate 10 Mbps
Driver Input to Output, tPLH 20 40 60 ns Figures 2 & 9
Driver Input to Output, tPHL 20 40 60 ns Figures 2 & 9
Differential Driver Skew 2 ns |tPHL(Y)- tPLH(Y)|, |tPHL(Z)- tPLH(Z)|,
Figures 2 and 9
Driver Rise or Fall Time 5 20 ns From 10%-90%; Figures 3 and 10
Driver Enable to Output HIGH 52 120 ns Figures 4 and 11
Driver Enable to Output LOW 60 120 ns Figures 5 and 11
Driver Disable from LOW 40 120 ns Figures 5 and 11
Driver Disable from HIGH 60 120 ns Figures 4 and 11
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
SP3491 RECEIVER
DC Characteristics
Differential Input Threshold -0.2 +0.2 Volts -7V ≤ VCM ≤ +12V
Input Hysteresis 25 mV VCM = 0V
Output Voltage HIGH Vcc-0.4 Volts IO = -1.5mA, VID = +200mV
Output Voltage LOW 0.4 Volts IO = +2.5mA, VID = -200mV
Three-State ( High Impedance)
Output Current
+/-1 µA 0V ≤ VO ≤ Vcc; REB = Vcc
Input Resistance 12 15 kΩ -7V ≤ VCM ≤ +12V
Input Current (A, B); VIN = 12V +1.0 mA DE = 0V, VCC = 0V or 3.6V,
VIN = 12V
Input Current (A, B); VIN = -7V -0.8 mA DE = 0V, VCC = 0V or 3.6V,
VIN = -7V
Short Circuit Current 60 mA 0V ≤ VO ≤ VCC
SP3491 RECEIVER
AC Characteristics
Max. Transmission Rate 10 Mbps REB = 0V, DE = 0V
Receiver Input to Output, tPLH 40 70 120 ns Figures 6 and 12
Receiver Input to Output, tPLH 85 ns TAMB = +25°C, Vcc = 3.3V, Figures
6 and 12
Receiver Input to Output, tPHL 40 70 120 ns Figures 6 and 12
Receiver Input to Output, tPHL 85 ns TAMB = +25°C, Vcc = 3.3V, Figures
6 and 12
Differential Receiver Skew 4 ns |tPHL(A)- tPLH(A)|, |tPHL(B)- tPLH(B)|,
Figures 6 and 12
Receiver Enable to Output
LOW
65 150 ns Figures 7 and 13; S1 Closed, S2
open
Receiver Enable to Output
HIGH
65 150 ns Figures 7 and 13; S2 Closed, S1
open
Receiver Disable from LOW 65 200 ns Figures 7 and 13; S1 Closed, S2
open
Receiver Disable from HIGH 65 200 ns Figures 7 and 13; S2 Closed, S1
open
POWER REQUIREMENTS
Supply Voltage +3.0 +3.6 V
Supply Current 1000 2000 µA REB, D = 0V or VCC; DE = VCC
Supply Current 800 1500 µA DE = 0V
ESD Protection for R, D, DE,
REB, A, B, Y and Z pins
+/-2 kV Human Body Model
ELECTRICAL CHARACTERISTICS
TAMB = TMIN to TMAX and VCC = +3.3V +/-5% unless otherwise noted.
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
PIN FUNCTION
VCC
D
RA
B
Z
Y
R
GND
2
1
3
4
5
6
7
8
D
Pin 1 - Vcc - Positive supply +3.00V < Vcc < +3.60V
Pin 2 - R - Receiver output
Pin 3 - D - Driver input
Pin 4 - GND - Ground connection
Pin 5 - Y - Non-inverting driver output
Pin 6 - Z - Inverting driver output
Pin 7 - B - Inverting receiver Input
Pin 8 - A - Non-inverting receiver input
SP3490 Pin Function SP3490
VCC
D
R
NC
A
B
Z
Y
R
NC
NC
DE
REB
GND
GND
2
1
3
4
5
6
78
9
10
11
12
13
14
D
Pin 1 - NC - No connect
Pin 2 - R - Receiver output
Pin 3 - REB - Receiver cutput enable active LOW
Pin 4 - DE - Driver output enable active HIGH
Pin 5 - D - Driver input
Pin 6 - GND - Ground connection
Pin 7 - GND - Ground connection
Pin 8 - NC - No connect
Pin 9 - Y - Non-inverting driver output
Pin 10 - Z - Inverting driver output
Pin 11 - B - Inverting receiver Input
Pin 12 - A - Non-Inverting receiver input
Pin 13 - NC - No connect
Pin 14 - Vcc - Positive supply +3.00V < Vcc < +3.60V
SP3491 Pin Function SP3491
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
TEST CIRCUITS
R
RV
OC
D
Vcc
V
OD
Figure 1. Driver DC Test Load Circuit
GENERATOR
(NOTE 1) 50Ω
C
L
OUT
D
V
CC
R
L
=
60Ω
C
L
= 15pF (NOTE 2)
Figure 3. Driver Differential Output Delay and
Transition Time Circuit.
GENERATOR
(NOTE 1) 50Ω
S1
R
L
= 110Ω
OUT
C
L
= 50pF
(NOTE 2)
V
OM
= ≈ 1.5V
V
OH
+ V
OL
2
D
Figure 4. Driver Enable and Disable Timing Circuit,
Output High
Figure 2. Driver Propagation Delay Test Circuit
GENERATOR
(NOTE 1) 50Ω
V
CC
S1
V
DM
R
L
= 27Ω
OUT
C
L
= 15pF
(NOTE 2)
V
OM
= ≈ 1.5V
V
OH
+ V
OL
2
D
Figure 5. Driver Enable and Disable Timing Circuit,
Output Low
GENERATOR
(NOTE 1) 50Ω
S1
RL = 110Ω
OUT
CL = 50pF
(NOTE 2)
D
0V OR 3V
VCC
GENERATOR
(NOTE 1)
50Ω
1.5V
0V
V
ID
ROUT
C
L
= 15pF
(NOTE 2)
V
OM
= V
CC
2
Figure 6. Receiver Propagation Delay Test Circuit
1.5V
-1.5V
S3
VID
GENERATOR
(NOTE 1)
50Ω
CL
= 15pF
(NOTE 2)
R
1k
S1
S2
VCC
A/Y
D
DI = 0 or Vcc
B/Z
DE = 0 or Vcc
I
OS D
100Ω
-7V to +12V V
Figure 7. Receiver Enable and Disable Timing
Circuit
Figure 8. Driver Short Circuit Current Limit Test
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
Figure 9. Driver Propagation Delay Waveforms
0V
V
OH
t
PLH
t
PHL
VOM
t
PHL
t
PLH
3V
V
OL
V
OH
1.5V 1.5V
INPUT
Y OUTPUT
VOM
Z OUTPUT
V
OL
VOM
VOM
VOM = VOH + VOL
2≈ 1.5V
SWITCHING WAVEFORMS
Figure 13. Receiver Enable and Disable Waveforms
IN 1.5V
tDO1
1.5V
tDO2
3V
0V
OUT
50% 50%
10% 10%
90% 90%
tTD tTD
2.0V
-2.0V
Figure 10. Driver Differential Output Delay and
Transition Time Waveforms
0V
VOH
tPZH
0.25V
tPHZ
V
OM
tPZL tPLZ
3V
VOL
VCC
1.5V 1.5V
DE
OUTPUT
HIGH
V
OM
0.25V
0V
OUTPUT
LOW
V
OM
= V
OH
+ V
OL
2≈ 1.5V
3V
0V
V
CC
t
RPLH
1.5V
t
RPHL
V
OM
V
OM
0V
1.5V
INPUT
OUTPUT
VOM = VCC
2
Figure 12. Receiver Propagation Delay WaveformsFigure 11. Driver Enable and Disable Timing
Waveforms
3V
0V
t
PRHZ
1.5V
t
PRZH
t
PRSH
1.5V
1.5V
10%
0V
V
OH
REB
OUTPUT
S1 is open
S2 is closed
S3 = 1.5V
3V
0V
t
PRLZ
1.5V
t
PRZL
t
PRSL
1.5V
1.5V
10%
V
CC
REB
OUTPUT
S1 is closed
S2 is open
S3 = -1.5V
V
OL
NOTE 1: The input pulse is supplied by a generator with the following characteristics:
PRR = 250kHz, 50% duty cycle, tR < 6.0ns, ZO = 50Ω.
NOTE 2: CL includes probe and stray capacitance.
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
The SP3490 and SP3491 are two members
in the family of +3.3V low power full-du-
plex transceivers that meet the electrical
specications of the RS-485 and RS-422
serial protocols. These devices are pin-to-
pin compatible with the Exar SP490 and
SP491 devices as well as popular industry
standards. The SP3490 and SP3491 feature
Exar's BiCMOS process allowing low power
operation without sacricing performance.
The RS-485 standard is ideal for multi-drop
applications and for long-distance interfaces.
RS-485 allows up to 32 drivers and 32 receiv-
ers to be connected to a data bus, making it
an ideal choice for multi-drop applications.
Since the cabling can be as long as 4,000
feet, RS-485 transceivers are equipped with
a wide (-7V to +12V) common mode range
to accommodate ground potential differ-
ences. Because RS-485 is a differential
interface, data is virtually immune to noise
in the transmission line.
Drivers
The drivers for both the SP3490 and SP3491
have differential outputs. The typical voltage
output swing with no load will be 0 volts to Vcc.
With worst case loading of 54Ω across the
differential outputs, the drivers can maintain
greater than 1.5V voltage levels.
The driver of the SP3491 has a driver en-
able control line which is active HIGH. A
logic HIGH on DE (pin 4) of the SP3491
will enable the differential driver outputs. A
logic LOW on the DE(pin 4) will tri-state the
driver outputs. The SP3490 does not have
a driver enable.
Receivers
The receivers of the SP3490 and SP3491
have differential inputs with an input sensi-
tivity of ±200mV. Input impedance of the
receivers is typically 15kΩ (12kΩ minimum).
A wide common mode range of -7V to +12V
allows for large ground potential differences
between systems. The receivers for both the
SP3490 and SP3491 are equipped with a
fail-safe feature that guarantees the receiver
output will be in a HIGH state when the input
is left unconnected.
The receiver of the SP3491 has a enable
control line which is active LOW. A logic
LOW on REB (pin 3) of the SP3491 will en-
able the differential receiver. A logic HIGH
on REB (pin 3) of the SP3491 will tri-state
the receiver.
DESCRIPTION
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
11
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3490_3491_102_102710
ORDERING INFORMATION
Model Temperature Range Package Types
SP3490CN-L ....................................................................... 0°C to +70°C ................................................................................................8-pin NSOIC
SP3490CN-L/TR ................................................................. 0°C to +70°C ................................................................................................8-pin NSOIC
SP3490EN-L...................................................................... -40°C to +85°C...............................................................................................8-pin NSOIC
SP3490EN-L/TR................................................................. -40°C to +85°C.............................................................................................8-pin NSOIC
SP3491CN-L ....................................................................... 0°C to +70°C ..............................................................................................14-pin NSOIC
SP3491CN-L/TR ................................................................. 0°C to +70°C ..............................................................................................14-pin NSOIC
SP3491EN-L...................................................................... -40°C to +85°C.............................................................................................14-pin NSOIC
SP3491EN-L/TR................................................................. -40°C to +85°C............................................................................................14-pin NSOIC
REVISION HISTORY
DATE REVISION DESCRIPTION
10/11/02 -- Legacy Sipex Datasheet
06/08/10 1.0.0 Convert to Exar Format. Update ordering information as a result of discontinued
Lead type package options per PDN 081126-01. Change revision to 1.0.0. Add new
Figure 8 - Driver Short Circuit Current Limit Test Circuit
9/14/10 1.0.1 Correct package type for SP3491 options in ordering table from 8 pin NSOIC to 14
pin NSOIC
10/27/10 1.0.2 Add ESD protection levels of +/-2kV. Remove SP3490 Supply Current rating for DE
= 0V (No driver enable for SP3490).
Notice
EXAR Corporation reserves the right to make changes to any products contained in this publication in order to improve design, performance or reliabil-
ity. EXAR Corporation assumes no representation that the circuits are free of patent infringement. Charts and schedules contained herein are only for
illustration purposes and may vary depending upon a user's specic application. While the information in this publication has been carefully checked;
no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can
reasonably be expected to cause failure of the life support system or to signicantly affect its safety or effectiveness. Products are not authorized for
use in such applications unless EXAR Corporation receives, in writting, assurances to its satisfaction that: (a) the risk of injury or damage has been
minimized ; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Copyright 2010 EXAR Corporation
Datasheet October 2010
For technical support please email Exar's Serial Technical Support group at: serialtechsupport@exar.com
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
Note: /TR = Tape and Reel
