3.3V Low Power Half-Duplex RS-485 Transceiver
with 10Mbps Data Rate
SP3485
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REV 2.0.1
FEATURES
RS-485 and RS-422 transceiver
Operates from a single 3.3V supply
Interoperable with 5.0V logic
Driver/receiver enable
-7V to +12V common-mode input voltage
range
Allows up to 32 transceivers on the serial
bus
Compatibility with industry standard 75176
pinout
Driver output short-circuit protection
Description
The SP3485 device is a 3.3V low power half-duplex transceiver that
meets the specifications of the RS-485 and RS-422 serial protocols.
This device is pin-to-pin compatible with the MaxLinear SP481,
SP483 and SP485 devices as well as popular industry standards. The
SP3485 can meet the electrical specifications of the RS-485 and RS-
422 serial protocols up to 10Mbps under load.
Block Diagram
RO 1
RE 2
DE 3
DI 4
VCC
8
B7
A6
GND5
D
R
Ordering Information - Back Page
SP3485
SP3485
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REV 2.0.1
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 specifications 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 ...........................................±15V
Output Voltages
Drivers ...............................................±15V
Receivers .............................. -0.3V to 6.0V
Electrical Characteristics
Unless otherwise noted: TAMB = TMIN to TMAX and VCC = 3.3V ±5%.
PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
SP3485 Driver DC Characteristics
Differential output voltage 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, DI, RE
Input low voltage 0.8 Volts Applies to DE, DI, RE
Input current ±10 µA Applies to DE, DI, RE
Driver short circuit current VOUT = HIGH ±250 mA -7V ≤ VO ≤ +12V; Figure 8
Driver short circuit current VOUT = LOW ±250 mA -7V ≤ VO ≤ +12V; Figure 8
SP3485 Driver AC Characteristics
Maximum data rate 10 Mbps RE = VCC, DE = VCC
Driver input to output, tPLH 17 60 ns Figures 2 & 9
Driver input to output, tPHL 17 60 ns Figures 2 & 9
Differential driver skew 2 10 ns
|
tDO1- tDO2
|
, Figures 2 and 10
Driver rise or fall time 5 20 ns From 10%-90%; Figures 3 and 10
Driver enable to output high 35 120 ns Figures 4 and 11
Driver enable to output low 30 120 ns Figures 5 and 11
Driver disable time from low 20 120 ns Figures 5 and 11
Driver disable time from high 20 120 ns Figures 4 and 11
Driver enable from shutdown to output high, tPSH 250 ns CL = 50pF, RL = 500Ω.
Figures 4, 5, and 11
Driver enable from shutdown to output low, tPSL 250 ns
Time to shutdown, tSHDN 50 200 600 ns Notes 1 and 2
Storage Temperature ...................................-65˚C to 150˚C
Maximum Junction Temperature, TJ ..........................125˚C
Power Dissipation .................................................... 600mW
(derate 6.90mW/°C above 70°C)
Operating Conditions
Package Power Dissipation
8-pin NSOIC ѲJA ................................................ 128.4˚C/W
ESD Rating
Human Body Model (HBM) .......................................... ±2kV
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PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
SP3485 Receiver DC Characteristics
Differential input threshold -0.2 0.2 Volts -7V ≤ VCM ≤ 12V
Input hysteresis 20 mV VCM = 0V
Output voltage HIGH Vcc-0.4 Volts VID = 200mV, -1.5mA
Output voltage LOW 0.4 Volts VID = -200mV, 2.5mA
Three-state (high impedance) output current ±1µA 0V ≤ VO ≤ VCC; RE = VCC
Input resistance 12 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 7 60 mA 0V ≤ VCM ≤ VCC
SP3485 Receiver AC Characteristics
Maximum data rate 10 Mbps RE = 0V, DE = 0V
Receiver input to output, tPLH 40 100 ns Figures 6 and 12
Receiver input to output, tPLH 70 ns TAMB = 25°C, Vcc = 3.3V,
Figures 6 and 12
Receiver input to output, tPHL 35 100 ns Figures 6 and 12
Receiver input to output, tPHL 70 ns TAMB = 25°C, Vcc = 3.3V,
Figures 6 and 12
Differential receiver skew 4ns tRSKEW =
|
tRPHL- tRPLH
|
,
Figures 6 and 12
Receiver enable to output low 10 60 ns Figures 7 and 13,
S1 closed, S2 open
Receiver enable to output high 10 60 ns Figures 7 and 13,
S2 closed, S1 open
Receiver disable from low 10 60 ns Figures 7 and 13,
S1 closed, S2 open
Receiver disable from high 10 60 ns Figures 7 and 13,
S2 closed, S1 open
Receiver enable from shutdown to output high,
tPRSH
1800 ns CL = 15pF, RL = 1kΩ.
Figures 7 and 13
Receiver enable from shutdown to output low, tPRSL 1800 ns
Time to shutdown, tSHDN 50 200 600 ns Notes 1 and 2
Power Requirements
Supply current , no load 425 2000 µA RE, DI = 0V or VCC ; DE = VCC
Supply current , no load 300 1500 µA RE = 0V, DI = 0V or VCC, DE = 0V
NOTES:
1. The transceivers are put into shutdown by gringing RE high and DE low simultaneously for at least 600ns. If the control inputs are in this state for less than 50ns, the
device is guaranteed to not enter shutdown. If the enable inputs are held in this state for at least 600ns, the device is assured to be in shutdown. Note that the receiver
and driver times increase significantly when coming out of shutdown.
2. This spec is guaranteed by design and bench characterization.
Electrical Characteristics (Continued)
Unless otherwise noted: TAMB = TMIN to TMAX and VCC = 3.3V ±5%.
SP3485
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Pin Functions
Pin Name Description
1 RO Receiver output
2 RE Receiver output enable active LOW
3 DE Driver output enable active HIGH
4 DI Driver input
5 GND Ground connection
6 A Non-inverting driver output / receiver input
7 B Inverting driver output / receiver input
8 VCC Positive supply
RO 1
RE 2
DE 3
DI 4
VCC
8
B7
A6
GND5
D
R
SP3485
Pinout (Top View)
SP3485
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Test Circuits
Figure 1: Driver DC Test Load Circuit Figure 2: Driver Propagation Delay Test Circuit
Figure 3: Driver Differential Output Delay
and Transition Time Circuit.
Figure 4: Driver Enable and Disable Timing Circuit,
Output High
Figure 5: Driver Enable and Disable Timing Circuit,
Output Low
Figure 6: Receiver Propagation Delay Test Circuit
Figure 7: Receiver Enable and Disable Timing Circuit Figure 8: Driver Short Circuit Current Limit Test
R
RV
OC
D
Vcc
V
OD
GENERATOR
(NOTE 1) 50Ω
CL OUT
D
V
CC
RL
54Ω
15pF
(NOTE 2)
GENERATOR
(NOTE 1) 50Ω
C
L
OUT
D
V
CC
R
L
=
60Ω
C
L
= 15pF (NOTE 2)
GENERATOR
(NOTE 1) 50Ω
S1
R
L
= 110Ω
OUT
C
L
= 50pF
(NOTE 2)
D
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)
1.5V
-1.5V
S3
V
ID
GENERATOR
(NOTE 1)
50Ω
C
L
= 15pF
(NOTE 2)
R
1k
S1
S2
V
CC
A
D
DI = 0 or Vcc
B
DE = 0 or Vcc
I
OS D
-7V to +12V V
NOTES
1: The input pulse is supplied by a generator with the following characteristics:
PRR = 250kHz, 50% duty cycle, tR < 6.0ns, ZO = 50Ω.
2: CL includes probe and stray capacitance.
SP3485
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REV 2.0.1
Switching Waveforms
Figure 9: Driver Propagation Delay Waveforms Figure 10: Driver Differential Output Delay
and Transition Time Waveforms
Figure 11: Driver Enable and Disable Timing Waveforms Figure 12: Receiver Propagation Delay Waveforms
Figure 13: Receiver Enable and Disable Waveforms
0V
VOH
tPLH tPHL
VOM
tPHL tPLH
3V
VOL
VOH
1.5V 1.5V
INPUT
Y OUTPUT
VOM
Z OUTPUT
VOL
VOM
VOM
VOM = VOH + VOL
2
≈ 1.5V
IN 1.5V
t
DO1
1.5V
t
DO2
3V
0V
OUT
50% 50%
10% 10%
90% 90%
t
TD
t
TD
2.0V
-2.0V
0V
VOH
tPZH
tPSH
0.25V
tPHZ
VOM
tPSL
tPZL
tPLZ
VOL
VCC
1.5V 1.5V
DE
HIGH
VOM
0.25V
0V
LOW
VOM = VOH + VOL
≈ 1.5V
3V
0V
VCC
tRPLH
1.5V
tRPHL
VOM VOM
0V
1.5V
INPUT
OUTPUT
VOM = VCC
2
3V
0V
tPRHZ
1.5V
tPRZH
tPRSH
1.5V
1.5V
10%
0V
VOH
RE
OUTPUT
S1 is open
S2 is closed
S3 = 1.5V
3V
0V
tPRLZ
1.5V
tPRZL
tPRSL
1.5V
1.5V
10%
VCC
RE
OUTPUT
S1 is closed
S2 is open
S3 = -1.5V
VOL
SP3485
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Description
The SP3485 is a member in the family of 3.3V low power half-
duplex transceivers that meet the electrical specifications of
the RS-485 and RS-422 serial protocols. This device is pin-
to-pin compatible with the MaxLinear SP481, SP483 and
SP485 devices as well as popular industry standards. The
SP3485 feature MaxLinear’s BiCMOS process allowing low
power operationwithout sacrificing performance.
Driver
The driver outputs of the SP3485 are differential outputs
meeting the RS-485 and RS-422 standards. The typical
voltage output swing with no load will be 0 volts to 3.3 Volts.
With a load of 54Ω across the differential outputs, the drivers
can maintain greater than 1.5V voltage levels.
The driver of the SP3485 has a driver enable control line
which is active HIGH. A logic HIGH on DE (pin 3) will enable
the differential driver outputs. A logic LOW on the DE (pin
3) will tri-state the driver outputs.
The driver of the SP3485 operates up to 10Mbps. The
250mA ISC maximum limit on the driver output allows the
SP3485 to withstand an infinite short circuit over the -7.0V
to 12V common mode range without catastrophic damage
to the IC.
Receiver
The SP3485 receiver has differential inputs with an input
sensitivity of ±200mV. Input impedance of the receiver
is 12kΩ minimum. A wide common mode range of -7V to
12V allows for large ground potential differences between
systems. The receiver is 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
SP3485 operates up to 10Mbps.
The receiver of the SP3485 has an enable control line
which is active LOW. A logic LOW on RE (pin 2) will enable
the differential receiver. A logic HIGH on RE (pin 2) of the
SP3485 will disable the receiver.
Low Power Shutdown Mode
Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the devices typically
draw only 50nA of supply current. RE and DE can be
driven simultaneously; the part is guaranteed not to enter
shutdown if RE is high and DE is low for less than 50ns. If
the inputs are in this state for at least 600ns, the parts are
guaranteed to enter shutdown.
Enable times tPRZH, tPZH, tPRZL and tPZL assume the part
was not in a low-power shutdown state. Enable times tPRSH,
tPSH, tPRSL and tPSL assume the parts were shut down. It
takes drivers and receivers longer to become enabled from
low-power shutdown mode (tPRSH, tPSH, tPRSL, tPSL) than
from driver/receiver-disable mode (tPRZH, tPZH, tPRZL, tPZL).
INPUTS OUTPUTS
RE DE DI BA
X 1 1 0 1
X 1 0 1 0
0 0 X High-Z
1 0 X Shutdown
Table 1: Transmit Function Truth Table
INPUTS OUTPUTS
RE DE VA - VBRO
0 X -50mV 1
0 X -200mV 0
X X Open/Shorted 1
1 1 X High-Z
1 0 X Shutdown
Table 2: Receive Function Truth Table
SP3485
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Mechanical Dimensions
NSOIC8
Drawing No:
Revision: A
Side View
Top View
Front View
POD-00000108
SP3485
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Company and product names may be registered trademarks or trademarks of the respective owners with which they are associated.
© 2012-2017 MaxLinear, Inc. All rights reserved
SP3485_DS_090617 9/9
REV 2.0.1
Corporate Headquarters:
5966 La Place Court
Suite 100
Carlsbad, CA 92008
Tel.:+1 (760) 692-0711
Fax: +1 (760) 444-8598
www.maxlinear.com
High Performance Analog:
48720 Kato Road
Fremont, CA 94538
Tel.: +1 (510) 668-7000
Fax: +1 (510) 668-7001
Email: serialtechsupport@exar.com
www.exar.com
Ordering Information(1)
Part Number Operating Temperature Range Lead-Free Package Packaging Method
SP3485CN-L
0°C to 70°C
Yes(2) 8-pin SOIC
Tube
SP3485CN-L/TR Reel
SP3485EN-L
-40°C to 85°C
Tube
SP3485EN-L/TR Reel
NOTE:
1. Refer to www.exar.com/SP3485 for most up-to-date Ordering Information.
2. Visit www.exar.com for additional information on Environmental Rating.
Revision History
Revision Date Description
10/15/02 -- Legacy Sipex Datasheet
06/19/12 1.0.0 Convert to Exar Format. Update ordering information and add new Figure 8 - Driver Short
Circuit Current Limit Test Circuit. Remove EOL device SP3481.
06/27/16 2.0.0
Update logo. Update description paragraph on page 1. Update timing specifications in
electrical characteristics table on pages 2 and 3. Add Driver and Receiver Enable from
Shutdown timing information on pages 3 and 4. Update typical supply current information
on page 4. Update Figures 2, 4, 6, and 8. Update Figures 11 and 13 to add shutdown timing
labels. Add low power shutdown section to page 7. Update transmit and receive truth tables
on page 7. Update Receiver section on page 7.
09/06/17 2.0.1
Remove GND from Differential Output Voltage min (page 2). Added maximum junction
temperature, package power dissipation and ESD rating. Update to MaxLinear logo, update
format and ordering information table.