1
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
DESCRIPTION
FEATURES
• Allows Over 400 Transceivers On A
Transmission Line (1/10th Unit Load)
• High Impedance on Receiver Inputs
(RIN = 150kΩ typical)
• Half-Duplex Conguration Consistent
With Industry Standard Pinout
• -7V to +12V Common Mode Input
Voltage Range
• Low Power Consumption (250mW)
• Separate Driver and Receiver Enable
SP485R
1/10th Unit Load RS-485 Transceiver
The SP485R is a pin-to-pin equivalent to our existing SP485 product and offers a high
receiver input impedance. The higher receiver input impedance allows for connecting over
400 transceivers on a single transmission line without degrading the RS-485 driver signal.
The device is packaged in a 8-pin plastic DIP or 8-pin narrow SOIC.
Figure 1. Typical Application Circuit
2
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
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 specications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may
affect reliability.
VCC.......................................................................+7V
Storage Temperature.......................-65˚C to +150˚C
ELECTRICAL CHARACTERISTICS
Typically 25ºC @ VCC = +5V unless otherwise noted.
PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
LOGIC INPUTS
VIL 0.8 Volts
VIH 2.0 Volts
LOGIC OUTPUTS
VOL 0.4 Volts IOUT = -3.2mA
VOH 2.4 Volts IOUT = 1.0mA
RS-485 DRIVER DC Characteristics
Open Circuit Voltage 6.0 Volts
Differential Output Voltage 1.5 5.0 Volts RL = 54Ω, CL = 50pF
Balance +/-0.2 Volts |VT| - |VT|
Common-Mode Output 3.0 Volts
Output Current 28.0 mA RL = 54Ω
Short Circuit Current +/-250 mA Terminated in -7V to +12V
RS-485 DRIVER AC Characteristics
Maximum Data Rate 5 Mbps RL = 54Ω,
Output Transition Time 30 ns Rise/fall time, 10% to 90%
Propagation Delay, tPLH 60 100 ns See Figures 4 & 6, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Propagation Delay, tPHL 60 100 ns See Figures 4 & 6, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Driver Output Skew 5 15 ns see Figures 4 and 6,
tSKEW = |tDPHL - tDPLH|
RS-485 RECEIVER DC Characteristics
Output Voltage Low, VOL 0.4 Volts
Output Voltage High, VOH 2.4 Volts
Tri-State Output Current +/-1 µA 0.4V ≤ VOUT ≤ 2.4V; RE = Vcc
Power Dissipation
8-pin NSOIC.................................................1000mW
(ØJA = 62ºC/W)
8-pin PDIP....................................................1000mW
(ØJA = 62ºC/W)
3
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
PARAMETERS MIN. TYP. MAX. UNITS CONDITIONS
RS-485 RECEIVER DC Characteristics (continued)
Common Mode Range -7.0 +12.0 Volts
Receiver Sensitivity +/-0.2 Volts -7V ≤ VCM ≤ +12V
Input Impedance 120 150 kΩ -7V ≤ VCM ≤ +12V
RS-485 RECEIVER AC Characteristics
Maximum Data Rate 1 Mbps
Propagation Delay; tPHL 1200 ns See Figures 4 & 8, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Propagation Delay; tPLH 1200 ns See Figures 4 & 8, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Differential Receiver Skew 60 ns See Figures 4 & 8, RDIFF = 54Ω,
CL1 = CL2 = 100pF,
tSKEW = |tPHL - tPLH|
RS-485 DRIVER Enable / Disable Time
Driver Enable to Output Low 40 500 ns CL = 15pF, see Figures 5 and 7,
S1 closed
Driver Enable to Output High 40 500 ns CL = 15pF, see Figures 5 and 7,
S2 closed
Driver Disable Time from Low 40 500 ns CL = 15pF, see Figures 5 and 7,
S1 closed
Driver Disable Time from High 40 500 ns CL = 15pF, see Figures 5 and 7,
S2 closed
RS-485 RECEIVER Enable / Disable Time
Receiver Enable to Output Low 40 500 ns CL = 15pF, see Figures 3 and 9,
S1 closed
Receiver Enable to Output High 40 500 ns CL = 15pF, see Figures 3 and 9,
S2 closed
Receiver Disable from Low 40 500 ns CL = 15pF, see Figures 3 and 9,
S1 closed
Receiver Disable from High 40 500 ns CL = 15pF, see Figures 3 and 9,
S1 closed
POWER REQUIREMENTS
Supply Voltage VCC +4.75 +5.25 Volts
Supply Current ICC, No Load 300 500 µA RE = Vcc or 0V, DE = 0V
Supply Current ICC, No Load 500 900 µA RE = Vcc or 0V, DE = Vcc
ENVIRONMENTAL
Operating Temperature
Commercial (..C..) 0 +70 ºC
Industrial (..E..) -40 +85 ºC
Storage Temperature -65 +150 ºC
ELECTRICAL CHARACTERISTICS
Typically 25ºC @ VCC = +5V unless otherwise noted.
4
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
PIN FUNCTION
TEST CIRCUITS
A
B
R
R
V
OD
V
OC
Figure 2. Driver DC Test Load Circuit
CL1
15pF
RO
A
B
A
B
DI
CL2
RL
Figure 4. RS-485 Driver/Receiver Timing Test
500Ω
CL
Output
Under
Test
S1
S2
VCC
Figure 5. Driver Timing Test Load #2 Circuit
Figure 3. Receiver Timing Test Load Circuit
1kΩ
1kΩCRL
Receiver
Output S1
S2
Test Point
VCC
Pin 1 - RO - Receiver Output
Pin 2 - RE - Receiver Output Enable Active LOW
Pin 3 - DE - Driver Output Enable Active HIGH
Pin 4 DI - Driver Input
Pin 5 - GND - Ground Connection
Pin 6 - A - Driver Output / Receiver input
Non-Inverting
Pin 7 - B - Driver Output / Receiver Input Inverting
Pin 8 - Vcc - Positive Supply 4.75V ≤ Vcc ≤ 5.25V
RECEIVER INPUT GRAPH
-7V -3V
+6V +12V
-0.6mA
+1.0mA
1 Unit Load
Maximum Input Current
versus voltage.
(Shaded region)
Standard SP485 Reciever
-7V -3V
+6V +12V
-60µA
+100µA
1/10 Unit Load
Maximum Input Current
versus voltage.
(Shaded region)
SP485R Reciever
5
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
Figure 6. Driver Propagation Delays
+3V
0V
DRIVER INPUT
A
B
DRIVER
OUTPUT
V
O
+
DIFFERENTIAL
OUTPUT
V
A
– V
B
0V
V
O
–
1.5V 1.5V
t
PLH
t
F
t
R
f ≥ 1MHz; t
R
≤ 10ns; t
F
≤ 10ns
V
O
1/2V
O
1/2V
O
t
PHL
t
SKEW
= |t
DPLH
- t
DPHL
|
t
DPLH
t
DPHL
Figure 7. Driver Enable and Disable Times
Figure 9. Receiver Enable and Disable Times
+3V
0V
DE
5V
VOL
A
, B
0V
1.5V 1.5V
tZL
tZH
f = 1MHz; tR
< 10ns; tF < 10ns
VOH
A
, B 2.3V
2.3V
tLZ
tHZ
0.5V
0.5V
Output normally LOW
Output normally HIGH
V
OH
V
OL
RECEIVER OUT 1.5V 1.5V
t
PHL
f = 1MHz; t
R
10ns; t
F
≤ 10ns
OUTPUT
V
OD2
+
V
OD2
–
A – B 0V 0V
t
PLH
INPUT
≤
+3V
0V
5V
0V
1.5V 1.5V
t
ZL
t
ZH
f = 1MHz; t
R
≤ 10ns; t
F
≤ 10ns
RECEIVER OUT 1.5V
1.5V
t
LZ
t
HZ
0.5V
0.5V
Output normally LOW
Output normally HIGH
V
IL
V
IH
RE
RECEIVER OUT
Figure 8. Receiver Propagation Delays
SWITCHING WAVEFORMS
6
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
The SP485R is a low power RS-485 dif-
ferential transceiver. Similar to the SP485,
the SP485R contains a half-duplex driver
and receiver with tri-state control. However,
the SP485R is intended for increased con-
nections on a single bus compared to the
original RS-485 specifcation.
The RS-485 standard is ideal for multi-drop
applications where one bus can contain
many drivers and/or receivers.The RS-485
standard implementation allows up to 32
transceivers to be connected on to the data
bus. RS-485 is also specied for driving
higher speeds over long cable lengths of
up to 4000 feet. The SP485R exceeds the
standard by allowing up to 400 receivers to
share the bus
DRIVERS
The driver output complies with the RS-
485 electrical characteristics as specied
by the standard. The output swings from
0V to Vcc and maintains greater than +1.5V
with a 54Ω load attached between the two
outputs. In adhering to the RS-485 speci-
cation, the driver outputs inherently comply
with the RS-422 standard. With a load of
100Ω between the two outputs, the driver
can sustain at least +2.0V.
The driver contains an enable pin (DE) which
tri-states the output when DE is logic LOW.
The outputs during the tri-state condition are
at high impedance (>100kΩ). A logic HIGH
enables the driver for normal operation. The
driver can operate to at least 5Mbps.
RECEIVERS
The SP485R receiver has differential in-
puts with an input sensitivity of lower than
±200mV. As mentioned above, the RS-485
specication allows up to 32 transceivers on
the same bus. The SP485R allows over 400
transceivers on the same bus due to its high
impedance of at least 120kΩ. This higher
capacity allows more components to be at-
tached to the same bus without degrading
the signal quality. The drivers are still able to
drive an equivalent 54Ω from the 320
transceivers with an input impedance of at
least 120kΩ in parallel along with the two
125Ω cable termination resistors on each
end.
The receiver contains an enable pin (RE)
which enables the receiver when a logic LOW
is asserted. A logic HIGH will tri-state the
receiver output and the inputs will maintain
at least 120kΩ impedance. The reciever can
operate to at least 1Mbps
The receiver also contains a fail-safe
feature which outputs a logic HIGH when
the inputs are open as in a disconnected
cable.
DESCRIPTION
7
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
8
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
9
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP485R_100_072309
ORDERING INFORMATION
Model Temperature Range Package Types
SP485RCN-L ....................................................................... 0°C to +70°C ................................................................................................8-pin NSOIC
SP485RCN-L/TR ................................................................. 0°C to +70°C ................................................................................................8-pin NSOIC
SP485RCP-L....................................................................... 0°C to +70°C................................................................................................8-pin PDIP
SP485REN-L...................................................................... -40°C to +85°C..............................................................................................8-pin NSOIC
SP485REN-L/TR................................................................ -40°C to +85°C..............................................................................................8-pin NSOIC
SP485REP-L...................................................................... -40°C to +85°C..............................................................................................8-pin PDIP
REVISION HISTORy
DATE REVISION DESCRIPTION
06/21/04 -- Legacy Sipex Datasheet
07/23/09 1.0.0 Convert to Exar Format. Update ordering information as a result of discontinued
Lead type package options per PDN 081126-01. Remove all reference to the dis-
continued SP481R.
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 specic 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 signicantly 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 2009 EXAR Corporation
Datasheet July 2009
Send your Interface technical inquiry with technical details to: uarttechsupport@exar.com
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
Note: /TR = Tape and Reel