SP485R
1/10th Unit Load RS-485 Transceiver
FEATURES
• Allows Over 400 Transceivers On A
Transmission Line (/0th Unit Load)
• High Impedance on Receiver Inputs
(R
IN
= 150kΩ typical)
• Half-Duplex Configuration Consistent
With Industry Standard Pinout
• -7V to +2V Common Mode Input
Voltage Range
• Low Power Consumption (250mW)
• Separate Driver and Receiver Enable
DESCRIPTION
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
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com
SP485R_00_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 specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may
affect reliability.
V
CC
.......................................................................+7V
Storage Temperature.......................-65˚C to +150˚C
Typically 25ºC @ V
CC
= +5V unless otherwise noted.
Power Dissipation
8-pin NSOIC.................................................000mW
(Ø
JA
= 62ºC/W)
8-pin PDIP....................................................000mW
(Ø
JA
= 62ºC/W)
ELECTRICAL CHARACTERISTICS
TYP.
MAX.
0.8
UNITS
Volts
Volts
0.4
Volts
Volts
6.0
Volts
Volts
Volts
Volts
mA
+/-250
mA
Mbps
30
60
60
5
00
00
5
ns
ns
ns
ns
R
L
= 54Ω
Terminated in -7V to +2V
R
L
= 54Ω,
Rise/fall time, 0% to 90%
See Figures 4 & 6, R
DIFF
= 54Ω,
C
L
= C
L2
= 00pF
See Figures 4 & 6, R
DIFF
= 54Ω,
C
L
= C
L2
= 00pF
see Figures 4 and 6,
t
SKEW
= |t
DPHL
- t
DPLH
|
R
L
= 54Ω, C
L
= 50pF
|V
T
| - |V
T
|
I
OUT
= -3.2mA
I
OUT
= .0mA
CONDITIONS
PARAMETERS
LOGIC INPUTS
V
IL
V
IH
LOGIC OUTPUTS
V
OL
V
OH
Open Circuit Voltage
Differential Output Voltage
Balance
Common-Mode Output
Output Current
Short Circuit Current
MIN.
2.0
2.4
RS-485 DRIVER DC Characteristics
.5
5.0
+/-0.2
3.0
28.0
RS-485 DRIVER AC Characteristics
Maximum Data Rate
Output Transition Time
Propagation Delay, t
PLH
Propagation Delay, t
PHL
Driver Output Skew
RS-485 RECEIVER DC Characteristics
Output Voltage Low, V
OL
Output Voltage High, V
OH
Tri-State Output Current
2.4
+/-
0.4
Volts
Volts
µA
0.4V ≤ V
OUT
≤ 2.4V; RE = Vcc
5
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com
SP485R_00_072309
2
Typically 25ºC @ V
CC
= +5V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
TYP.
MAX.
+2.0
+/-0.2
UNITS
Volts
Volts
kΩ
-7V ≤ V
CM
≤ +12V
-7V ≤ V
CM
≤ +12V
CONDITIONS
PARAMETERS
Common Mode Range
Receiver Sensitivity
Input Impedance
MIN.
-7.0
RS-485 RECEIVER DC Characteristics (continued)
20
50
RS-485 RECEIVER AC Characteristics
Maximum Data Rate
Propagation Delay; t
PHL
Propagation Delay; t
PLH
Differential Receiver Skew
60
200
200
Mbps
ns
ns
ns
See Figures 4 & 8, R
DIFF
= 54Ω,
C
L
= C
L2
= 00pF
See Figures 4 & 8, R
DIFF
= 54Ω,
C
L
= C
L2
= 00pF
See Figures 4 & 8, R
DIFF
= 54Ω,
C
L
= C
L2
= 00pF,
t
SKEW
= |t
PHL
- t
PLH
|
C
L
= 5pF, see Figures 5 and 7,
S
closed
C
L
= 5pF, see Figures 5 and 7,
S
2
closed
C
L
= 5pF, see Figures 5 and 7,
S
closed
C
L
= 5pF, see Figures 5 and 7,
S
2
closed
C
L
= 5pF, see Figures 3 and 9,
S
closed
C
L
= 5pF, see Figures 3 and 9,
S
2
closed
C
L
= 5pF, see Figures 3 and 9,
S
closed
C
L
= 5pF, see Figures 3 and 9,
S
closed
RS-485 DRIVER Enable / Disable Time
Driver Enable to Output Low
Driver Enable to Output High
Driver Disable Time from Low
Driver Disable Time from High
RS-485 RECEIVER Enable / Disable Time
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable from Low
Receiver Disable from High
POWER REQUIREMENTS
Supply Voltage V
CC
Supply Current I
CC
, No Load
Supply Current I
CC
, No Load
ENVIRONMENTAL
Operating Temperature
Commercial (..C..)
Industrial (..E..)
Storage Temperature
0
-40
-65
+70
+85
+50
ºC
ºC
ºC
+4.75
300
500
+5.25
500
900
Volts
µA
µA
RE = Vcc or 0V, DE = 0V
RE = Vcc or 0V, DE = Vcc
40
40
40
40
500
500
500
500
ns
ns
ns
ns
40
40
40
40
500
500
500
500
ns
ns
ns
ns
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com
SP485R_00_072309
3
PIN FUNCTION
Pin - 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
Standard SP485 Reciever
+1.0mA
SP485R Reciever
+100µA
-7V
-3V
+6V
+12V
-7V
-3V
+6V
+12V
-0.6mA
1 Unit Load
Maximum Input Current
versus voltage.
(Shaded region)
-60µA
1/10 Unit Load
Maximum Input Current
versus voltage.
(Shaded region)
TEST CIRCUITS
A
R
V
OD
R
B
Figure 2. Driver DC Test Load Circuit
Receiver
Output
V
OC
Test Point
S
1
C
RL
1kΩ
S
2
1kΩ
V
CC
Figure 3. Receiver Timing Test Load Circuit
DI
A
B
C
L1
R
L
C
L2
A
B
RO
15pF
Output
Under
Test
500Ω
C
L
S
1
V
CC
S
2
Figure 4. RS-485 Driver/Receiver Timing Test
Figure 5. Driver Timing Test Load #2 Circuit
SP485R_00_072309
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com
4
SWITCHING WAVEFORMS
+3V
0V
B
A
V
O
1/2V
O
t
DPLH
t
DPHL
f ≥ 1MHz; t
R
≤ 10ns; t
F
≤ 10ns
1.5V
t
PLH
t
PHL
1/2V
O
1.5V
DRIVER INPUT
DRIVER
OUTPUT
DIFFERENTIAL V
O
+
0V
OUTPUT
V
A
– V
B
V
O
–
t
SKEW
= |t
DPLH
- t
DPHL
|
t
R
t
F
Figure 6. Driver Propagation Delays
DE
+3V
0V
5V
V
OL
V
OH
0V
f = 1MHz; t
R
< 10ns; t
F
< 10ns
1.5V
t
ZL
2.3V
Output normally LOW
Output normally HIGH
1.5V
t
LZ
0.5V
0.5V
t
HZ
A,
B
A,
B
2.3V
t
ZH
Figure 7. Driver Enable and Disable Times
A– B
V
OD2
+
V
OD2
–
V
OH
V
OL
t
PHL
f = 1MHz; t
R
≤ 10ns ; t
F
≤ 10ns
0V
INPUT
0V
RECEIVER OUT
1.5V
OUTPUT
t
PLH
1.5V
Figure 8. Receiver Propagation Delays
RE
+3V
0V
5V
V
IL
V
IH
1.5V f = 1MHz; t ≤ 10ns; t ≤ 10ns
R
F
t
ZL
1.5V
Output normally LOW
Output normally HIGH
1.5V
t
LZ
0.5V
0.5V
t
HZ
RECEIVER OUT
RECEIVER OUT
0V
1.5V
t
ZH
Figure 9. Receiver Enable and Disable Times
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com
SP485R_00_072309
5
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