LTC1481
Ultralow Power
RS485 Transceiver
with Shutdown
FEATURES
s
s
s
s
s
s
s
DESCRIPTIO
s
s
s
s
s
s
Low Power: I
CC
= 120µA Max with Driver Disabled
Drivers/Receivers Have
±10kV
ESD Protection
1µA Quiescent Current in Shutdown Mode
High Speed: Up to 2.5Mbits/s Data Rate
I
CC
= 500µA Max with Driver Enabled, No Load
Single 5V Supply
– 7V to 12V Common Mode Range Permits
±7V
Ground Difference Between Devices on the Data Line
Thermal Shutdown Protection
Power Up/Down Glitch-Free Driver Outputs Permit
Live Insertion or Removal of Transceiver
Driver Maintains High Impedance in Three-State
or with the Power Off
Up to 32 Transceivers on the Bus
30ns Typical Driver Propagation Delays
with 5ns Skew
Pin Compatible with the LTC485
The LTC
®
1481 is an ultralow power differential line trans-
ceiver designed for data transmission standard RS485
applications. It will also meet the requirements of RS422.
The CMOS design offers significant power savings over its
bipolar counterparts without sacrificing ruggedness against
overload or ESD damage. Typical quiescent current is only
80µA while operating and less than 1µA in shutdown.
The driver and receiver feature three-state outputs, with
the driver outputs maintaining high impedance over the
entire common mode range. Excessive power dissipation
caused by bus contention or faults is prevented by a
thermal shutdown circuit which forces the driver outputs
into a high impedance state. The receiver has a fail-safe
feature which guarantees a high output state when the
inputs are left open.
The LTC1481 is fully specified over the commercial and
extended industrial temperature range and is available in
8-pin PDIP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
TYPICAL APPLICATIO
RO1
RE1
DE1
DI1
D
R
V
CC1
Supply Current vs Temperature
350
300
SUPPLY CURRENT (µA)
Rt
250
DRIVER ENABLED
200
150
100
50
DRIVER DISABLED
THERMAL SHUTDOWN
WITH DRIVER ENABLED
GND1
Rt
RO2
RE2
DE2
DI2
D
GND2
LTC1481 • TA01
R
V
CC2
0
–50 –25
U
0
25 50 75 100 125 150 175
TEMPERATURE (°C)
1481 TA02
U
U
1481fa
1
LTC1481
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RO 1
RE 2
DE 3
DI 4
N8 PACKAGE
8-LEAD PDIP
D
R
8
7
6
5
V
CC
B
A
GND
Supply Voltage (V
CC
) .............................................. 12V
Control Input Voltage ..................... – 0.5V to V
CC
+ 0.5V
Driver Input Voltage ....................... – 0.5V to V
CC
+ 0.5V
Driver Output Voltage ...........................................
±14V
Receiver Input Voltage ..........................................
±14V
Receiver Output Voltage ................ – 0.5V to V
CC
+ 0.5V
Operating Temperature Range
LTC1481C ....................................... 0°C
≤
T
A
≤
70°C
LTC1481I .................................... – 40°C
≤
T
A
≤
85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1481CN8
LTC1481IN8
LTC1481CS8
LTC1481IS8
S8 PART MARKING
1481
1481I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 130°C/ W (N8)
T
JMAX
= 125°C,
θ
JA
= 150°C/ W (S8)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
OD1
V
OD2
∆V
OD
V
OC
∆
V
OC
V
IH
V
IL
I
IN1
I
IN2
V
TH
∆V
TH
V
OH
V
OL
I
OZR
R
IN
I
CC
I
SHDN
I
OSD1
I
OSD2
I
OSR
PARAMETER
Differential Driver Output Voltage (Unloaded)
Differential Driver Output Voltage (with Load)
Change in Magnitude of Driver Differential Output
Voltage for Complementary Output States
Driver Common Mode Output Voltage
Change in Magnitude of Driver Common Mode
Output Voltage for Complementary Output States
Input High Voltage
Input Low Voltage
Input Current
Input Current (A, B)
Differential Input Threshold Voltage for Receiver
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
Three-State (High Impedance) Output
Current at Receiver
Receiver Input Resistance
Supply Current
Supply Current in Shutdown Mode
Driver Short-Circuit Current, V
OUT
= HIGH
Driver Short-Circuit Current, V
OUT
= LOW
Receiver Short-Circuit Current
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V (Notes 2, 3) unless otherwise noted.
CONDITIONS
I
O
= 0
R = 50Ω (RS422)
R = 27Ω (RS485), Figure 1
R = 27Ω or R = 50Ω, Figure 1
R = 27Ω or R = 50Ω, Figure 1
R = 27Ω or R = 50Ω, Figure 1
DE, DI, RE
DE, DI, RE
DE, DI, RE
DE = 0, V
CC
= 0V or 5.25V, V
IN
= 12V
DE = 0, V
CC
= 0V or 5.25V, V
IN
= – 7V
– 7V
≤
V
CM
≤
12V
V
CM
= 0V
I
O
= – 4mA, V
ID
= 200mV
I
O
= 4mA, V
ID
= – 200mV
V
CC
= Max, 0.4V
≤
V
O
≤
2.4V
– 7V
≤
V
CM
≤
12V
No Load, Output Enabled
No Load, Output Disabled
DE = 0, RE = V
CC
– 7V
≤
V
O
≤
12V
– 7V
≤
V
O
≤
12V
0V
≤
V
O
≤
V
CC
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
MIN
2.0
1.5
TYP
MAX
5
5
0.2
3
0.2
UNITS
V
V
V
V
V
V
V
2
0.8
±2
1.0
– 0.8
– 0.2
45
3.5
0.4
±1
12
300
80
1
35
35
7
500
120
10
250
250
85
0.2
2
U
V
µA
mA
mA
V
mV
V
V
µA
kΩ
µA
µA
µA
mA
mA
mA
1481fa
W
U
U
W W
W
LTC1481
SWITCHI G CHARACTERISTICS
SYMBOL
t
PLH
t
PHL
t
SKEW
t
r
, t
f
t
ZH
t
ZL
t
LZ
t
HZ
t
PLH
t
PHL
t
SKD
t
ZL
t
ZH
t
LZ
t
HZ
f
MAX
t
SHDN
t
ZH(SHDN)
t
ZL(SHDN)
t
ZH(SHDN)
t
ZL(SHDN)
PARAMETER
Driver Input to Output
Driver Input to Output
Driver Output to Output
Driver Rise or Fall Time
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
Receiver Input to Output
Receiver Input to Output
t
PLH
– t
PHL
Differential Receiver Skew
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V (Notes 2, 3) unless otherwise noted.
CONDITIONS
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 3, 5)
q
q
q
q
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable from Low
Receiver Disable from High
Maximum Data Rate
Time to Shutdown
Driver Enable from Shutdown to Output High
Driver Enable from Shutdown to Output Low
Receiver Enable from Shutdown to Output High
Receiver Enable from Shutdown to Output Low
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to device ground unless
otherwise specified.
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Differential Output Voltage
vs Output Current
70
60
DIFFERENTIAL VOLTAGE (V)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
50
40
30
20
10
0
0
1
4
3
OUTPUT VOLTAGE (V)
2
5
1481 G01
U W
U
MIN
10
10
3
TYP
30
30
5
15
40
40
40
40
MAX
60
60
10
40
70
70
70
70
200
200
50
50
50
50
600
100
100
3500
3500
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Mbits/s
ns
ns
ns
ns
ns
C
L
= 100pF (Figures 4, 6), S2 Closed
C
L
= 100pF (Figures 4, 6), S1 Closed
C
L
= 15pF (Figures 4, 6), S1 Closed
C
L
= 15pF (Figures 4, 6), S2 Closed
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 3, 7)
C
RL
= 15pF (Figures 2, 8), S1 Closed
C
RL
= 15pF (Figures 2, 8), S2 Closed
C
RL
= 15pF (Figures 2, 8), S1 Closed
C
RL
= 15pF (Figures 2, 8), S2 Closed
DE = 0, RE =
C
L
= 100pF (Figures 4, 6), S2 Closed
C
L
= 100pF (Figures 4, 6), S1 Closed
C
L
= 15pF (Figures 2, 8), S2 Closed
C
L
= 15pF (Figures 2, 8), S1 Closed
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
30
30
140
140
13
20
20
20
20
2.5
50
200
40
40
Note 3:
All typicals are given for V
CC
= 5V and T
A
= 25°C.
Driver Differential Output Voltage
vs Temperature
2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
–50 –25
50
0
75
25
TEMPERATURE (°C)
100
125
10
0
Driver Output Low Voltage
vs Output Current
70
60
50
40
30
20
T
A
= 25°C
T
A
= 25°C
R
L
= 54Ω
0
1
2
OUTPUT VOLTAGE (V)
3
4
1481 G03
1481 G02
1481fa
3
LTC1481
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output High Voltage
vs Output Current
0
–10
OUTPUT CURRENT (mA)
T
A
= 25°C
–20
–30
TIME (ns)
–40
–50
–60
8
6
4
TIME (ns)
–70
–80
–90
0
1
2
3
OUTPUT VOLTAGE (V)
4
5
1481 G04
PI FU CTIO S
RO (Pin 1):
Receiver Output. If the receiver output is
enabled (RE low), then if A > B by 200mV, RO will be high.
If A < B by 200mV, then RO will be low.
RE (Pin 2):
Receiver Output Enable. A low enables the
receiver output, RO. A high input forces the receiver
output into a high impedance state.
DE (Pin 3):
Driver Outputs Enable. A high on DE enables
the driver output. A, B and the chip will function as a line
driver. A low input will force the driver outputs into a high
impedance state and the chip will function as a line
receiver. If RE is high and DE is low, the part will enter a low
power (1µA) shutdown state.
DI (Pin 4):
Driver Input. If the driver outputs are enabled
(DE high) then a low on DI forces the outputs A low and B
high. A high on DI with the driver outputs enabled will force
A high and B low.
GND (Pin 5):
Ground.
A (Pin 6):
Driver Output/Receiver Input.
B (Pin 7):
Driver Output/Receiver Input.
V
CC
(Pin 8):
Positive Supply. 4.75V < V
CC
< 5.25V.
FU CTIO TABLES
LTC1481 Transmitting
INPUTS
RE
X
X
0
1
DE
1
1
0
0
DI
1
0
X
X
0
1
Z
Z*
OUTPUTS
B
A
1
0
Z
Z*
RE
0
0
0
1
*Shutdown mode for LTC1481
4
U W
Receiver
t
PLH
– t
PHL
vs
Temperature
14
12
10
3.0
2.5
2.0
1.5
1.0
0.5
Driver Skew vs Temperature
2
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1481 G05
1481 G05
U
U
U
U
U
LTC1481 Receiving
INPUTS
DE
0
0
0
0
A–B
≥
0.2V
≤
– 0.2V
Inputs Open
X
OUTPUTS
RO
1
0
1
Z*
*Shutdown mode for LTC1481
1481fa
LTC1481
TEST CIRCUITS
A
R
V
OD
R
B
LTC1481 • F01
RECEIVER
OUTPUT
V
OC
TEST POINT
S1
1k
V
CC
C
RL
1k
S2
LTC1481 • F02
Figure 1. Driver DC Test Load
3V
DE
A
DI
B
R
DIFF
C
L2
C
L1
A
RO
B
RE
LTC1481 • F03
Figure 2. Receiver Timing Test Load
S1
OUTPUT
UNDER TEST
500Ω
S2
C
L
LTC1481 • F04
V
CC
15pF
Figure 3. Driver/Receiver Timing Test Circuit
Figure 4. Driver Timing Test Load
SWITCHI G TI E WAVEFOR S
3V
DI
0V
t
PLH
B
V
O
A
V
O
0V
–V
O
1/2 V
O
10%
t
r
t
SKEW
90%
V
DIFF
= V(A) – V(B)
t
f
t
SKEW
90%
10%
LTC1481 • F05
1.5V
Figure 5. Driver Propagation Delays
3V
DE
0V
5V
A, B
V
OL
V
OH
A, B
0V
2.3V
1.5V
Figure 6. Driver Enable and Disable Times
1481fa
W
W
U
f = 1MHz, t
r
≤
10ns, t
f
≤
10ns
t
PHL
1.5V
1/2 V
O
f = 1MHz, t
r
≤
10ns, t
f
≤
10ns
t
ZL(SHDN)
, t
ZL
t
LZ
1.5V
2.3V
OUTPUT NORMALLY LOW
0.5V
OUTPUT NORMALLY HIGH
t
HZ
0.5V
LTC1481 • F06
t
ZH(SHDN)
, t
ZH
5
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