LTC1480
3.3V Ultra-Low Power
RS485 Transceiver
FEATURES
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DESCRIPTIO
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True RS485 from a Single 3.3V Supply
Low Power: I
CC
= 500µA Max with Driver Disabled
I
CC
= 600
µ
A Max with Driver Enabled, No Load
1
µ
A Quiescent in Shutdown Mode
ESD Protection to
±
10kV on Receiver Inputs and
Driver Outputs
–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
50ns Typical Driver Propagation Delays with
10ns Skew
Pin Compatible with the LTC485
The LTC
®
1480 is an ultra-low power differential line trans-
ceiver which provides full RS485 compatibility while oper-
ating from a single 3.3V supply. It is designed for data
transmission standard RS485 applications with extended
common-mode range (12V to –7V). It also meets the
requirements of RS422 and features high speed operation
up to 2.5Mb/s. The CMOS design offers significant power
savings without sacrificing ruggedness against overload
or ESD damage. Typical quiescent current is only 300µA
while operating and 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. I/O pins are protected against multiple
ESD strikes of up to
±10kV.
The LTC1480 is fully specified over the commercial and
extended industrial temperature range. The LTC1480 is
available in 8-pin SO and DIP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
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Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
TYPICAL APPLICATI
3.3V
LTC1480
RO 1
RE
DE
D1
2
3
4
D
R
8
7
6
5
B
120Ω
A
3.3V RS485 Network
3.3V
LTC1480
SHIELD
SHIELD
B
120Ω
A
3.3V
8
B
7
A
6
5
6
5
D
3
4
8
7
R
1 RO
OUTPUT VOLTAGE (V)
2
RE
DE
D1
R
1
RO
2
RE
3
LTC1480
D
4
DE D1
LTC1480 • TA01
U
Driver Differential
Output Voltage vs Output Current
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
10
20 30 40 50 60 70
OUTPUT CURRENT (mA)
80
90
V
CC
= 3.3V
T
A
= 25°C
LTC1480 • TA02
UO
UO
1
LTC1480
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
) ................................................ 7V
Control Input Voltage ..................... – 0.3V to V
CC
+ 0.3V
Driver Input Voltage ....................... – 0.3V to V
CC
+ 0.3V
Driver Output Voltage ...........................................
±14V
Receiver Input Voltage ..........................................
±14V
Receiver Output Voltage ................ – 0.3V to V
CC
+ 0.3V
Operating Temperature Range
LTC1480C........................................ 0°C
≤
T
A
≤
70°C
LTC1480I .................................... – 40°C
≤
T
A
≤
85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
S8 PACKAGE
8-LEAD PLASTIC SO
ORDER PART
NUMBER
LTC1480CN8
LTC1480IN8
LTC1480CS8
LTC1480IS8
S8 PART MARKING
1480
1480I
T
JMAX
= 125°C,
θ
JA
= 130°C/ W (N8)
T
JMAX
= 125°C,
θ
JA
= 150°C/ W (S8)
Consult factory for Military grade parts.
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
V
CC
= 3.3V (Notes 2, 3)
CONDITIONS
I
O
= 0V
R = 27Ω (RS485), Figure 1
R = 50Ω (RS422)
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 3.6V, V
IN
= 12V
DE = 0, V
CC
= 0V or 3.6V, 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
MIN
1.5
2.0
TYP
MAX
3.3
3.3
0.2
2
0.2
UNITS
V
V
V
V
V
V
V
2
0.8
±2
1.0
– 0.8
– 0.2
70
2
0.4
±1
12
400
300
1
35
35
7
600
500
10
250
250
85
0.2
2
U
V
µA
mA
mA
V
mV
V
V
µA
kΩ
µA
µA
µA
mA
mA
mA
W
U
U
W W
W
LTC1480
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
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
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute maximum ratings are those beyond which the safety of
the device cannot be guaranteed.
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
425
400
SUPPLY CURRENT (µA)
OUTPUT CURRENT (mA)
375
350
325
300
275
250
225
V
CC
= 3.3V
DIFFERENTIAL VOLTAGE (V)
THERMAL SHUTDOWN
WITH DRIVER ENABLED
DRIVER DISABLED
200
–50 –25
0
25 50 75 100 125 150 175
TEMPERATURE (°C)
LT1480 • TPC01
U W
U
V
CC
= 3.3V (Notes 2, 3)
MIN
q
q
q
q
CONDITIONS
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 3 and 5)
TYP
50
50
10
15
70
70
70
70
MAX
80
80
20
40
120
120
120
120
200
200
80
80
80
80
600
120
120
4500
4500
UNITS
ns
25
25
5
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,
(Figure 3, 7)
q
q
q
q
q
q
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Mbits/s
ns
ns
ns
ns
ns
30
30
140
140
13
50
50
50
50
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
2.5
50
200
70
70
Note 2:
All currents into device pins are positive; all currents out ot device
pins are negative. All voltages are referenced to device ground unless
otherwise specified.
Note 3:
All typicals are given for V
CC
= 3.3V and T
A
= 25°C.
Driver Output Low/High Voltage
vs Output Current
150
100
50
0
– 50
–100
–150
0
0.5
2.5
1.0 1.5 2.0
OUTPUT VOLTAGE (V)
3.0
3.5
V
CC
= 3.3V
T
A
= 25°C
2.2
2.1
2.0
1.9
Driver Differential Output Voltage
vs Temperature
R
L
= 100Ω
R
L
= 54Ω
1.8
1.7
1.6
V
CC
= 3.3V
1.5
–40 –20
40
20
60
0
TEMPERATURE (°C)
80
100
LT1480 • TPC02
LTC1480
• TPC03
3
LTC1480
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Skew vs Temperature
7.0
6.5
6.0
V
CC
= 3.3V
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
TIME (ns)
5.5
5.0
4.5
4.0
3.5
3.0
– 40 – 20
0
40
60
20
TEMPERATURE (°C)
Receiver
t
PLH
– t
PHL
vs Temperature
12
V
CC
= 3.3V
10
OUTPUT VOLTAGE (V)
8
0.4
0.3
0.2
0.1
0
–40 –20
OUTPUT VOLTAGE (V)
TIME (ns)
6
4
2
0
–40 –20
40
20
60
0
TEMPERATURE (°C)
PIN FUNCTIONS
RO (Pin 1):
Receiver Output. If the receiver output is
enabled (RE LOW) and A > B by 200mV, then 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. If RE is low and DE is
high, the driver outputs will be fed back to the receiver and
the receive output will correspond to the driver input.
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. 3.0V < V
CC
< 3.6V.
4
U W
80
LT1480 • TPC04
Receiver Output Low Voltage
vs Output Current
25
V
CC
= 3.3V
T
A
= 25°C
– 16
– 14
– 12
– 10
–8
–6
–4
–2
0
100
Receiver Output High Voltage
vs Output Current
V
CC
= 3.3V
T
A
= 25°C
20
15
10
5
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
OUTPUT VOLTAGE (V)
LTC1480 • TPC05
0
3.30 3.05 2.80 2.55 2.30 2.05 1.80 1.55 1.30
OUTPUT VOLTAGE (V)
LT1480 • TPC06
Receiver Output Low Voltage
vs Temperature
0.6
0.5
V
CC
= 3.3V
1 = 8mA
3.0
Receiver Output High Voltage
vs Temperature
V
CC
= 3.3V
1 = 8mA
2.8
2.6
2.4
2.2
80
100
40
20
60
0
TEMPERATURE (°C)
80
100
2.0
– 40 – 20
40
20
60
0
TEMPERATURE (°C)
80
100
LT1480 • TPC07
LTC1480 • TPC08
LTC1480 • TPC09
U
U
U
LTC1480
FU CTIO TABLES
LTC1480 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
TEST CIRCUITS
A
R
V
OD
R
B
LTC1480 • F01
3V
DE
A
DI LTC1480
DRIVER
B
R
DIFF
C
L2
C
L1
A
S1
Figure 3. Driver/Receiver Timing Test Circuit
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%
LTC1480 • F05
1.5V
Figure 5. Driver Propagation Delays
W
W
U
U
U
LTC1480 Receiving
INPUTS
DE
0
0
0
0
A–B
≥
0.2V
≤
– 0.2V
Inputs Open
X
OUTPUTS
RO
1
0
1
Z*
*Shutdown mode
RECEIVER
OUTPUT
V
OC
TEST POINT
S1
1k
V
CC
C
RL
1k
S2
LTC1480 • F02
Figure 1. Driver DC Test Load
Figure 2. Receiver Timing Test Load
LTC1480
B RECEIVER
RE
LTC1480 • F03
RO
15pF
OUTPUT
UNDER TEST
500Ω
S2
C
L
LTC1480 • F04
V
CC
Figure 4. Driver Timing Test Load
f = 1MHz, t
r
≤
10ns, t
f
≤
10ns
t
PHL
1.5V
1/2 V
O
5
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