LTC1480
3.3V Ultralow Power
RS485 Transceiver
FEATURES
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DESCRIPTIO
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
–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
Available in 8-Lead DIP and SO Packages
The LTC
®
1480 is an ultralow 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.
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.
All other trademarks are the property of their respective owners.
APPLICATIO S
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Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
TYPICAL APPLICATIO
3.3V
LTC1480
RO
RE
DE
DI
R
B
120Ω
A
D
SHIELD
3.3V RS485 Network
3.3V
LTC1480
SHIELD
B
120Ω
A
3.3V
B
A
D
R
RO
OUTPUT VOLTAGE (V)
RE
DE
DI
R
LTC1480
D
1480 TA01
RO
RE DE DI
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
1480 TA02
U
U
1480fa
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
T
JMAX
= 125°C,
θ
JA
= 130°C/ W (N8)
T
JMAX
= 125°C,
θ
JA
= 150°C/ W (S8)
ORDER PART NUMBER
LTC1480CN8
LTC1480IN8
LTC1480CS8
LTC1480IS8
S8 PART MARKING
1480
1480I
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
temperature range. V
CC
= 3.3V (Notes 2, 3).
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
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
The
●
denotes the specifications which apply over the full operating
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
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
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
600
500
10
0.2
1480fa
2
U
V
µA
mA
mA
V
mV
V
V
µA
kΩ
µA
µA
µA
W
U
U
W W
W
LTC1480
temperature range. V
CC
= 3.3V (Notes 2, 3).
SYMBOL
I
OSD1
I
OSD2
I
OSR
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 Short-Circuit Current, V
OUT
= HIGH
Driver Short-Circuit Current, V
OUT
= LOW
Receiver Short-Circuit Current
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
SWITCHI G CHARACTERISTICS
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
C
L
= 15pF (Figures 2, 8), S1 Closed
●
4500
ns
Note 2:
All currents into device pins are positive; all currents out ot device pins
Note 1:
Absolute maximum ratings are those beyond which the safety of
are negative. All voltages are referenced to device ground unless otherwise specified.
the device cannot be guaranteed.
Note 3:
All typicals are given for V
CC
= 3.3V and T
A
= 25°C.
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Temperature
425
150
400
SUPPLY CURRENT (µA)
OUTPUT CURRENT (mA)
375
350
325
300
275
DIFFERENTIAL VOLTAGE (V)
THERMAL SHUTDOWN
WITH DRIVER ENABLED
DRIVER DISABLED
250
225
V
CC
= 3.3V
–150
200
–50
–25
0
25 50
75
100 125 150 175
TEMPERATURE (°C)
1480 G01
U W
U
The
●
denotes the specifications which apply over the full operating
MIN
●
●
●
●
●
●
●
CONDITIONS
– 7V
≤
V
O
≤
12V
– 7V
≤
V
O
≤
12V
0V
≤
V
O
≤
V
CC
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 3, 5)
TYP
MAX
250
250
85
UNITS
mA
mA
mA
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Mbits/s
ns
ns
ns
ns
35
35
7
25
25
5
50
50
10
15
70
70
70
70
30
30
140
140
13
50
50
50
50
2.5
50
200
70
70
80
80
20
40
120
120
120
120
200
200
80
80
80
80
600
120
120
4500
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
●
●
●
●
●
●
●
●
●
Driver Output Low/High Voltage
vs Output Current
2.2
Driver Differential Output Voltage
vs Temperature
2.1
2.0
1.9
R
L
= 54Ω
1.8
1.7
1.6
V
CC
= 3.3V
1.5
–40 –20
R
L
= 100Ω
100
50
0
– 50
–100
V
CC
= 3.3V
T
A
= 25°C
0
0.5
1.0 1.5 2.0 2.5
OUTPUT VOLTAGE (V)
3.0
3.5
1480 G02
40
20
60
0
TEMPERATURE (°C)
80
100
1480 G03
1480fa
3
LTC1480
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Skew vs Temperature
7.0
V
CC
= 3.3V
6.5
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
6.0
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
8
TIME (ns)
OUTPUT VOLTAGE (V)
0.4
0.3
0.2
0.1
0
–40 –20
OUTPUT VOLTAGE (V)
6
4
2
0
–40 –20
40
20
60
0
TEMPERATURE (°C)
PI FU CTIO S
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.
1480fa
4
U W
80
1480 G04
Receiver Output Low Voltage
vs Output Current
25
V
CC
= 3.3V
T
A
= 25°C
20
– 12
– 10
–8
–6
–4
–2
0
100
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
OUTPUT VOLTAGE (V)
1480 G05
Receiver Output High Voltage
vs Output Current
– 16
– 14
V
CC
= 3.3V
T
A
= 25°C
15
10
5
0
3.30 3.05 2.80 2.55 2.30 2.05 1.80 1.55 1.30
OUTPUT VOLTAGE (V)
1480 G06
Receiver Output Low Voltage
vs Temperature
0.6
0.5
V
CC
= 3.3V
I
O
= 8mA
2.8
3.0
Receiver Output High Voltage
vs Temperature
V
CC
= 3.3V
I
O
= 8mA
2.6
2.4
2.2
80
100
1480 G07
40
20
60
0
TEMPERATURE (°C)
80
100
1480 G08
2.0
– 40 – 20
40
20
0
60
TEMPERATURE (°C)
80
100
1480 G09
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
1480 F01
3V
DE
A
DI LTC1480
DRIVER
B
R
DIFF
C
L2
C
L1
A
LTC1480
B RECEIVER
RE
1480 F03
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%
1480 F05
1.5V
f = 1MHz, t
r
≤
10ns, t
f
≤
10ns
t
PHL
Figure 5. Driver Propagation Delays
1480fa
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
1480 F02
Figure 1. Driver DC Test Load
Figure 2. Receiver Timing Test Load
S1
RO
15pF
OUTPUT
UNDER TEST
500Ω
S2
C
L
1480 F04
V
CC
Figure 4. Driver Timing Test Load
1.5V
1/2 V
O
5
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