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1
LTC1480
3.3V Ultra-Low Power
RS485 Transceiver
S
FEATURE
D
U
ESCRIPTIO
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 300
A
while operating and 1
A 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.
s
True RS485 from a Single 3.3V Supply
s
Low Power: I
CC
= 500
A Max with Driver Disabled
s
I
CC
= 600
A Max with Driver Enabled, No Load
s
1
A Quiescent in Shutdown Mode
s
ESD Protection to
10kV on Receiver Inputs and
Driver Outputs
s
7V to 12V Common-Mode Range Permits
7V
Ground Difference Between Devices on the Data Line
s
Thermal Shutdown Protection
s
Power Up/Down Glitch-Free Driver Outputs Permit
Live Insertion or Removal of Transceiver
s
Driver Maintains High Impedance in Three-State or
with the Power Off
s
Up to 32 Transceivers on the Bus
s
50ns Typical Driver Propagation Delays with
10ns Skew
s
Pin Compatible with the LTC485
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
Battery-Powered RS485/RS422 Applications
s
Low Power RS485/RS422 Transceiver
s
Level Translator
U
S
A
O
PPLICATI
U
A
O
PPLICATI
TYPICAL
Driver Differential
Output Voltage vs Output Current
3.3V RS485 Network
RO
RE
DE
D1
1
2
3
4
8
7
6
5
LTC1480 TA01
LTC1480
LTC1480
A
A
B
B
A
B
120
120
SHIELD
SHIELD
R
D
3.3V
RO
RE
DE
D1
1
2
3
4
8
7
6
5
LTC1480
R
D
3.3V
3.3V
R
D
1
2
3
4
8
7
6
5
RO
RE
DE D1
OUTPUT CURRENT (mA)
0
0
OUTPUT VOLTAGE (V)
0.5
1.0
1.5
2.0
2.5
60
70
80
LTC1480 TA02
10
20
30
40
50
90
3.0
3.5
V
CC
= 3.3V
T
A
= 25
C
2
LTC1480
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
W
U
U
PACKAGE/ORDER I FOR ATIO
(Note 1)
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
1480
1480I
LTC1480CN8
LTC1480IN8
LTC1480CS8
LTC1480IS8
S8 PART MARKING
ORDER PART
NUMBER
T
JMAX
= 125
C,
JA
= 130
C/ W (N8)
T
JMAX
= 125
C,
JA
= 150
C/ W (S8)
Consult factory for Military grade parts.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
OD1
Differential Driver Output Voltage (Unloaded)
I
O
= 0V
q
3.3
V
V
OD2
Differential Driver Output Voltage (with Load)
R = 27
(RS485), Figure 1
q
1.5
3.3
V
R = 50
(RS422)
q
2.0
V
V
OD
Change in Magnitude of Driver Differential Output
R = 27
or R = 50
, Figure 1
q
0.2
V
Voltage for Complementary Output States
V
OC
Driver Common-Mode Output Voltage
R = 27
or R = 50
, Figure 1
q
2
V
V
OC
Change in Magnitude of Driver Common-Mode
R = 27
or R = 50
, Figure 1
q
0.2
V
Output Voltage for Complementary Output States
V
IH
Input HIGH Voltage
DE, DI, RE
q
2
V
V
IL
Input LOW Voltage
DE, DI, RE
q
0.8
V
I
IN1
Input Current
DE, DI, RE
q
2
A
I
IN2
Input Current (A, B)
DE = 0, V
CC
= 0V or 3.6V, V
IN
= 12V
q
1.0
mA
DE = 0, V
CC
= 0V or 3.6V, V
IN
= 7V
q
0.8
mA
V
TH
Differential Input Threshold Voltage for Receiver
7V
V
CM
12V
q
0.2
0.2
V
V
TH
Receiver Input Hysteresis
V
CM
= 0V
70
mV
V
OH
Receiver Output HIGH Voltage
I
O
= 4mA, V
ID
= 200mV
q
2
V
V
OL
Receiver Output LOW Voltage
I
O
= 4mA, V
ID
= 200mV
q
0.4
V
I
OZR
Three-State (High Impedance) Output
V
CC
= Max, 0.4V
V
O
2.4V
q
1
A
Current at Receiver
R
IN
Receiver Input Resistance
7V
V
CM
12V
q
12
k
I
CC
Supply Current
No Load, Output Enabled
q
400
600
A
No Load, Output Disabled
q
300
500
A
I
SHDN
Supply Current in Shutdown Mode
DE = 0, RE = V
CC
1
10
A
I
OSD1
Driver Short-Circuit Current, V
OUT
= HIGH
7V
V
O
12V
q
35
250
mA
I
OSD2
Driver Short-Circuit Current, V
OUT
= LOW
7V
V
O
12V
q
35
250
mA
I
OSR
Receiver Short-Circuit Current
0V
V
O
V
CC
q
7
85
mA
ELECTRICAL C
C
HARA TERISTICS
V
CC
= 3.3V (Notes 2, 3)
1
2
3
4
8
7
6
5
TOP VIEW
V
CC
B
A
GND
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
R
D
RO
RE
DE
DI
3
LTC1480
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
t
PLH
Driver Input to Output
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
25
50
80
ns
(Figures 3 and 5)
t
PHL
Driver Input to Output
q
25
50
80
t
SKEW
Driver Output to Output
q
10
20
t
R
, t
F
Driver Rise or Fall Time
q
5
15
40
t
ZH
Driver Enable to Output HIGH
C
L
= 100pF (Figures 4, 6), S2 Closed
q
70
120
ns
t
ZL
Driver Enable to Output LOW
C
L
= 100pF (Figures 4, 6), S1 Closed
q
70
120
ns
t
LZ
Driver Disable Time from LOW
C
L
= 15pF (Figures 4, 6), S1 Closed
q
70
120
ns
t
HZ
Driver Disable Time from HIGH
C
L
= 15pF (Figures 4, 6), S2 Closed
q
70
120
ns
t
PLH
Receiver Input to Output
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
30
140
200
ns
(Figure 3, 7)
t
PHL
Receiver Input to Output
q
30
140
200
ns
t
SKD
t
PLH
t
PHL
Differential Receiver Skew
13
ns
t
ZL
Receiver Enable to Output LOW
C
RL
= 15pF (Figures 2, 8), S1 Closed
q
50
80
ns
t
ZH
Receiver Enable to Output HIGH
C
RL
= 15pF (Figures 2, 8), S2 Closed
q
50
80
ns
t
LZ
Receiver Disable from LOW
C
RL
= 15pF (Figures 2, 8), S1 Closed
q
50
80
ns
t
HZ
Receiver Disable from HIGH
C
RL
= 15pF (Figures 2, 8), S2 Closed
q
50
80
ns
f
MAX
Maximum Data Rate
q
2.5
Mbits/s
t
SHDN
Time to Shutdown
DE = 0, RE =
q
50
200
600
ns
t
ZH(SHDN)
Driver Enable from Shutdown to Output HIGH
C
L
= 100pF (Figures 4, 6), S2 Closed
q
70
120
ns
t
ZL(SHDN)
Driver Enable from Shutdown to Output LOW
C
L
= 100pF (Figures 4, 6), S1 Closed
q
70
120
ns
t
ZH(SHDN)
Receiver Enable from Shutdown to Output HIGH
C
L
= 15pF (Figures 2, 8), S2 Closed
q
4500
ns
t
ZL(SHDN)
Receiver Enable from Shutdown to Output LOW
C
L
= 15pF (Figures 2, 8), S1 Closed
q
4500
ns
SWITCHI G CHARACTERISTICS
U
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.
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.
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
V
CC
= 3.3V (Notes 2, 3)
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (mA)
50
100
150
1.5
2.5
LT1480 TPC02
0
50
0.5
1.0
2.0
3.0
3.5
100
150
V
CC
= 3.3V
T
A
= 25
C
Driver Output Low/High Voltage
vs Output Current
Supply Current vs Temperature
TEMPERATURE (
C)
25
200
SUPPLY CURRENT (
A)
225
275
300
325
75
425
LT1480 TPC01
250
25
175
125
50
50
0
150
100
350
375
400
DRIVER DISABLED
THERMAL SHUTDOWN
WITH DRIVER ENABLED
V
CC
= 3.3V
Driver Differential Output Voltage
vs Temperature
TEMPERATURE (
C)
40
1.9
2.0
2.2
20
60
LT
C1480 TPC03
1.8
1.7
20
0
40
80
100
1.6
1.5
2.1
DIFFERENTIAL VOLTAGE (V)
R
L
= 100
R
L
= 54
V
CC
= 3.3V
4
LTC1480
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
PI
N
FU
N
CTIO
N
S
U
U
U
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.
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 (1
A) shutdown state. If RE is low and DE is
Receiver Output Low Voltage
vs Output Current
Receiver Output High Voltage
vs Output Current
OUTPUT VOLTAGE (V)
3.30
OUTPUT CURRENT (mA)
8
10
12
1.30
LT1480 TPC06
6
4
0
2.80
2.30
1.80
2
16
14
3.05
2.55
2.05
1.55
V
CC
= 3.3V
T
A
= 25
C
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (mA)
15
20
25
1.6
LTC1480 TPC05
10
5
0
0.2 0.4 0.6
1.0
1.4
1.8
0.8
1.2
2.0
V
CC
= 3.3V
T
A
= 25
C
Driver Skew vs Temperature
TEMPERATURE (
C)
40
TIME (ns)
6.5
20
LT1480 TPC04
5.0
4.0
20
0
40
3.5
3.0
7.0
6.0
5.5
4.5
60
80
100
V
CC
= 3.3V
Receiver
t
PLH
t
PHL
vs Temperature
TEMPERATURE (
C)
40
TIME (ns)
12
10
8
6
4
2
0
20
60
LT1480 TPC07
20
0
40
80
100
V
CC
= 3.3V
Receiver Output Low Voltage
vs Temperature
TEMPERATURE (
C)
40
OUTPUT VOLTAGE (V)
0.4
0.5
0.6
20
60
LTC1480 TPC08
0.3
0.2
20
0
40
80
100
0.1
0
V
CC
= 3.3V
1 = 8mA
Receiver Output High Voltage
vs Temperature
TEMPERATURE (
C)
40
2.0
OUTPUT VOLTAGE (V)
2.4
3.0
0
40
60
LTC1480 TPC09
2.2
2.8
2.6
20
20
80
100
V
CC
= 3.3V
1 = 8mA
5
LTC1480
FU CTIO TABLES
U
U
LTC1480 Transmitting
INPUTS
OUTPUTS
RE
DE
DI
B
A
X
1
1
0
1
X
1
0
1
0
0
0
X
Z
Z
1
0
X
Z*
Z*
*Shutdown mode
LTC1480 Receiving
INPUTS
OUTPUTS
RE
DE
A B
RO
0
0
0.2V
1
0
0
0.2V
0
0
0
Inputs Open
1
1
0
X
Z*
*Shutdown mode
Figure 2. Receiver Timing Test Load
Figure 1. Driver DC Test Load
Figure 5. Driver Propagation Delays
SWITCHI G TI E WAVEFOR S
U
W
W
Figure 4. Driver Timing Test Load
Figure 3. Driver/Receiver Timing Test Circuit
V
OD
A
B
R
R
V
OC
LTC1480 F01
RECEIVER
OUTPUT
C
RL
1k
S1
S2
TEST POINT
V
CC
1k
LTC1480 F02
3V
DE
A
B
DI
R
DIFF
C
L1
C
L2
RO
15pF
A
B
RE
LTC1480 F03
LTC1480
RECEIVER
LTC1480
DRIVER
OUTPUT
UNDER TEST
C
L
S1
S2
V
CC
500
LTC1480 F04
DI
3V
1.5V
t
PLH
t
r
t
SKEW
1/2 V
O
V
O
f = 1MHz, t
r
10ns, t
f
10ns
90%
10%
0V
B
A
V
O
V
O
0V
90%
1.5V
t
PHL
t
SKEW
1/2 V
O
10%
t
f
V
DIFF
= V(A) V(B)
LTC1480 F05
TEST CIRCUITS
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