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1
LTC1482
Low Power RS485 Transceiver
with Carrier Detect and
Receiver Fail-Safe
s
No Damage or Latchup to
15kV (Human Body
Model), IEC1000-4-2 Level 4 (
8kV) Contact and
Level 3 (
8kV) Air Discharge
s
Active Low Carrier Detect Output
s
Guaranteed High Receiver Output State for
Floating, Shorted or Terminated Inputs with
No Signal Present
s
Drives Low Cost Residential Telephone Wires
s
Low Power: I
CC
= 700
A Max with Driver Disabled
s
I
CC
= 900
A Max in Driver Mode Without Load
s
20
A Max Quiescent Current in Shutdown Mode
s
Single 5V Supply
s
7V to 12V Common Mode Range Permits
7V
Ground Difference Between Devices on the Data Line
s
Maximum Data Rate of 4Mbps
s
Power Up/Down Glitch-Free Driver Outputs
s
Up to 32 Transceivers on the Bus
s
Available in 8-Lead MSOP, PDIP and SO Packages
The LTC
1482 is a low power RS485 compatible trans-
ceiver that offers an active low carrier detect output. The
open-drain carrier detect pin allows several transceivers
to share the same carrier detect line and can be used to
detect the insertion or removal of a driven RS485/RS422
cable.
Enhanced ESD protection allows the LTC1482 to with-
stand
15kV (human body model), IEC-1000-4-2 level 4
(
8kV) contact and level 3 (
8kV) air discharge ESD
without latchup or damage.
The LTC1482 receiver stays alive at all times except in
shutdown. The supply current is a maximum of 700
A
and 900
A when the driver is disabled and enabled
respectively. In shutdown, the quiescent current of the
LTC1482 drops to a maximum of 20
A.
When the driver is disabled or the LTC1482 is in shut-
down, the driver outputs are three-stated and remain in
a high impedance state over the RS485 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 LTC1482 is fully specified over the commercial and
industrial temperature ranges and is available in 8-lead
MSOP, PDIP and SO packages.
s
Battery-Powered RS485/RS422 Applications
s
Low Power RS485/RS422 Transceiver
s
Level Translator
, LTC and LT are registered trademarks of Linear Technology Corporation.
RO1
CD1
DE1
DI1/SHDN1
R
V
CC1
LTC1482
GND1
B1
A1
B2
A2
120
120
D
V
CC2
GND2
1482 TA01
R
D
RO2
CD2
DE2
DI2/SHDN2
LTC1482
RS485 Interface
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
U
Carrier Detect Output (2000 Foot STP Cable)
DE1
Dl1 = V
CC
1482 TA01a
DE2 = 0
Dl2 = V
CC
1k PULL-UP AT CD
DE1
A2
B2
CD2
2
LTC1482
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
(Note 1)
Supply Voltage (V
CC
)............................................... 6.5V
Control Input Voltages ................. 0.3V to (V
CC
+ 0.3V)
Carrier Detect Voltage ................................. 0.3V to 8V
Driver Input Voltage ..................... 0.3V to (V
CC
+ 0.3V)
Driver Output Voltages ................................. 7V to 10V
Receiver Input Voltages (Driver Disabled) .. 12V to 14V
Receiver Output Voltage ............... 0.3V to (V
CC
+ 0.3V)
Junction Temperature .......................................... 125
C
Operating Temperature Range
LTC1482C ........................................ 0
C
T
A
70
C
LTC1482I ...................................... 40
C
T
A
85
C
Storage Temperature Range .................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................... 300
C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
OD1
Differential Driver Output Voltage (Unloaded)
I
OUT
= 0
q
V
CC
V
V
OD2
Differential Driver Output Voltage (with Load)
R = 50
(RS422)
q
2
V
R = 27
(RS485) Figure 1
q
1.5
5
V
R = 22
, Figure 1
q
1.5
5
V
V
OD3
Differential Driver Output Voltage
V
TST
= 7V to 12V, Figure 2
q
1.5
5
V
(with Common Mode)
V
OD
Change in Magnitude of Driver Differential
R = 22
, 27
or R = 50
, Figure 1
q
0.2
V
Output Voltage for Complementary Output States
V
TST
= 7V to 12V, Figure 2
V
OC
Driver Common Mode Output Voltage
R = 22
, 27
or R = 50
, Figure 1
q
3
V
|V
OC
|
Change in Magnitude of Driver Common Mode
R = 22
, 27
or R = 50
, Figure 1
q
0.2
V
Output Voltage for Complementary Output States
V
IH
Input High Voltage
DE, DI/SHDN
q
2
V
V
IL
Input Low Voltage
DE, DI/SHDN
q
0.8
V
I
IN1
Input Current
DE, DI/SHDN
q
2
A
I
IN2
Input Current (A, B) with Driver Disabled
DE = 0, V
CC
= 0 or 5V, V
IN
= 12V
q
1.0
mA
DE = 0, V
CC
= 0 or 5V, V
IN
= 7V
q
0.8
mA
V
THRO
Differential Input Threshold Voltage for Receiver
7V
V
CM
12V, DE = 0
q
0.20
0.015
V
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V
5% (Notes 2 and 3) unless otherwise noted.
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
ORDER PART
NUMBER
ORDER PART
NUMBER
LTC1482CMS8
LTC1482CN8
LTC1482CS8
LTC1482IN8
LTC1482IS8
S8 PART MARKING
1482
1482I
MS8 PART MARKING
LTCB
T
JMAX
= 125
C,
JA
= 200
C/ W
1
2
3
4
RO
CD
DE
DI/SHDN
8
7
6
5
V
CC
B
A
GND
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125
C,
JA
= 130
C/ W (N8)
T
JMAX
= 125
C,
JA
= 135
C/ W (S8)
1
2
3
4
8
7
6
5
TOP VIEW
RO
CD
DE
DI/SHDN
V
CC
B
A
GND
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
Consult factory for Military grade parts.
3
LTC1482
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V
5% (Notes 2 and 3) unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
THCD
Differential Input Threshold Voltage for CD = 1
7V
V
CM
12V, DE = 0
q
0.20
0.20
V
V
TH
Receiver Input Hysteresis
V
CM
= 0V, DE = 0
30
mV
V
OH
CD Output High Voltage
I
OUT
= 10
A, (V
A
V
B
) = 0V
q
3.4
V
RO Output High Voltage
I
OUT
= 4mA, (V
A
V
B
) = 200mV
q
3.5
V
V
OL
RO and CD Output Low Voltage
I
OUT
= 4mA, (V
A
V
B
) = 200mV
q
0.4
V
I
OZR
Three-State (High Impedance) Receiver Output
V
CC
= Max, 0.4V
V
OUT
2.4V
q
1
A
Current in Shutdown
DI/SHDN = 0, DE = 0
R
IN
Receiver Input Resistance
7V
V
CM
12V
q
12
22
k
I
CC
Supply Current
No Load, Driver Enabled (DE = V
CC
)
q
580
900
A
No Load, Driver Disabled (DE = 0)
q
430
700
A
I
SHDN
Supply Current in Shutdown Mode
DE = 0, DI = 0
q
10
20
A
I
OSD1
Driver Short-Circuit Current, V
OUT
= High (Note 4)
7V
V
OUT
10V
35
250
mA
I
OSD2
Driver Short-Circuit Current, V
OUT
= Low (Note 4)
7V
V
OUT
10V
35
250
mA
I
OS
RO and CD Short-Circuit Current
0V
V
OUT
V
CC
q
7
85
mA
I
PULL-UP
CD Pull-Up Current
CD = 0V
q
15
30
60
A
SWITCHI
N
G CHARACTERISTICS
U
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V
5% (Notes 2 and 3) unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
t
PLH
Driver Input to Output
R
DIFF
= 54
, C
L1
= C
L2
= 100pF
q
10
28
60
ns
t
PHL
Driver Input to Output
(Figures 4, 6)
q
10
30
60
ns
t
SKEW
Driver Output to Output
q
2
10
ns
t
r
, t
f
Driver Rise or Fall Time
q
3
15
40
ns
t
ZH
Driver Enable to Output High
C
L
= 100pF (Figures 5, 7) S2 Closed
q
40
70
ns
t
ZL
Driver Enable to Output Low
C
L
= 100pF (Figures 5, 7) S1 Closed
q
40
100
ns
t
LZ
Driver Disable Time from Low
C
L
= 15pF (Figures 5, 7) S1 Closed
q
40
70
ns
t
HZ
Driver Disable Time from High
C
L
= 15pF (Figures 5, 7) S2 Closed
q
40
70
ns
t
ZH(SHDN)
Driver Enable from Shutdown to Output High
C
L
= 100pF (Figures 5, 7) S2 Closed
q
40
100
ns
(Note 5)
t
ZL(SHDN)
Driver Enable from Shutdown to Output Low
C
L
= 100pF (Figures 5, 7) S1 Closed
q
40
100
ns
t
HZ(SHDN)
Driver Disable on Shutdown from Output High
C
L
= 15pF (Figures 5, 7) S2 Closed
q
40
100
ns
t
LZ(SHDN)
Driver Disable on Shutdown from Output Low
C
L
= 15pF (Figures 5, 7) S1 Closed
q
40
100
ns
f
MAX
Maximum Data Rate (Note 6)
q
4
5
Mbps
t
PLH
Receiver Input to Output (Note 7)
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
30
138
200
ns
(Figures 4, 8)
t
PHL
Receiver Input to Output
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
30
122
200
ns
(Figures 4, 8)
t
SKD
|t
PLH
t
PHL
| Differential Receiver Skew
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
16
ns
(Figures 4, 8)
t
CDH
Receiver Input to CD Output High (Note 7)
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
2900
5000
ns
(Figures 4, 10) DI/SHDN = V
CC
t
CDL
Receiver Input to CD Output Low (Note 7)
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
150
300
ns
(Figures 4, 10) DI/SHDN = V
CC
4
LTC1482
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
t
CDH(SHDN)
Receiver Input to CD Output High at Shutdown
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
2600
5000
ns
(Figures 4, 11) DI/SHDN = DE
t
CDL(SHDN)
Receiver Input to CD Output Low from Shutdown
R
DIFF
= 54
, C
L1
= C
L2
= 100pF,
q
2600
5000
ns
(Figures 4, 11) DI/SHDN = DE
t
ZH(SHDN)
Receiver Enable from Shutdown to Output High
C
L
= 15pF (Figures 3, 9) S2 Closed,
q
30
600
ns
A = 750mV, B = 750mV, DE = 0,
DI/SHDN =
t
ZL(SHDN)
Receiver Enable from Shutdown to Output Low
C
L
= 15pF (Figures 3, 9) S1 Closed,
q
2600
5000
ns
A = 750mV, B = 750mV, DE = 0,
DI/SHDN =
t
HZ(SHDN)
Receiver Disable from High on Shutdown
C
L
= 15pF (Figures 3, 9) S2 Closed,
q
200
600
ns
A = 750mV, B = 750mV, DE = 0,
DI/SHDN =
t
LZ(SHDN)
Receiver Disable from Low on Shutdown
C
L
= 15pF (Figures 3, 9) S1 Closed,
q
200
600
ns
A = 750mV, B = 750mV, DE = 0,
DI/SHDN =
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V
5% (Notes 2 and 3) unless otherwise noted.
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2: All typicals are given for V
CC
= 5V and T
A
= 25
C.
Note 3: 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.
Note 4: For higher ambient temperatures, the part may enter thermal
shutdown during short-circuit conditions.
Note 5: Both driver input and driver enable pins are pulled high
simultaneously.
Note 6: Guaranteed by design.
Note 7: Measured with an external LTC1485 driver.
SWITCHI
N
G CHARACTERISTICS
U
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Receiver Output Voltage vs Input
Voltage
Receiver Input Threshold Voltage
(Output High) vs Temperature
Receiver Input Threshold Voltage
(Output Low) vs Temperature
INPUT VOLTAGE (V)
0.2
0.16
0.12
0.08
0.04
0
RECEIVER OUTPUT VOLTAGE (V)
1482 G01
6
5
4
3
2
1
0
T
A
= 25
C
V
THRO(HIGH)
V
THRO(LOW)
TEMPERATURE (
C)
55 35 15
5
25
45
65
85 105 125
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
1482 G02
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.20
V
CC
= 5V
V
THRO(HIGH)
V
CM
= 7V
V
CM
= 12V
V
CM
= 0V
TEMPERATURE (
C)
55 35 15
5
25
45
65
85 105 125
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
1482 G03
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.20
V
CC
= 5V
V
THRO(LOW)
V
CM
= 7V
V
CM
= 12V
V
CM
= 0V
5
LTC1482
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Receiver Input Offset Voltage vs
Temperature
Receiver Hysteresis vs
Temperature
Receiver Input Threshold Voltage
vs Supply Voltage
Carrier Detect Output Voltage vs
Receiver Input Voltage
Carrier Detect Threshold Voltage
(Output High) vs Temperature
Carrier Detect Threshold Voltage
(Output Low) vs Temperature
Receiver Output High Voltage vs
Temperature
Carrier Detect Output High
Voltage vs Output Current
Receiver and Carrier Detect
Output Low Voltage vs Output
Current
TEMPERATURE (
C)
55 35 15
5
25
45
65
85 105 125
RECEIVER INPUT OFFSET VOLTAGE (mV)
1482 G04
0
20
40
60
80
100
120
140
160
180
200
V
CC
= 5V
V
CM
= 7V
V
CM
= 12V
V
CM
= 0V
TEMPERATURE (
C)
55 35 15
5
25
45
65
85 105 125
HYSTERESIS (mV)
1482 G05
100
90
80
70
60
50
40
30
20
10
0
V
CC
= 5V
V
CM
= 7V TO 12V
SUPPLY VOLTAGE (V)
4.5
4.75
5
5.25
5.5
RECEIVER INPUT THRESHOLD VOLTAGE (V)
1482 G06
0
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
T
A
= 25
C
V
THRO(HIGH)
V
THRO(LOW)
RECEIVER INPUT VOLTAGE (V)
0.25
0.15
0.05
0.05
0.15
0.25
CARRIER DETECT OUTPUT VOLTAGE (V)
1482 G07
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
POSITIVE
V
THCD(LOW)
NEGATIVE
V
THCD(LOW)
NEGATIVE, V
THCD(HIGH)
POSITIVE, V
THCD(HIGH)
TEMPERATURE (
C)
CARRIER DETECT THRESHOLD VOLTAGE (V)
1482 G08
0.25
0.20
0.15
0.10
0.05
0
0.05
0.10
0.15
0.20
0.25
V
CC
= 5V
POSITIVE
V
THCD(HIGH)
NEGATIVE
V
THCD(HIGH)
55 35 15
5
25
45
65
85 105 125
V
CM
= 12V
V
CM
= 7V
V
CM
= 0V
V
CM
= 12V
V
CM
= 7V
V
CM
= 0V
TEMPERATURE (
C)
CARRIER DETECT THRESHOLD VOLTAGE (V)
1482 G09
0.25
0.20
0.15
0.10
0.05
0
0.05
0.10
0.15
0.20
0.25
V
CC
= 5V
POSITIVE
V
THCD(LOW)
NEGATIVE
V
THCD(LOW)
55 35 15
5
25
45
65
85 105 125
V
CM
= 12V
V
CM
= 7V
V
CM
= 12V
V
CM
= 7V
V
CM
= 0V
V
CM
= 0V
TEMPERATURE (
C)
55 35 15
5
25
45
65
85 105 125
RECEIVER OUTPUT HIGH VOLTAGE (V)
1482 G10
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
3.6
3.5
V
CC
= 4.75V
I
OUT
= 8mA
OUTPUT CURRENT (
A)
35
30
25
20
15
10
5
0
CARRIER DETECT OUTPUT HIGH VOLTAGE (V)
1482 G11
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
CC
= 4.75V
T
A
= 25
C
OUTPUT LOW VOLTAGE (V)
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
2
OUTPUT CURRENT (mA)
1482 G12
40
35
30
25
20
15
10
5
0
T
A
= 25
C
V
CC
= 4.75
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