LTC1482
Low Power RS485 Transceiver
with Carrier Detect and
Receiver Fail-Safe
DESCRIPTIO
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 700µA
and 900µA when the driver is disabled and enabled
respectively. In shutdown, the quiescent current of the
LTC1482 drops to a maximum of 20µA.
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.
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
s
No Damage or Latchup to
±
15kV (Human Body
Model), IEC1000-4-2 Level 4 (
±
8kV) Contact and
Level 3 (
±
8kV) Air Discharge
Active Low Carrier Detect Output
Guaranteed High Receiver Output State for
Floating, Shorted or Terminated Inputs with
No Signal Present
Drives Low Cost Residential Telephone Wires
Low Power: I
CC
= 700µA Max with Driver Disabled
I
CC
= 900µA Max in Driver Mode Without Load
20µA Max Quiescent Current in Shutdown Mode
Single 5V Supply
– 7V to 12V Common Mode Range Permits
±7V
Ground Difference Between Devices on the Data Line
Maximum Data Rate of 4Mbps
Power Up/Down Glitch-Free Driver Outputs
Up to 32 Transceivers on the Bus
Available in 8-Lead
MSOP,
PDIP and SO Packages
APPLICATIO S
s
s
s
Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
LTC1482
RO1
CD1
DE1
D
DI1/SHDN1
GND1
R
B1
A1
V
CC1
Carrier Detect Output (2000 Foot STP Cable)
RS485 Interface
DE1
LTC1482
V
CC2
B2
120Ω
120Ω
GND2
1482 TA01
RO2
R
CD2
DE2
D
DI2/SHDN2
CD2
A2
B2
A2
DE1
↑↓
DE2 = 0
1k PULL-UP AT CD
U
U
U
Dl1 = V
CC
Dl2 = V
CC
1482 TA01a
1
LTC1482
ABSOLUTE
MAXIMUM
RATINGS
(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)
PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
RO
CD
DE
DI/SHDN
1
2
3
4
8
7
6
5
V
CC
B
A
GND
LTC1482CMS8
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 200°C/ W
MS8 PART MARKING
LTCB
Consult factory for Military grade parts.
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
V
OD1
V
OD2
PARAMETER
Differential Driver Output Voltage (Unloaded)
Differential Driver Output Voltage (with Load)
CONDITIONS
I
OUT
= 0
R = 50Ω (RS422)
R = 27Ω (RS485) Figure 1
R = 22Ω, Figure 1
V
TST
= – 7V to 12V, Figure 2
R = 22Ω, 27Ω or R = 50Ω, Figure 1
V
TST
= – 7V to 12V, Figure 2
R = 22Ω, 27Ω or R = 50Ω, Figure 1
R = 22Ω, 27Ω or R = 50Ω, Figure 1
DE, DI/SHDN
DE, DI/SHDN
DE, DI/SHDN
DE = 0, V
CC
= 0 or 5V, V
IN
= 12V
DE = 0, V
CC
= 0 or 5V, V
IN
= –7V
– 7V
≤
V
CM
≤
12V, DE = 0
q
q
q
q
q
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
V
OD3
∆V
OD
V
OC
∆|V
OC
|
V
IH
V
IL
I
IN1
I
IN2
V
THRO
Differential Driver Output Voltage
(with Common Mode)
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) with Driver Disabled
Differential Input Threshold Voltage for Receiver
2
U
U
W
W W
U
W
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
TOP VIEW
RO 1
CD 2
DE 3
DI/SHDN 4
N8 PACKAGE
8-LEAD PDIP
8
7
6
5
V
CC
B
A
GND
ORDER PART
NUMBER
LTC1482CN8
LTC1482CS8
LTC1482IN8
LTC1482IS8
S8 PART MARKING
1482
1482I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 130°C/ W (N8)
T
JMAX
= 125°C,
θ
JA
= 135°C/ W (S8)
MIN
2
1.5
1.5
1.5
TYP
MAX
V
CC
5
5
5
0.2
3
0.2
UNITS
V
V
V
V
V
V
V
V
V
2
0.8
±2
1.0
– 0.8
– 0.20
– 0.015
V
µA
mA
mA
V
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.
SYMBOL
V
THCD
∆V
TH
V
OH
V
OL
I
OZR
R
IN
I
CC
I
SHDN
I
OSD1
I
OSD2
I
OS
I
PULL-UP
PARAMETER
Differential Input Threshold Voltage for CD = 1
Receiver Input Hysteresis
CD Output High Voltage
RO Output High Voltage
RO and CD Output Low Voltage
Three-State (High Impedance) Receiver Output
Current in Shutdown
Receiver Input Resistance
Supply Current
Supply Current in Shutdown Mode
Driver Short-Circuit Current, V
OUT
= High (Note 4)
Driver Short-Circuit Current, V
OUT
= Low (Note 4)
RO and CD Short-Circuit Current
CD Pull-Up Current
CONDITIONS
– 7V
≤
V
CM
≤
12V, DE = 0
V
CM
= 0V, DE = 0
I
OUT
= – 10µA, (V
A
– V
B
) = 0V
I
OUT
= – 4mA, (V
A
– V
B
) = 200mV
I
OUT
= 4mA, (V
A
– V
B
) = – 200mV
V
CC
= Max, 0.4V
≤
V
OUT
≤
2.4V
DI/SHDN = 0, DE = 0
–7V
≤
V
CM
≤
12V
No Load, Driver Enabled (DE = V
CC
)
No Load, Driver Disabled (DE = 0)
DE = 0, DI = 0
– 7V
≤
V
OUT
≤
10V
– 7V
≤
V
OUT
≤
10V
0V
≤
V
OUT
≤
V
CC
CD = 0V
q
q
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
– 0.20
TYP
±30
MAX
0.20
UNITS
V
mV
V
V
3.4
3.5
0.4
±1
12
22
580
430
10
35
35
7
15
30
900
700
20
250
250
85
60
V
µA
kΩ
µA
µA
µA
mA
mA
mA
µA
SWITCHING CHARACTERISTICS
SYMBOL
t
PLH
t
PHL
t
SKEW
t
r
, t
f
t
ZH
t
ZL
t
LZ
t
HZ
t
ZH(SHDN)
t
ZL(SHDN)
t
HZ(SHDN)
t
LZ(SHDN)
f
MAX
t
PLH
t
PHL
t
SKD
t
CDH
t
CDL
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
Driver Enable from Shutdown to Output High
(Note 5)
Driver Enable from Shutdown to Output Low
Driver Disable on Shutdown from Output High
Driver Disable on Shutdown from Output Low
Maximum Data Rate (Note 6)
Receiver Input to Output (Note 7)
Receiver Input to Output
|t
PLH
– t
PHL
| Differential Receiver Skew
Receiver Input to CD Output High (Note 7)
Receiver Input to CD Output Low (Note 7)
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.
CONDITIONS
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
(Figures 4, 6)
q
q
q
q
U
MIN
10
10
3
TYP
28
30
2
15
40
40
40
40
40
40
40
40
MAX
60
60
10
40
70
100
70
70
100
100
100
100
200
200
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Mbps
ns
ns
ns
C
L
= 100pF (Figures 5, 7) S2 Closed
C
L
= 100pF (Figures 5, 7) S1 Closed
C
L
= 15pF (Figures 5, 7) S1 Closed
C
L
= 15pF (Figures 5, 7) S2 Closed
C
L
= 100pF (Figures 5, 7) S2 Closed
C
L
= 100pF (Figures 5, 7) S1 Closed
C
L
= 15pF (Figures 5, 7) S2 Closed
C
L
= 15pF (Figures 5, 7) S1 Closed
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 4, 8)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 4, 8)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 4, 8)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 4, 10) DI/SHDN = V
CC
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 4, 10) DI/SHDN = V
CC
q
q
q
q
q
q
q
q
q
q
q
4
30
30
5
138
122
16
q
q
2900
150
5000
300
ns
ns
3
LTC1482
SWITCHING CHARACTERISTICS
SYMBOL
PARAMETER
t
CDH(SHDN)
Receiver Input to CD Output High at Shutdown
t
CDL(SHDN)
Receiver Input to CD Output Low from Shutdown
t
ZH(SHDN)
Receiver Enable from Shutdown to Output High
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.
CONDITIONS
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 4, 11) DI/SHDN = DE
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF,
(Figures 4, 11) DI/SHDN = DE
C
L
= 15pF (Figures 3, 9) S2 Closed,
A = 750mV, B = – 750mV, DE = 0,
DI/SHDN =
C
L
= 15pF (Figures 3, 9) S1 Closed,
A = – 750mV, B = 750mV, DE = 0,
DI/SHDN =
C
L
= 15pF (Figures 3, 9) S2 Closed,
A = 750mV, B = – 750mV, DE = 0,
DI/SHDN =
C
L
= 15pF (Figures 3, 9) S1 Closed,
A = – 750mV, B = 750mV, DE = 0,
DI/SHDN =
q
q
q
t
ZL(SHDN)
Receiver Enable from Shutdown to Output Low
t
HZ(SHDN)
Receiver Disable from High on Shutdown
t
LZ(SHDN)
Receiver Disable from Low on Shutdown
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.
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Output Voltage vs Input
Voltage
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
6
T
A
= 25°C
RECEIVER OUTPUT VOLTAGE (V)
5
4
3
2
1
0
–0.2
0
–0.02
–0.04
–0.06
–0.08
–0.1
–0.12
–0.14
–0.16
–0.18
–0.20
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G02
V
CM
= 12V
V
CC
= 5V
V
THRO(HIGH)
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
V
THRO(LOW)
–0.16
V
THRO(HIGH)
0
1482 G01
–0.12
–0.08
–0.04
INPUT VOLTAGE (V)
4
U W
U
MIN
TYP
2600
2600
30
MAX
5000
5000
600
UNITS
ns
ns
ns
q
2600
5000
ns
q
200
600
ns
q
200
600
ns
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.
Receiver Input Threshold Voltage
(Output High) vs Temperature
0
–0.02
–0.04
–0.06
–0.08
–0.1
–0.12
–0.14
–0.16
–0.18
Receiver Input Threshold Voltage
(Output Low) vs Temperature
V
CC
= 5V
V
THRO(LOW)
V
CM
= 12V
V
CM
= 0V
V
CM
= –7V
V
CM
= 0V
V
CM
= –7V
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G03
–0.20
–55 –35 –15
LTC1482
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Offset Voltage vs
Temperature
0
RECEIVER INPUT OFFSET VOLTAGE (mV)
–20
–40
V
CC
= 5V
90
80
HYSTERESIS (mV)
70
60
50
40
30
20
10
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G04
V
CC
= 5V
RECEIVER INPUT THRESHOLD VOLTAGE (V)
–60
–80
–100
–120
–140
–160
–180
–200
–55 –35 –15
V
CM
= 0V
V
CM
= –7V
V
CM
= 12V
Carrier Detect Output Voltage vs
Receiver Input Voltage
CARRIER DETECT THRESHOLD VOLTAGE (V)
CARRIER DETECT THRESHOLD VOLTAGE (V)
5.0
CARRIER DETECT OUTPUT VOLTAGE (V)
4.5
4.0
3.5
NEGATIVE, V
THCD(HIGH)
3.0
2.5
NEGATIVE
V
THCD(LOW)
2.0
1.5
1.0
0.5
0
–0.25
–0.15
–0.05
0.05
0.15
RECEIVER INPUT VOLTAGE (V)
0.25
1482 G07
POSITIVE, V
THCD(HIGH)
POSITIVE
V
THCD(LOW)
Receiver Output High Voltage vs
Temperature
RECEIVER OUTPUT HIGH VOLTAGE (V)
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
3.6
3.5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G10
V
CC
= 4.75V
I
OUT
= –8mA
CARRIER DETECT OUTPUT HIGH VOLTAGE (V)
4.5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–35
–30
–25 –20 –15 –10
OUTPUT CURRENT (µA)
–5
0
OUTPUT CURRENT (mA)
U W
Receiver Hysteresis vs
Temperature
100
0
–0.02
–0.04
–0.06
–0.08
–0.10
–0.12
–0.14
–0.16
–0.18
–0.20
Receiver Input Threshold Voltage
vs Supply Voltage
T
A
= 25°C
V
THRO(HIGH)
V
CM
= –7V TO 12V
V
THRO(LOW)
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G05
4.5
4.75
5
5.25
SUPPLY VOLTAGE (V)
5.5
1482 G06
Carrier Detect Threshold Voltage
(Output High) vs Temperature
0.25
0.20
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
V
CC
= 5V
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G08
Carrier Detect Threshold Voltage
(Output Low) vs Temperature
0.25
0.20
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
V
CC
= 5V
V
CM
= 0V
V
CM
= –7V
NEGATIVE
V
THCD(LOW)
V
CM
= 12V
V
CM
= 0V
POSITIVE
V
THCD(LOW)
V
CM
= 12V
V
CM
= –7V
POSITIVE
V
THCD(HIGH)
V
CM
= 12V
V
CM
= –7V
NEGATIVE
V
THCD(HIGH)
V
CM
= 0V
V
CM
= 12V
V
CM
= 0V
V
CM
= –7V
–0.25
–55 –35 –15
–0.25
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G09
Carrier Detect Output High
Voltage vs Output Current
5.0
4.5
4.0
30
25
20
15
10
5
0
V
CC
= 4.75V
T
A
= 25°C
40
35
Receiver and Carrier Detect
Output Low Voltage vs Output
Current
T
A
= 25°C
V
CC
= 4.75
0
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
OUTPUT LOW VOLTAGE (V)
2
1482 G11
1482 G12
5
嵌入式系统
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