LTC1482
Low Power RS485 Transceiver
with Carrier Detect and
Receiver Fail-Safe
DESCRIPTIO
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FEATURES
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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: ICC = 700µA Max with Driver Disabled
ICC = 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
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APPLICATIO S
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The LTC®1482 is a low power RS485 compatible transceiver 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 withstand ±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 shutdown, 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.
Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
The LTC1482 is fully specified over the commercial and
industrial temperature ranges and is available in 8-lead
MSOP, PDIP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Carrier Detect Output (2000 Foot STP Cable)
RS485 Interface
DE1
LTC1482
LTC1482
VCC1
RO1
R
CD1
A1
DE1
B2
120Ω
120Ω
D
DI1/SHDN1
RO2
VCC2
B1
R
A2
D
GND1
CD2
A2
DE2
B2
DI2/SHDN2
GND2
CD2
1482 TA01
DE1 ↑↓
DE2 = 0
1k PULL-UP AT CD
Dl1 = VCC
Dl2 = VCC
1482 TA01a
1
LTC1482
W W
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (VCC)............................................... 6.5V
Control Input Voltages ................. – 0.3V to (VCC + 0.3V)
Carrier Detect Voltage ................................. – 0.3V to 8V
Driver Input Voltage ..................... – 0.3V to (VCC + 0.3V)
Driver Output Voltages ................................. – 7V to 10V
Receiver Input Voltages (Driver Disabled) .. –12V to 14V
Receiver Output Voltage ............... – 0.3V to (VCC + 0.3V)
Junction Temperature .......................................... 125°C
Operating Temperature Range
LTC1482C ........................................ 0°C ≤ TA ≤ 70°C
LTC1482I ...................................... – 40°C ≤ TA ≤ 85°C
Storage Temperature Range .................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
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W
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PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
RO
CD
DE
DI/SHDN
1
2
3
4
8
7
6
5
LTC1482CMS8
VCC
B
A
GND
MS8 PACKAGE
8-LEAD PLASTIC MSOP
MS8 PART MARKING
TJMAX = 125°C, θJA = 200°C/ W
ORDER PART
NUMBER
TOP VIEW
RO 1
8
VCC
CD 2
7
B
DE 3
6
A
DI/SHDN 4
5
GND
N8 PACKAGE
8-LEAD PDIP
LTC1482CN8
LTC1482CS8
LTC1482IN8
LTC1482IS8
S8 PACKAGE
8-LEAD PLASTIC SO
S8 PART MARKING
TJMAX = 125°C, θJA = 130°C/ W (N8)
TJMAX = 125°C, θJA = 135°C/ W (S8)
LTCB
1482
1482I
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VOD1
Differential Driver Output Voltage (Unloaded)
IOUT = 0
●
MIN
VOD2
Differential Driver Output Voltage (with Load)
R = 50Ω (RS422)
R = 27Ω (RS485) Figure 1
R = 22Ω, Figure 1
●
●
●
TYP
MAX
UNITS
VCC
V
2
1.5
1.5
5
5
V
V
V
1.5
5
V
VOD3
Differential Driver Output Voltage
(with Common Mode)
VTST = – 7V to 12V, Figure 2
●
∆VOD
Change in Magnitude of Driver Differential
Output Voltage for Complementary Output States
R = 22Ω, 27Ω or R = 50Ω, Figure 1
VTST = – 7V to 12V, Figure 2
●
0.2
V
VOC
Driver Common Mode Output Voltage
R = 22Ω, 27Ω or R = 50Ω, Figure 1
●
3
V
∆|VOC|
Change in Magnitude of Driver Common Mode
Output Voltage for Complementary Output States
R = 22Ω, 27Ω or R = 50Ω, Figure 1
●
0.2
V
VIH
Input High Voltage
DE, DI/SHDN
●
VIL
Input Low Voltage
DE, DI/SHDN
●
0.8
V
IIN1
Input Current
DE, DI/SHDN
●
±2
µA
IIN2
Input Current (A, B) with Driver Disabled
DE = 0, VCC = 0 or 5V, VIN = 12V
DE = 0, VCC = 0 or 5V, VIN = –7V
●
●
1.0
– 0.8
mA
mA
VTHRO
Differential Input Threshold Voltage for Receiver
– 7V ≤ VCM ≤ 12V, DE = 0
●
2
2
– 0.20
V
– 0.015
V
LTC1482
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VTHCD
Differential Input Threshold Voltage for CD = 1
– 7V ≤ VCM ≤ 12V, DE = 0
∆VTH
Receiver Input Hysteresis
VCM = 0V, DE = 0
VOH
CD Output High Voltage
MIN
TYP
MAX
UNITS
0.20
V
●
– 0.20
IOUT = – 10µA, (VA – VB) = 0V
●
3.4
V
RO Output High Voltage
IOUT = – 4mA, (VA – VB) = 200mV
●
3.5
V
VOL
RO and CD Output Low Voltage
IOUT = 4mA, (VA – VB) = – 200mV
●
0.4
V
IOZR
Three-State (High Impedance) Receiver Output
Current in Shutdown
VCC = Max, 0.4V ≤ VOUT ≤ 2.4V
DI/SHDN = 0, DE = 0
●
±1
µA
RIN
Receiver Input Resistance
–7V ≤ VCM ≤ 12V
●
ICC
Supply Current
No Load, Driver Enabled (DE = VCC)
No Load, Driver Disabled (DE = 0)
●
●
ISHDN
Supply Current in Shutdown Mode
DE = 0, DI = 0
●
20
µA
IOSD1
Driver Short-Circuit Current, VOUT = High (Note 4)
– 7V ≤ VOUT ≤ 10V
35
250
mA
IOSD2
Driver Short-Circuit Current, VOUT = Low (Note 4)
– 7V ≤ VOUT ≤ 10V
35
250
mA
IOS
RO and CD Short-Circuit Current
0V ≤ VOUT ≤ VCC
●
7
85
mA
IPULL-UP
CD Pull-Up Current
CD = 0V
●
15
60
µA
±30
12
mV
22
580
430
10
30
kΩ
900
700
µA
µA
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SWITCHING CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
tPLH
Driver Input to Output
RDIFF = 54Ω, CL1 = CL2 = 100pF
tPHL
Driver Input to Output
(Figures 4, 6)
●
10
28
60
ns
●
10
30
60
ns
tSKEW
Driver Output to Output
2
10
ns
tr, tf
Driver Rise or Fall Time
15
40
ns
tZH
Driver Enable to Output High
CL = 100pF (Figures 5, 7) S2 Closed
●
40
70
ns
tZL
Driver Enable to Output Low
CL = 100pF (Figures 5, 7) S1 Closed
●
40
100
ns
tLZ
Driver Disable Time from Low
CL = 15pF (Figures 5, 7) S1 Closed
●
40
70
ns
tHZ
Driver Disable Time from High
CL = 15pF (Figures 5, 7) S2 Closed
●
40
70
ns
tZH(SHDN)
Driver Enable from Shutdown to Output High
(Note 5)
CL = 100pF (Figures 5, 7) S2 Closed
●
40
100
ns
tZL(SHDN)
Driver Enable from Shutdown to Output Low
CL = 100pF (Figures 5, 7) S1 Closed
●
40
100
ns
tHZ(SHDN)
Driver Disable on Shutdown from Output High
CL = 15pF (Figures 5, 7) S2 Closed
●
40
100
ns
tLZ(SHDN)
Driver Disable on Shutdown from Output Low
CL = 15pF (Figures 5, 7) S1 Closed
●
40
100
ns
fMAX
Maximum Data Rate (Note 6)
●
4
5
tPLH
Receiver Input to Output (Note 7)
RDIFF = 54Ω, CL1 = CL2 = 100pF,
(Figures 4, 8)
●
30
138
200
ns
tPHL
Receiver Input to Output
RDIFF = 54Ω, CL1 = CL2 = 100pF,
(Figures 4, 8)
●
30
122
200
ns
tSKD
|tPLH – tPHL| Differential Receiver Skew
RDIFF = 54Ω, CL1 = CL2 = 100pF,
(Figures 4, 8)
tCDH
Receiver Input to CD Output High (Note 7)
RDIFF = 54Ω, CL1 = CL2 = 100pF,
(Figures 4, 10) DI/SHDN = VCC
●
2900
5000
ns
tCDL
Receiver Input to CD Output Low (Note 7)
RDIFF = 54Ω, CL1 = CL2 = 100pF,
(Figures 4, 10) DI/SHDN = VCC
●
150
300
ns
●
●
3
UNITS
Mbps
16
ns
3
LTC1482
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SWITCHING CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
tCDH(SHDN) Receiver Input to CD Output High at Shutdown
RDIFF = 54Ω, CL1 = CL2 = 100pF,
(Figures 4, 11) DI/SHDN = DE
●
2600
5000
ns
tCDL(SHDN) Receiver Input to CD Output Low from Shutdown
RDIFF = 54Ω, CL1 = CL2 = 100pF,
(Figures 4, 11) DI/SHDN = DE
●
2600
5000
ns
tZH(SHDN)
Receiver Enable from Shutdown to Output High
CL = 15pF (Figures 3, 9) S2 Closed,
A = 750mV, B = – 750mV, DE = 0,
DI/SHDN =
●
30
600
ns
tZL(SHDN)
Receiver Enable from Shutdown to Output Low
CL = 15pF (Figures 3, 9) S1 Closed,
A = – 750mV, B = 750mV, DE = 0,
DI/SHDN =
●
2600
5000
ns
tHZ(SHDN)
Receiver Disable from High on Shutdown
CL = 15pF (Figures 3, 9) S2 Closed,
A = 750mV, B = – 750mV, DE = 0,
DI/SHDN =
●
200
600
ns
tLZ(SHDN)
Receiver Disable from Low on Shutdown
CL = 15pF (Figures 3, 9) S1 Closed,
A = – 750mV, B = 750mV, DE = 0,
DI/SHDN =
●
200
600
ns
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 VCC = 5V and TA = 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.
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TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Threshold Voltage
(Output High) vs Temperature
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
6
RECEIVER OUTPUT VOLTAGE (V)
TA = 25°C
5
4
3
2
1
0
–0.2
VTHRO(LOW)
–0.16
VTHRO(HIGH)
–0.12
–0.08
–0.04
INPUT VOLTAGE (V)
0
1482 G01
4
0
–0.02
–0.04
VCM = 12V
VCC = 5V
VTHRO(HIGH)
–0.06
–0.08
–0.1
VCM = 0V
–0.12
VCM = –7V
–0.14
–0.16
–0.18
–0.20
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G02
Receiver Input Threshold Voltage
(Output Low) vs Temperature
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
Receiver Output Voltage vs Input
Voltage
0
VCC = 5V
VTHRO(LOW)
–0.02
–0.04
–0.06
–0.08
VCM = 12V
–0.1
–0.12
–0.14
–0.16
VCM = 0V
–0.18
–0.20
–55 –35 –15
VCM = –7V
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G03
LTC1482
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TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Offset Voltage vs
Temperature
Receiver Hysteresis vs
Temperature
80
–60
70
VCM = 12V
–100
VCM = 0V
–140
VCM = –7V
60
40
30
–160
20
–180
10
–200
–55 –35 –15
VCM = –7V TO 12V
50
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G04
CARRIER DETECT THRESHOLD VOLTAGE (V)
4.0
1.5
1.0
POSITIVE
VTHCD(LOW)
2.0
POSITIVE, VTHCD(HIGH)
NEGATIVE, VTHCD(HIGH)
3.5
NEGATIVE
VTHCD(LOW)
CARRIER DETECT OUTPUT VOLTAGE (V)
4.5
2.5
0.5
0
–0.25
–0.15
–0.05
0.05
0.15
RECEIVER INPUT VOLTAGE (V)
0.25
0.20
POSITIVE
VTHCD(HIGH)
0.15
VCM = 12V
0.10
VCM = –7V
0.05
NEGATIVE
VTHCD(HIGH)
0
VCM = 0V
VCM = 12V
–0.05
–0.10
VCM = 0V
–0.15
VCM = –7V
VCC = 5V
–0.20
–0.25
–55 –35 –15
–0.10
–0.14
–0.16
–0.18
4.3
4.2
4.1
4.0
3.9
3.8
3.7
3.6
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G10
4.5
4.75
5
5.25
SUPPLY VOLTAGE (V)
5.5
1482 G06
5 25 45 65 85 105 125
TEMPERATURE (°C)
0.25
VCM = 12V
POSITIVE
VTHCD(LOW)
0.20
0.15
VCM = –7V
0.10
VCM = 0V
0.05
0
NEGATIVE
VTHCD(LOW)
–0.05
–0.10
VCM = 12V
–0.15
VCC = 5V
–0.20
–0.25
–55 –35 –15
VCM = 0V
VCM = –7V
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G09
Receiver and Carrier Detect
Output Low Voltage vs Output
Current
5.0
4.5
40
VCC = 4.75V
TA = 25°C
TA = 25°C
VCC = 4.75
35
4.0
OUTPUT CURRENT (mA)
VCC = 4.75V
IOUT = –8mA
VTHRO(LOW)
–0.12
Carrier Detect Output High
Voltage vs Output Current
CARRIER DETECT OUTPUT HIGH VOLTAGE (V)
RECEIVER OUTPUT HIGH VOLTAGE (V)
4.5
VTHRO(HIGH)
–0.08
1482 G08
Receiver Output High Voltage vs
Temperature
3.5
–55 –35 –15
–0.06
Carrier Detect Threshold Voltage
(Output Low) vs Temperature
0.25
1482 G07
4.4
–0.04
Carrier Detect Threshold Voltage
(Output High) vs Temperature
5.0
TA = 25°C
1482 G05
Carrier Detect Output Voltage vs
Receiver Input Voltage
3.0
0
–0.02
–0.20
5 25 45 65 85 105 125
TEMPERATURE (°C)
CARRIER DETECT THRESHOLD VOLTAGE (V)
–80
–120
VCC = 5V
90
–40
RECEIVER INPUT THRESHOLD VOLTAGE (V)
100
VCC = 5V
–20
HYSTERESIS (mV)
RECEIVER INPUT OFFSET VOLTAGE (mV)
0
Receiver Input Threshold Voltage
vs Supply Voltage
3.5
3.0
2.5
2.0
1.5
30
25
20
15
10
1.0
5
0.5
0
–35
–30
–25 –20 –15 –10
OUTPUT CURRENT (µA)
–5
0
1482 G11
0
0
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
OUTPUT LOW VOLTAGE (V)
2
1482 G12
5
LTC1482
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TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Output High Voltage vs
Temperature
4.2
4.0
3.8
3.6
3.4
3.2
3.0
–55 –35 –15
3.95
VCC = 4.75V
IOUT = 10µA
3.90
3.85
3.80
3.75
VOH
3.70
3.65
3.60
3.50
–55 –35 –15
RECEIVER SKEW (ns)
RECEIVER PROPAGATION DELAY (ns)
25
tPHL
100
80
60
40
20
|tPLH – tPHL|
15
10
5
20
0
–55 –35 –15
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
80
50
40
30
20
OUTPUT HIGH
SHORT TO GROUND
0
–55 –35 –15
600
DRIVER ENABLED
NO LOAD
500
400
300
DRIVER DISABLED
100
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G19
6
700
THERMAL SHUTDOWN
WITH DRIVER
ENABLED
200
10
130
tPHL
120
110
4.5
4.75
5
5.25
SUPPLY VOLTAGE (V)
5.5
1482 G18
Logic Input Threshold vs
Temperature
2.00
VCC = 5V
800
SUPPLY CURRENT (µA)
RECEIVER SHORT-CIRCUIT CURRENT (mA)
900
OUTPUT LOW
SHORT TO VCC
tPLH
140
100
1000
60
TA = 25°C
Supply Current vs Temperature
VCC = 5.25V
70
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G17
Receiver Short-Circuit Current vs
Temperature
90
0.10
Receiver Propagation Delay vs
Supply Voltage
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G16
100
0.15
150
VCC = 5V
120
0.20
1482 G15
30
VCC = 5V
140
0.25
Receiver Skew vs Temperature
200
tPLH
0.30
1482 G14
Receiver Propagation Delay vs
Temperature
160
0.35
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G13
180
0.40
0.05
3.55
5 25 45 65 85 105 125
TEMPERATURE (°C)
VCC = 4.75V
IOUT = 8mA
0.45
RECEIVER PROPAGATION DELAY (ns)
OUTPUT VOLTAGE (V)
4.4
0.50
4.00
RECEIVER AND CARRIER
DETECT OUTPUT LOW VOLTAGE
VCC = 4.75V
I = 8mA
0
–55 –30 –5
20 45 70 95 120 145 170
TEMPERATURE (°C)
1482 G20
LOGIC INPUT THRESHOLD VOLTAGE (V)
4.6
CARRIER DETECT OUTPUT HIGH VOLTAGE (V)
4.8
Receiver and Carrier Detect
Output Low Voltage vs
Temperature
Carrier Detect Output High
Voltage vs Temperature
1.95
1.90
1.85
1.80
1.75
VCC = 5.25V
VCC = 5V
1.70
1.65
1.60
VCC = 4.75V
1.55
1.50
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G21
LTC1482
U W
TYPICAL PERFOR A CE CHARACTERISTICS
RL = 44Ω
2.5
1.5
VCC = 5V
VCC = 4.75V
VCC = 4.5V
1.0
0.5
∆VOD, VCC = 4.5V TO 5.25V
0
–0.5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
2.5
2.0
VCC = 5.25V
VCC = 5V
VCC = 4.75V
1.5
VCC = 4.5V
1.0
0.5
∆VOD, VCC = 4.5V TO 5.25V
0
–0.5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
Driver Common Mode Output
Voltage vs Temperature
VCC = 5.25V
VCC = 4.75V
1.5
VCC = 4.5V
1.0
0.5
∆VOC, VCC = 4.5V TO 5.25V
0
–55 –35 –15
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
VCC = 5V
2.0
VCC = 5.25V
VCC = 5V
VCC = 4.75V
1.5
VCC = 4.5V
1.0
0.5
∆VOC, VCC = 4.5V TO 5.25V
Driver Differential Output Voltage
vs Temperature
2.5
VCC = 5.25V
1.5
VCC = 5V
VCC = 4.75V
VCC = 4.5V
1.0
∆VOD3 FOR VCC = 4.5V TO 5.25V
0
–0.5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G28
VCC = 5V
VCC = 4.75V
VCC = 4.5V
1.5
1.0
0.5
∆VOD, VCC = 4.5V TO 5.25V
0
–0.5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
3.0
2.5
2.0
1.5
1.0
3.0
5 25 45 65 85 105 125
TEMPERATURE (°C)
Driver Differential Output Voltage
vs Temperature
3.0
0.5
2.5
1482 G26
VCM = –7V
VOD3
DI/SD HIGH
VCC = 5.25V
2.0
Driver Common Mode Output
Voltage vs Temperature
1482 G25
SEE FIGURE 2
2.5
1482 G24
RL = 54Ω
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
3.5
2.0
DRIVER COMMON MODE VOLTAGE (V)
2.0
3.0
RL = 44Ω
2.5
RL = 100Ω
3.0
Driver Common Mode Output
Voltage vs Temperature
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
DRIVER COMMON MODE VOLTAGE (V)
3.0
3.5
1482 G23
1482 G22
VCC = 5.25V
VCC = 5V
VCM = 12V
VOD3
DI/SD HIGH
SEE FIGURE 2
VCC = 4.75V
VCC = 4.5V
0.5
∆VOD3 FOR VCC = 4.5V TO 5.25V
0
–0.5
–55 –35 –15
DRIVER COMMON MODE VOLTAGE (V)
VCC = 5.25V
RL = 54Ω
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G29
RL = 100Ω
2.5
VCC = 5.25V
2.0
VCC = 5V
VCC = 4.75V
1.5
VCC = 4.5V
1.0
0.5
∆VOC, VCC = 4.5V TO 5.25V
0
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G27
Driver Differential Output Voltage
vs Output Current
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
2.0
3.0
Driver Differential Output Voltage
vs Temperature
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
3.0
Driver Differential Output Voltage
vs Temperature
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
Driver Differential Output Voltage
vs Temperature
5.0
VCC = 5V
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
1482 G30
7
LTC1482
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output High Voltage vs
Output Current
Driver Output Low Voltage vs
Output Current
3.0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–100 –90 –80 –70 –60 –50 –40 –30 –20 –10 0
OUTPUT CURRENT (mA)
40
VCC = 4.75V
DRIVER PROPAGATION DELAY (ns)
VCC = 4.75V
2.5
2.0
1.5
1.0
0.5
0
0
1482 G31
5.0
DRIVER PROPAGATION DELAY (ns)
DRIVER SKEW (ns)
tPHL
25
20
15
10
5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
5 25 45 65 85 105 125
TEMPERATURE (°C)
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G33
Driver Short-Circuit Current vs
Temperature
40
4.0
tPLH
30
Driver Propagation Delay vs
Supply Voltage
4.5
VCC = 5V
1482 G32
Driver Skew vs Temperature
0
–55 –35 –15
35
0
–55 –35 –15
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
250
TA = 25°C
35
DRIVER SHORT-CIRCUIT CURRENT (mA)
4.5
DRIVER OUTPUT LOW VOLTAGE (V)
DRIVER OUTPUT HIGH VOLTAGE (V)
5.0
Driver Propagation Delay vs
Temperature
tPHL
30
tPLH
25
20
15
10
5
0
4.5
4.75
5
5.25
SUPPLY VOLTAGE (V)
1482 G34
5.5
1482 G35
VCC = 5.25V
200
150
100
DRIVER OUTPUT HIGH
SHORT TO –7V
DRIVER OUTPUT LOW
SHORT TO 10V
50
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1482 G36
U
U
U
PIN FUNCTIONS
RO (Pin 1): Receiver Output. If a carrier is present (CD low)
and the part is not in shutdown, RO is high if the receiver
input differential voltage (A – B) ≥ VTHRO(MAX) and low if
(A – B) ≤ VTHRO(MIN). RO is forced to high (fail-safe state)
if a carrier is not present (CD = 1). In shutdown, RO is
three-stated. If the driver is enabled, RO follows the logic
level at the driver input.
CD (Pin 2): Open-Drain Carrier Detect Output. Provided
that the part is not in shutdown, the CD output is low if
VTHCD(MIN) ≥ (A – B) ≥ VTHCD(MAX) and high if VTHCD(MIN)
< (A – B) < VTHCD(MAX). This is true regardless of whether
the A and B pins are driven by the internal (DE = 1) or an
8
external (DE = 0) driver. A weak internal pull-up removes
the need for an external pull-up resistor if fast rise times
are not important. Several LTC1482s can share the same
CD line. CD = 1 forces RO to the high fail-safe state. In
shutdown, CD is three-stated. This pin can be pulled above
VCC but should not be taken above 8V to avoid damage.
DE (Pin 3): Driver Enable Input. DE = 0 disables or threestates the driver outputs. DE = 1 enables the driver outputs
with the high/low state of the outputs set by DI/SHDN.
DI/SHDN (Pin 4): Driver Input and Shutdown Input. It is
used together with the DE pin to put the part in shutdown
LTC1482
U
U
U
PIN FUNCTIONS
(DE = 0, DI/SHDN = 0) or to disable the driver while keeping
the receiver alive (DE = 0, DI/SHDN = 1). When the driver
is enabled (DE = 1), DI/SHDN = 0 forces the A output low
and the B output high. DI/SHDN = 1 forces the A output
high and the B output low.
When the driver is enabled, the A output follows the logic
level at the DI/SHDN pin.
GND (Pin 5): Ground.
B (Pin 7): Driver Output/Receiver Input. The input resistance is typically 22k when the driver is disabled (DE = 0).
When the driver is enabled, the B output is inverted from
the logic level at the DI/SHDN pin.
A (Pin 6): Driver Output/Receiver Input. The input resistance is typically 22k when the driver is disabled (DE = 0).
VCC (Pin 8): Positive Supply. 4.75V < VCC < 5.25V. A 0.1µF
bypass capacitor is recommended.
U
U
FU CTIO TABLES
Driver Disabled (DE = 0, Notes 1, 2)
Driver Enabled (DE = 1)
DI/SHDN
A
B
RO
CD
DI/SHDN
A–B
RO
CD
0
0
1
0
0
0
X (Note 3)
Z
1 (Internal Pull-Up)
1
1
0
1
0
1
VTHCD(MIN) < (A – B) < VTHCD(MAX)
1
1
1
1
A and B are Open
1
1
1
A and B are Shorted
1
1
1
VTHCD(MIN) ≥ (A – B) ≥ VTHCD(MAX)
and (A – B) ≤ VTHRO(MIN)
0
0
1
VTHCD(MIN) ≥ (A – B) ≥ VTHCD(MAX)
and (A – B) ≥ VTHRO(MAX)
1
0
X
A Shorted to B
1
Note 1: DE = 0, DI/SHDN = 0 puts the part in ICC shutdown and the supply
current drawn by the VCC pin drops to 20µA max. The receiver is always
alive except in shutdown.
Note 2: The table is valid regardless of the presence of an external
termination resistor.
Note 3: Although the RO and the driver outputs are three-stated, the A and
B pins each present a 22kΩ receiver input resistance to ground.
X = Don’t Care
Z = High Impedance
TEST CIRCUITS
375Ω
A
A
R
1k
VCC
VTST
–7V TO 12V
60Ω
VOD3
VOD
S1
TEST POINT
RECEIVER
OUTPUT
R
CL
VOC
1k
S2
375Ω
1482 F02
B
B
1482 F03
1482 F01
Figure 1. Driver DC Test Load #1
Figure 2. Driver DC Test Load #2
Figure 3. Receiver Timing Test Load
VCC
DE
1k
A
DI
CL1
B
CL2
S1
CD
RO
RDIFF
B
A
15pF
OUTPUT
UNDER TEST
VCC
500Ω
CL
S2
1482 F05
1482 F04
Figure 4. Driver/Receiver Timing Test Load
Figure 5. Driver Timing Test Load
9
LTC1482
U
W
W
SWITCHI G TI E WAVEFOR S
3V
f = 1MHz, tr ≤ 10ns, tf ≤ 10ns
1.5V
DI/SHDN
0V
1.5V
t PLH
t DSKEW
VO
90%
50%
10%
–VO
t PHL
VO = V(A) – V(B)
50%
tr
90%
10%
tf
B
VO
A
tSKEW
1/2 VO
t SKEW
1482 F06
NOTE: DE = 1
Figure 6. Driver Propagation Delays
3V
f = 1MHz, tr ≤ 10ns, tf ≤ 10ns
1.5V
DE
1.5V
0V
t ZL(SHDN), t ZL
5V
A, B
2.3V
VOL
VOH
A, B
t LZ, t LZ(SHDN)
OUTPUT NORMALLY LOW
500Ω PULL-UP TO VCC
0.5V
0.5V
OUTPUT NORMALLY HIGH,
500Ω PULL-DOWN TO GND
2.3V
0V
t HZ, t HZ(SHDN)
t ZH(SHDN), t ZH
1482 F07
NOTE: DI = 0 FOR tZL(SHDN), tLZ(SHDN); DI = DE FOR tZH(SHDN), tHZ(SHDN); DI = DE FOR tZL, tLZ; DI = VCC FOR tZH, tHZ
Figure 7. Driver Enable and Disable Timing
VOD2
A–B
– VOD2
0V
0V
INPUT
f = 1MHz, tr ≤ 10ns, tf ≤ 10ns
t PHL
t PLH
5V
RO
1.5V
1.5V
OUTPUT
VOL
1482 F08
NOTE: tSKD = |tPHL – tPLH|, DE = VCC
Figure 8. Receiver Propagation Delays
3V
f = 1MHz, tr ≤ 10ns, tf ≤ 10ns
1.5V
DI
5V
RO
t ZL(SHDN)
1.5V
1.5V
t LZ(SHDN)
OUTPUT
0V
0.5V
5V
RO
0.5V
OUTPUT
1.5V
0V
t ZH(SHDN)
NOTE: DE = 0, RO IS THREE-STATED IN SHUTDOWN, 1kΩ PULL-UP FOR NORMALLY LOW OUTPUT,
1kΩ PULL-DOWN FOR NORMALLY HIGH OUTPUT
Figure 9. Receiver Enable and Shutdown Timing
10
t HZ(SHDN)
1482 F09
LTC1482
U
W
W
SWITCHI G TI E WAVEFOR S
VOD2
A–B
– VOD2
0V
INPUT
t CDL
t CDH
VOH
1.5V
CD
VOL
1.5V
1482 F10
NOTE: 1kΩ PULL-UP AT CD
Figure 10. Carrier Detect Timing
5V
1.5V
DI
1.5V
0V
t CDH(SHDN)
t CDL(SHDN)
VOH
1.5V
CD
1.5V
VOL
VOD2
A–B
– VOD2
THREE-STATE
5V
RO
0V
1482 F11
NOTE: 1kΩ PULL-UP AT CD
Figure 11. Shutdown Carrier Detect Timing
11
LTC1482
U
W
U
U
APPLICATIONS INFORMATION
Carrier Detect Operation
The carrier detect or CD pin is an open-drain output with
a weak internal pull-up (30µA typical). This allows several
LTC1482s to share the same carrier detect line. The
internal pull-up has a series diode, permitting users to tie
the CD output to a voltage higher than VCC (8V max). When
driving low, the CD output can sink up to 4mA while
maintaining the output below a TTL VOL of 0.4V. An
external pull-up resistor is recommended if fast rise times
are important.
The LTC1482 defines the presence of a carrier as
VTHCD(MIN) ≥ (A – B) ≥ VTHCD(MAX). CD pulls low when a
carrier is present. When the carrier is absent, the weak
internal pull-up pulls CD high. For slow moving input
signals (below about 32kHz for signals conforming to
RS485 specifications), the CD output will go high when the
(A – B) signal is within the VTHCD(MIN) to VTHCD(MAX) range.
For faster input signals, the CD output does not glitch high
when the (A – B) signal is traversing the transition region.
This is achieved through internal delays in the CD signal
path. It takes tCDH (≤ 5µs) for CD to go high after the carrier
signal is removed. There are no additional built-in delays
for CD going low so that tCDL is only 300ns max.
When the LTC1482 is not in shutdown mode, CD = 1
always forces the receiver output (RO) high. If the driver
is enabled (DE = 1), CD = 0 as long as VTHCD min ≥ (A – B)
≥ VTHCD max. Shorting the A and B pins together or
excessive loading between these pins will cause this
condition to be violated and the CD pin will pull high. If the
driver is disabled, CD is guaranteed to go high when:
a) A is shorted to B,
b) A and B are open (with or without termination) or
c) VTHCD min ≤ A – B ≤ VTHCD max
The last condition occurs if the external driver is loaded
excessively.
In shutdown mode, RO is three-stated and CD is taken high
by the weak internal pull-up. On exiting shutdown, it takes
longer (tCDL(SHDN) = 5µs max) for CD to pull low when a
carrier is present.
12
When VCC is applied, some time is needed for CD and RO
to become valid. The time needed depends on the capacitance at the CD pin, the VCC rise time and the loads
connected to the A and B pins. For a load capacitance of
15pF and a 1µs VCC rise time, a wait time of 10µs is
recommended.
Receiver Output and Fail-Safe
If CD is low, the receiver output, RO, responds to the input
differential voltage and is guaranteed (by testing) to go
high if (A – B) ≥ VTHRO(MAX) and low if (A – B) ≤ VTHCD(MIN).
Some data encoding schemes require that the output of
the receiver maintain a known state (usually logic 1) when
data transmission ends and all drivers on the line are
forced into three-state. The carrier detect mechanism
ensures that RO will be high regardless of whether the line
is open, floating or shorted together, or whether the line is
terminated or not. This removes external components
required with earlier RS485 devices for the case where the
required known state is a logic 1. External components are
needed if the required state is a logic 0.
Fail-safe operates over the – 7V to 12V common mode
range and fast common mode steps do not affect the
receiver output.
Note that the CD output only goes high after all the drivers
are three-stated due to built-in delays (tCDH) in the CD
signal path (see Carrier Detect Operation). During the time
interval (see Figure 11) beginning at driver three-state and
ending at CD going high, the receiver output stays at the
last state just prior to the driver three-stating.
ICC Shutdown Mode
The supply current of the LTC1482 is reduced to 20µA max
by taking both the DE and DI/SHDN pins low. In shutdown,
all internal circuits are powered down and the driver and
receiver outputs are three-stated. The CD output is taken
high by the weak internal pull-up.
Logic within the LTC1482 prevents slow DE and DI/SHDN
transitions from generating internal shutdown pulses by
rejecting “shutdown pulses” of less than 50ns (typ) in
duration. Without this logic, the driver outputs will glitch
when three-stated momentarily.
LTC1482
U
W
U
U
APPLICATIONS INFORMATION
The supply current does not drop below 20µA immediately. DE and DI/SHDN must be low for a least 600ns
simultaneously for ICC to drop to half its operating value
(driver outputs unloaded) and for tCDH(SHDN) before dropping to the 20µA level. Taking either DE or DI/SHDN high
will wake the LTC1482 within 5µs.
In some applications, the A and B lines are pulled to VCC or
GND through external resistors to force the line to a high
or low state when all connected drivers are disabled. In
shutdown, the supply current will be higher than 10µA due
to the additional current drawn through the external pullup and the 22k input resistance of the LTC1482.
ESD Protection
The ESD performance of the LTC1482 A and B pins is
characterized to meet ±15kV using the Human Body
Model (100pF, 1.5kΩ), IEC-1000-4-2 Level 4 (±8kV)
contact mode and IEC-1000-4-2 Level 3 (±8kV) air discharge mode. This means that external voltage suppressors are not required in many applications, when compared with parts that are only protected to ±2kV. Pins
other than the A and B pins are protected to ±3kV typical
per the Human Body Model.
When powered up, the LTC1482 does not latch up or
sustain damage when the A and B pins are tested using any
of the three conditions listed. The data during the ESD
event may be corrupted, but after the event the LTC1482
continues to operate normally. The additional ESD protection at the A and B pins is important in applications where
these pins are exposed to the external world via connections to sockets.
Fault Protection
When shorted to – 7V or 10V at room temperature, the
short-circuit current in the driver pins is limited by internal
protection circuitry to 250mA. Over the industrial temperature range, the absolute maximum positive voltage at
any driver pin should be limited to 10V to avoid damage to
the part. At higher ambient temperatures, the rise in die
temperature, due to the short-circuit current, may trip the
thermal shutdown circuit. This circuit protects the part
against prolonged shorts at the driver outputs. If a driver
output is shorted to another output or to VCC , the current
will be limited to 250mA. If the die temperature rises above
150°C, the thermal shutdown circuit three-states the
driver outputs to open the current path. When the die cools
down to about 130°C, the driver outputs are taken out of
three-state. If the short persists, the part will heat again
and the cycle will repeat. This thermal oscillation occurs at
about 10Hz and protects the part from excessive power
dissipation. The average fault current drops as the driver
cycles between active and three-state. When the short is
removed, the part will return to normal operation.
When the driver is disabled, the receiver inputs can
withstand the entire – 7V to 12V RS485 common mode
range without damage.
13
LTC1482
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters), unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.118 ± 0.004*
(3.00 ± 0.102)
0.034 ± 0.004
(0.86 ± 0.102)
8
7 6
0° – 6° TYP
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
BSC
0.021 ± 0.006
(0.53 ± 0.015)
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1098
1
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
2 3
N8 Package
8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
0.255 ± 0.015*
(6.477 ± 0.381)
0.300 – 0.325
(7.620 – 8.255)
0.009 – 0.015
(0.229 – 0.381)
(
+0.035
0.325 –0.015
8.255
+0.889
–0.381
)
0.045 – 0.065
(1.143 – 1.651)
0.130 ± 0.005
(3.302 ± 0.127)
0.065
(1.651)
TYP
0.100
(2.54)
BSC
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
14
5
0.125
(3.175) 0.020
MIN (0.508)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
N8 1098
4
LTC1482
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters), unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SO8 1298
15
LTC1482
U
TYPICAL APPLICATIO
Fail-Safe “0” Application (Idle State = Logic “0”)
5V
I1
RO
CD
LTC1482
CD
R
DE
DE
DI
RO
I2
DI/
VCC
B
A
“A”
“B”
D
GND
SHDN
1482 TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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3.3V Ultralow Power RS485 Transceiver with Shutdown
Lower Supply Voltage
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Lowest Power
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LTC1484
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Low Power, High Output State When Inputs are Open,
Shorted or Terminated
LTC1485
5V RS485 Transceiver
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LTC1487
5V Ultralow Power RS485 with Low EMI, Shutdown and
High Input Impedance
Highest Input Impedance, Low EMI, Lowest Power
LTC1535
Isolated RS485 Transceiver
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LTC1685
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Propagation Delay Skew 500ps (Typ)
LTC1690
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LT1785
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±15kV ESD Protection, Industry Standard Pinout
16
Linear Technology Corporation
1482f LT/TP 0400 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 1998
工商网监
湘ICP备2023018690号
