LTC1484
Low Power
RS485 Transceiver
with Receiver Fail-Safe
FEATURES
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
s
No Damage or Latchup to
±
15kV ESD (Human
Body Model), IEC-1000-4-2 Level 4 Contact (
±
8kV)
and Level 3 (
±
8kV) Air Gap Specifications
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 for Driver Enable with No 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
Power Up/Down Glitch-Free Driver Outputs
Up to 32 Transceivers on the Bus
Pin Compatible with the LTC485
Available in 8-Lead
MSOP,
PDIP and SO Packages
The LTC
®
1484 is a low power RS485 compatible trans-
ceiver. In receiver mode, it offers a fail-safe feature which
guarantees a high receiver output state when the inputs
are left open, shorted together or terminated with no
signal present. No external components are required to
ensure the high receiver output state.
Both driver and receiver feature three-state outputs with
separate receiver and driver control pins. The driver
outputs maintain high impedance over the entire com-
mon mode range when three-stated. Excessive power
dissipation caused by bus contention or faults is pre-
vented by a thermal shutdown circuit that forces the
driver outputs into a high impedance state.
Enhanced ESD protection allows the LTC1484 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 LTC1484 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.
APPLICATIO S
s
s
s
Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
TYPICAL APPLICATIO
RS485 Interface
LTC1484
RO1
RE1
DE1
D
DI1
GND1
GND2
1484 TA01
LTC1484
V
CC1
V
CC2
B2
120Ω
120Ω
A2
D
R
RO2
RE2
DE2
DI2
B1
A1
Dl1
R
B2
A2
RO2
Dl1
↑↓
Dl2 = 0
RE1 = RE2 = 0
U
Driving a 2000 Foot STP Cable
DE1 = V
CC
DE2 = 0
1484 TA01a
U
U
1
LTC1484
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
Supply Voltage (V
CC
)............................................... 6.5V
Control Input Voltages ................. – 0.3V to (V
CC
+ 0.3V)
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
RE
DE
DI
1
2
3
4
8
7
6
5
V
CC
B
A
GND
TOP VIEW
RO 1
RE 2
DE 3
D
DI 4
R
8
7
6
5
V
CC
B
A
GND
LTC1484CMS8
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 200°C/ W
MS8 PART MARKING
LTDX
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
OD1
V
OD2
PARAMETER
Differential Driver Output Voltage (Unloaded)
Differential Driver Output Voltage (with Load)
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
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, RE
DE, DI, RE
DE, DI, RE
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
V
OD3
∆V
OD
V
OC
∆|V
OC
|
V
IH
V
IL
I
IN1
I
IN2
V
TH
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)
Differential Input Threshold Voltage for Receiver
2
U
U
W
W W
U
W
Junction Temperature .......................................... 125°C
Operating Temperature Range
LTC1484C ......................................... 0°C
≤
T
A
≤
70°C
LTC1484I ...................................... – 40°C
≤
T
A
≤
85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1484CN8
LTC1484CS8
LTC1484IN8
LTC1484IS8
S8 PART MARKING
1484
1484I
N8 PACKAGE
8-LEAD PDIP
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
0.8
±2
1.0
– 0.8
– 0.20
– 0.015
V
µA
mA
mA
V
LTC1484
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
TH
V
OH
V
OL
I
OZR
R
IN
I
CC
I
SHDN
I
OSD1
I
OSD2
I
OSR
PARAMETER
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
Driver Short-Circuit Current, V
OUT
= High (Note 4)
Driver Short-Circuit Current, V
OUT
= Low (Note 4)
Receiver Short-Circuit Current
CONDITIONS
V
CM
= 0V, DE = 0
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,
DE = 0
–7V
≤
V
CM
≤
12V
No Load, Output Enabled (DE = V
CC
)
No Load, Output Disabled (DE = 0)
DE = 0, RE = V
CC
, DI = 0
– 7V
≤
V
OUT
≤
10V
– 7V
≤
V
OUT
≤
10V
0V
≤
V
OUT
≤
V
CC
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
3.5
TYP
±30
MAX
UNITS
mV
V
0.4
±1
12
22
600
400
1
35
35
7
900
700
20
250
250
85
V
µA
kΩ
µA
µA
µA
mA
mA
mA
SWITCHING CHARACTERISTICS
SYMBOL
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
t
DZR
f
MAX
t
SHDN
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
Receiver Input to Output
Receiver Input to Output
|t
PLH
– t
PHL
| Differential Receiver Skew
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable from Low
Receiver Disable from High
Driver Enable to Receiver Valid
Maximum Data Rate (Note 5)
Time to Shutdown (Note 6)
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
CONDITIONS
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
(Figures 4, 6)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
(Figures 4, 6)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
(Figures 4, 6)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
(Figures 4, 6)
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
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)
C
RL
= 15pF (Figures 3, 9) S1 Closed
C
RL
= 15pF (Figures 3, 9) S2 Closed
C
RL
= 15pF (Figures 3, 9) S1 Closed
C
RL
= 15pF (Figures 3, 9) S2 Closed
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
(Figures 4, 10)
DE = 0, RE↑
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
U
MIN
10
10
TYP
28.5
31
2.5
MAX
60
60
10
40
70
100
70
70
200
200
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
3
15
40
40
40
40
30
30
160
140
20
20
20
20
20
1600
50
50
50
50
3000
ns
ns
ns
ns
ns
Mbps
4
50
5
300
600
ns
3
LTC1484
SWITCHING CHARACTERISTICS
SYMBOL
t
ZH(SHDN)
t
ZL(SHDN)
t
ZH(SHDN)
t
ZL(SHDN)
PARAMETER
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
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
C
L
= 100pF (Figures 5, 7) S2 Closed,
DI = DE
C
L
= 100pF (Figures 5, 7) S1 Closed,
DI = 0
C
L
= 15pF (Figures 3, 9) S2 Closed,
DE = 0
C
L
= 15pF (Figures 3, 9) S1 Closed,
DE = 0
q
q
q
q
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.
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Output Voltage vs Input
Voltage
RECEIVER INPUT THRESHOLD VOLTAGE (V)
6
RECEIVER OUTPUT VOLTAGE (V)
5
4
3
2
1
0
–0.2
T
A
= 25°C
V
CC
= 5V
0
V
CC
= 5V
V
TH(HIGH)
–0.05
V
CM
= –7V
–0.10
V
CM
= 0V
–0.15
V
CM
= 12V
RECEIVER INPUT THRESHOLD VOLTAGE (V)
V
TH(LOW)
–0.16
V
TH(HIGH)
0
1484 G01
–0.12
–0.08
–0.04
INPUT VOLTAGE (V)
4
U W
U
MIN
TYP
40
40
MAX
100
100
10
10
UNITS
ns
ns
µs
µs
Note 5:
Guaranteed by design.
Note 6:
Time for I
CC
to drop to I
CC
/2 when the receiver is disabled.
Receiver Input Threshold Voltage
(Output High) vs Temperature
0
Receiver Input Threshold Voltage
(Output Low) vs Temperature
V
CC
= 5V
V
TH(LOW)
–0.05
–0.10
–0.15
V
CM
= 0V
–0.20
V
CM
= –7V
–0.20
V
CM
= 12V
–0.25
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G02
–0.25
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G03
LTC1484
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Offset Voltage vs
Temperature
0
RECEIVER INPUT OFFSET VOLTAGE (mV)
–20
–40
–60
–80
–100
–120
–140
–160
–180
V
CC
= 5V
RECEIVER HYSTERESIS (mV)
90
80
70
60
50
40
30
20
10
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G04
V
CC
= 5V
RECEIVER INPUT THRESHOLD VOLTAGE (V)
V
CM
= –7V
V
CM
= 0V
V
CM
= 12V
–200
–55 –35 –15
Receiver Output High Voltage vs
Output Current
5.0
RECEIVER OUTPUT HIGH VOLTAGE (V)
RECEIVER OUTPUT LOW VOLTAGE (V)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–25
–20
–15
–10
–5
OUTPUT CURRENT (mA)
0
1484 G07
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
5
10
15
20
OUTPUT CURRENT (mA)
25
1484 G08
RECEIVER OUTPUT HIGH VOLTAGE (V)
V
CC
= 4.75V
Receiver Output Low Voltage vs
Temperature
0.50
RECEIVER OUTPUT LOW VOLTAGE (V)
V
CM
= 12V
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G10
400
INPUT CURRENT (µA)
RECEIVER INPUT RESISTANCE (kΩ)
0.45
V
CC
= 4.75V
I
OUT
= 8mA
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
CM
= 0V
V
TH(HIGH)
V
TH(HIGH)
– V
TH(LOW)
V
CM
= –7V TO 12V
V
TH(LOW)
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G05
4.5
4.75
5
SUPPLY VOLTAGE (V)
5.25
1484 G06
Receiver Output Low Voltage vs
Output Current
1.0
0.9
V
CC
= 4.75V
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
3.6
Receiver Output High Voltage vs
Temperature
V
CC
= 4.75V
I
OUT
= –8mA
3.5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G09
Input Current (A, B) vs
Temperature
600
500
26.0
25.5
25.0
24.5
Receiver Input Resistance vs
Temperature
V
CC
= 0V OR 5V
300
200
100
0
–100
–200
–300
–400
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G11
V
CM
= 12V
V
CM
= –7V
V
CC
= 0V OR 5V
24.0
23.5
23.0
22.5
22.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1484 G12
V
CM
= –7V
5
MEMS传感器
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