LTC487
Quad Low Power
RS485 Driver
FeaTures
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DescripTion
The LTC
®
487 is a low power differential bus/line driver
designed for multipoint data transmission standard RS485
applications with extended common mode range (– 7V to
12V). It also meets RS422 requirements.
The CMOS design offers significant power savings over
its bipolar counterpart without sacrificing ruggedness
against overload or ESD damage.
The driver features three-state outputs, with the driver
outputs maintaining high impedance over the entire com-
mon 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.
Both AC and DC specifications are guaranteed from 0°C to
70°C (Commercial), –40°C to 85°C (Industrial) and over
the 4.75V to 5.25V supply voltage range.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
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Very Low Power: I
CC
= 110µA Typ
Designed for RS485 or RS422 Applications
Single 5V Supply
– 7V to 12V Bus Common Mode Range Permits ±7V
GND Difference Between Devices on the Bus
Thermal Shutdown Protection
Power-Up/Down Glitch-Free Driver Outputs Permit
Live Insertion/Removal of Package
Driver Maintains High Impedance in Three-State or
with the Power Off
28ns Typical Driver Propagation Delays with
5ns Skew
Pin Compatible with the SN75174, DS96174,
µA96174, and DS96F174
applicaTions
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Low Power RS485/RS422 Drivers
Level Translator
Typical applicaTion
RS485 Cable Length Specification*
10k
EN 12
4
2
DI
1
DRIVER
3
1/4 LTC487
LTC487 TA01
EN 12
4
2
120
4000 FT BELDEN 9841
120
1
RECEIVER
3
RO
CABLE LENGTH (FT)
1k
1/4 LTC489
100
10
10k
100k
1M
2.5M
10M
DATA RATE (bps)
LTC487 TA09
* APPLIES FOR 24 GAUGE, POLYETHYLENE
DIELECTRIC TWISTED PAIR
487fc
LTC487
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
DI1
DO1A
DO1B
EN12
Supply Voltage (V
CC
) ................................................12V
Control Input Voltages .................... –0.5V to V
CC
+ 0.5V
Driver Input Voltages ...................... –0.5V to V
CC
+ 0.5V
Driver Output Voltages ............................................ ±14V
Control Input Currents .........................................±25mA
Driver Input Currents ...........................................±25mA
Operating Temperature Range
Commercial ............................................. 0°C to 70°C
Industrial .............................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.).................. 300°C
1
2
3
4
5
6
7
8
16
V
CC
15
DI4
14
DO4A
13
DO4B
12
EN34
11
DO3B
10
DO3A
9
DI3
DO2B
DO2A
DI2
GND
N PACKAGE
SW PACKAGE
16-LEAD PLASTIC DIP
16-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 70°C/W (N)
T
JMAX
= 150°C,
θ
JA
= 95°C/W (S)
Consult factory for Military grade parts.
orDer inForMaTion
LEAD FREE FINISH
LTC487CN#PBF
LTC487CSW#PBF
LTC487IN#PBF
LTC487ISW#PBF
TAPE AND REEL
LTC487CN#TRPBF
LTC487CSW#TRPBF
LTC487IN#TRPBF
LTC487IS#TRPBF
PART MARKING
LTC487CN
LTC487CSW
LTC487IN
LTC487ISW
PACKAGE DESCRIPTION
16-Lead Plastic DIP
16-Lead Plastic SO
16-Lead Plastic DIP
16-Lead Plastic SO
TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
487fc
LTC487
Dc elecTrical characTerisTics
(Industrial) (Notes 2, 3)
SYMBOL
V
OD1
V
OD2
V
OD
V
OC
V
OC
V
CC
= 5V ± 5%, 0°C ≤ T
A
≤ 70°C (Commercial), –40°C ≤ T
A
≤ 85°C
MIN
2
1.5
5
0.2
3
0.2
TYP
MAX
5
UNITS
V
V
V
V
V
V
PARAMETER
Differential Driver Output Voltage (Unloaded)
Differential Driver Output Voltage (With Load)
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
Supply Current
Driver Short-Circuit Current, V
OUT
= High
Driver Short-Circuit Current, V
OUT
= Low
High Impedance State Output Current
CONDITIONS
I
O
= 0
R = 50Ω; (RS422)
R = 27Ω; (RS485) (Figure 3)
R = 27Ω or R = 50Ω
(Figure 3)
V
IH
V
IL
I
IN1
I
CC
I
OSD1
I
OSD2
I
OZ
DI, EN12, EN34
2.0
V
0.8
±2
V
µA
µA
µA
mA
mA
µA
No Load
V
O
= – 7V
V
O
= 12V
Output Enabled
Output Enabled
110
110
100
100
±10
200
200
250
250
±200
V
O
= –7V to 12V
swiTching characTerisTics
SYMBOL
t
PLH
t
PHL
t
SKEW
t
r,
t
f
t
ZH
t
ZL
t
LZ
t
HZ
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
V
CC
= 5V
±
5%, 0°C
≤
T
A
≤
70°C (Notes 2, 3)
MIN
10
10
5
TYP
30
30
5
20
35
35
35
35
MAX
50
50
15
25
70
70
70
70
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
CONDITIONS
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
(Figures 1, 4)
C
L
= 100pF (Figures 2, 5) S2 Closed
C
L
= 100pF (Figures 2, 5) S1 Closed
C
L
= 15pF (Figures 2, 5) S1 Closed
C
L
= 15pF (Figures 2, 5) S2 Closed
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All currents into device pins are positive; all currents out of
device pins are negative. All voltages are referenced to device GND unless
otherwise specified.
Note 3:
All typicals are given for V
CC
= 5V and Temperature = 25°C.
487fc
LTC487
Typical perForMance characTerisTics
Driver Output High Voltage
vs Output Current
–96
OUTPUT CURRENT (mA)
T
A
= 25°C
64
OUTPUT CURRENT (mA)
Driver Differential Output Voltage
vs Output Current
T
A
= 25°C
80
OUTPUT CURRENT (mA)
Driver Output Low Voltage
vs Output Current
T
A
= 25°C
–72
48
60
–48
32
40
–24
16
20
0
0
1
2
3
4
487 G01
0
0
1
2
3
4
487 G02
0
0
1
2
3
4
487 G03
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
TTL Input Threshold
vs Temperature
1.63
INPUT THRESHOLD VOLTAGE (V)
5.0
Driver Skew vs Temperature
130
SUPPLY CURRENT (µA)
Supply Current vs Temperature
1.61
TIME (ns)
4.0
120
1.59
3.0
110
1.57
2.0
100
1.55
–50
0
50
100
487 G04
1.0
–50
0
50
100
487 G05
90
–50
0
50
100
487 G06
TEMPERATURE (°C )
TEMPERATURE (°C )
TEMPERATURE (°C )
Driver Differential Output Voltage
vs Temperature
2.3
DIFFERENTIAL VOLTAGE (V)
R
O
= 54
2.1
1.9
1.7
1.5
–50
0
50
100
487 G07
TEMPERATURE (°C )
487fc
LTC487
pin FuncTions
DI1 (Pin 1):
Driver 1 Input. If Driver 1 is enabled, then a
low on DI1 forces the driver outputs DO1A low and DO1B
high. A high on DI1 with the driver outputs enabled will
force DO1A high and DO1B low.
DO1A (Pin 2):
Driver 1 Output.
DO1B (Pin 3):
Driver 1 Output.
EN12 (Pin 4):
Driver 1 and 2 Outputs Enabled. See Func-
tion Table for details.
DO2B (Pin 5):
Driver 2 Output.
DO2A (Pin 6):
Driver 2 Output.
DI2 (Pin 7):
Driver 2 Input. Refer to DI1.
GND (Pin 8):
GND Connection.
DI3 (Pin 9):
Driver 3 Input. Refer to DI1.
DO3A (Pin 10):
Driver 3 Output.
DO3B (Pin 11):
Driver 3 Output.
EN34 (Pin 12):
Driver 3 and 4 Outputs Enabled. See Func-
tion Table for details.
DO4B (Pin 13):
Driver 4 Output.
DO4A (Pin 14):
Driver 4 Output.
DI4 (Pin 15):
Driver 4 Input. Refer to DI1.
V
CC
(Pin 16):
Positive Supply; 4.75 < V
CC
< 5.25.
FuncTion Table
INPUT
DI
H
L
X
ENABLES
EN12 or EN34
H
H
L
OUT A
H
L
Z
OUTPUTS
OUT B
L
H
Z
H: High Level
L: Low Level
X: Irrelevant
Z: High Impedance (Off)
swiTching TiMe waveForMs
DI
3V
1.5V
0V
B
A
V
O
–V
O
V
O
1/2 V
O
80%
10%
t
r
t
SKEW
V
DIFF
= V(A) – V(B)
1/2 V
O
90%
20%
t
f
LTC487 • TA05
f = 1MHz : t
r
< 10ns : t
f
< 10ns
1.5V
t
PHL
t
PLH
t
SKEW
Figure 1. Driver Propagation Delays
EN12
3V
1.5V
0V
5V
A, B
V
OL
V
OH
A, B
0V
t
ZH
t
ZL
2.3V
OUTPUT NORMALLY LOW
f = 1MHz : t
r
≤ 10ns : t
f
≤ 10ns
1.5V
t
LZ
0.5V
0.5V
t
HZ
2.3V
OUTPUT NORMALLY HIGH
LTC487 • TA06
Figure 2. Driver Enable and Disable Times
487fc
传感器
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