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LTC487ISW#PBF

P1-P3P4-P6P7-P9P10-P12
LTC487
4
487fc
Typical perForMance characTerisTics
TTL Input Threshold
vs Temperature
Driver Skew vs Temperature Supply Current vs Temperature
Driver Differential Output Voltage
vs Temperature
Driver Output High Voltage
vs Output Current
Driver Differential Output Voltage
vs Output Current
Driver Output Low Voltage
vs Output Current
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (mA)
0
–24
– 48
–72
–96
1 2 3 4
487 G01
T
A
= 25°C
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (mA)
0
16
32
48
64
1 2 3 4
487 G02
T
A
= 25°C
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (mA)
0
20
40
60
80
1 2 3 4
487 G03
T
A
= 25°C
TEMPERATURE (°C )
–50
INPUT THRESHOLD VOLTAGE (V)
1.55
1.57
1.59
1.61
1.63
0 50 100
487 G04
TEMPERATURE (°C )
–50
TIME (ns)
1.0
2.0
3.0
4.0
5.0
0 50 100
487 G05
TEMPERATURE (°C )
–50
SUPPLY CURRENT (µA)
90
100
110
120
130
0 50 100
487 G06
TEMPERATURE (°C )
–50
DIFFERENTIAL VOLTAGE (V)
1.5
1.7
1.9
2.1
2.3
0 50 100
487 G07
R
O
= 54Ω
LTC487
5
487fc
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.
H: High Level
L: Low Level
X: Irrelevant
Z: High Impedance (Off)
INPUT ENABLES OUTPUTS
DI EN12 or EN34 OUT A OUT B
H
L
X
H
H
L
H
L
Z
L
H
Z
FuncTion Table
swiTching TiMe waveForMs
LTC487 • TA06
A, B
EN12
3V
0V
f = 1MHz : t 10ns : t 10ns
V
OL
V
OH
1.5V 1.5V
5V
OUTPUT NORMALLY LOW
t
ZL
2.3V
t
LZ
0.5V
≤ ≤
A, B
0V
t
ZH
2.3V
OUTPUT NORMALLY HIGH
t
HZ
0.5V
r f
Figure 2. Driver Enable and Disable Times
Figure 1. Driver Propagation Delays
LTC487
6
487fc
TesT circuiT
applicaTions inForMaTion
LTC487 TA02
A
B
R
R
OD
V
OC
V
DRIVER 1
LTC487 TA03
DI
A
B
EN12
R
DIFF
C
L1
C
L2
LTC487 TA04
OUTPUT
UNDER TEST
C
L
S1
500
CC
V
Ω
S2
Figure 5. Driver Timing Test Load #2Figure 4. Driver Timing Test CircuitFigure 3. Driver DC Test Load
Typical Application
A typical connection of the LTC487 is shown in Figure 6.
A twisted pair of wires connect up to 32 drivers and
receivers for half duplex data transmission. There are
no restrictions on where the chips are connected to the
wires, and it isn’t necessary to have the chips connected
at the ends. However, the wires must be terminated only at
the ends with a resistor equal to their characteristic im-
pedance, typically 120Ω. The optional shields around the
twisted pair help reduce unwanted noise, and are connected
to GND at one end.
Thermal Shutdown
The LTC487 has a thermal shutdown feature which protects
the part from excessive power dissipation. If the outputs
of the driver are accidently shorted to a power supply or
low impedance source, up to 250mA can flow through
the part. The thermal shutdown circuit disables the driver
outputs when the internal temperature reaches 150°C and
turns them back on when the temperature cools to 130°C.
If the outputs of two or more LTC487 drivers are shorted
directly, the driver outputs can not supply enough cur-
rent to activate the thermal shutdown. Thus, the thermal
shutdown circuit will not prevent contention faults when
two drivers are active on the bus at the same time.
Cable and Data Rate
The transmission line of choice for RS485 applications is
a twisted pair. There are coaxial cables (twinaxial) made
for this purpose that contain straight pairs, but these are
less flexible, more bulky, and more costly than twisted
pairs. Many cable manufacturers offer a broad range of
120Ω cables designed for RS485 applications.
EN12
4
LTC487 • TA07
120Ω
DX
1
2
3
SHIELD
120Ω
RX
RX
SHIELD
3
DX
EN12
4
2
EN12
4
1
2
3
RX
RX
3
DX
EN12
4
1
DX
1/4 LTC4891/4 LTC487
1/4 LTC4891/4 LTC487
2
1
Figure 6. Typical Connection
P1-P3P4-P6P7-P9P10-P12

LTC487ISW#PBF

Mfr. #:
Buy LTC487ISW#PBF
Manufacturer:
Analog Devices Inc.
Description:
RS-485 Interface IC 4x L Pwr RS485 Drvr
Lifecycle:
New from this manufacturer.
Delivery:
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