LTC491CS#TRPBF [Linear]
LTC491 - Differential Driver and Receiver Pair; Package: SO; Pins: 14; Temperature Range: 0°C to 70°C;
| 型号： | LTC491CS#TRPBF |
| 厂家： | 
Linear |
| 描述： | LTC491 - Differential Driver and Receiver Pair; Package: SO; Pins: 14; Temperature Range: 0°C to 70°C 驱动 光电二极管 接口集成电路 驱动器 |
| 文件： | 总12页 (文件大小：184K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC491
Differential Driver and
Receiver Pair
U
FEATURES
DESCRIPTIO
The LTC®491 is a low power differential bus/line trans-
ceiverdesignedformultipointdatatransmissionstandard
RS485 applications with extended common mode range
(12V to –7V). It also meets the requirements of RS422.
■
Low Power: ICC = 300µA Typical
■
Designed for RS485 or RS422 Applications
■
Single 5V Supply
–7V to 12V Bus Common Mode Range
Permits ±7V Ground Difference Between Devices
on the Bus
Thermal Shutdown Protection
Power-Up/-Down Glitch-Free Driver Outputs Permit
Live Insertion or Removal of Package
Driver Maintains High Impedance in Three-State or
with the Power Off
Combined Impedance of a Driver Output and
Receiver Allows up to 32 Transceivers on the Bus
70mV Typical Input Hysteresis
28ns Typical Driver Propagation Delays with 5ns
Skew for 2.5MB Operation
Pin Compatible with the SN75180
■
TheCMOSdesignofferssignificantpowersavingsoverits
bipolarcounterpartwithoutsacrificingruggednessagainst
overload or ESD damage.
■
■
The driver and receiver feature three-state outputs, with
the driver outputs maintaining high impedance over the
entire 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.
■
■
■
■
Thereceiverhasafailsafefeaturewhichguaranteesahigh
output state when the inputs are left open.
■
■
Both AC and DC specifications are guaranteed from 0°C to
70°C and 4.75V to 5.25V supply voltage range.
Available in 14-LUead PDIP and SO Packages
APPLICATIO S
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
Low Power RS485/RS422 Transceiver
Level Translator
■
U
TYPICAL APPLICATIO
DE
4
DE
9
5
120Ω
120Ω
120Ω
D
R
DRIVER
RECEIVER
R
D
10
4000 FT 24 GAUGE TWISTED PAIR
4000 FT 24 GAUGE TWISTED PAIR
LTC491
LTC491
DRIVER
12
11
2
120Ω
RECEIVER
3
REB
REB
LTC491 • TA01
491fa
1
LTC491
W
U
W W W
U
/O
ABSOLUTE AXI U RATI GS
PACKAGE RDER I FOR ATIO
(Note 1)
Supply Voltage (VCC) ............................................... 12V
Control Input Voltages .................... –0.5V to VCC + 0.5V
Control Input Currents .......................... –50mA to 50mA
Driver Input Voltages ...................... –0.5V to VCC + 0.5V
Driver Input Currents ............................ –25mA to 25mA
Driver Output Voltages .......................................... ±14V
Receiver Input Voltages ......................................... ±14V
Receiver Output Voltages ............... –0.5V to VCC + 0.5V
Operating Temperature Range
LTC491C ................................................. 0°C to 70°C
LTC491I.............................................. –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
ORDER PART
NUMBER
NC
R
1
2
3
4
5
6
7
14
13
12
11
10
9
V
CC
R
NC
A
LTC491CN
LTC491CS
LTC491IN
LTC491IS
REB
DE
B
D
Z
D
Y
GND
GND
8
NC
N PACKAGE
S PACKAGE
14-LEAD PDIP
14-LEAD PLASTIC SO
TJMAX = 100°C, θJA = 90°C/W (N)
TJMAX = 100°C, θJA = 110°C/W (S)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5%
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
Differential Driver Output Voltage (Unloaded)
Differential Driver Output Voltage (With load)
I = 0
●
●
●
●
5
V
V
V
V
OD1
OD2
O
R = 50Ω; (RS422)
2
R = 27Ω; (RS485) (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
1.5
5
∆V
Change in Magnitude of Driver Differential Output
Voltage for Complementary Output States
0.2
OD
V
Driver Common Mode Output Voltage
●
●
3
V
V
OC
∆
V
Change in Magnitude of Driver Common Mode
Output Voltage for Complementary Output States
0.2
OC
V
V
Input High Voltage
Input Low Voltage
Input Current
D, DE, REB
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
2.0
V
V
IH
0.8
±2
IL
l
l
µA
mA
mA
V
IN1
IN2
Input Current (A, B)
V
CC
= 0V or 5.25V
V
= 12V
= –7V
1.0
IN
V
–0.8
0.2
IN
V
TH
Differential Input Threshold Voltage for Receiver
Receiver Input Hysteresis
–7V ≤V ≤12V
–0.2
3.5
CM
∆V
V
CM
= 0V
70
mV
V
TH
V
V
Receiver Output High Voltage
Receiver Output Low Voltage
Three-State Output Current at Receiver
Supply Current
I = –4mA, V = 0.2V
O ID
OH
I = 4mA, V = –0.2V
O
0.4
±1
V
OL
OZR
CC
ID
I
I
V
CC
= Max 0.4V ≤V ≤2.4V
µA
µA
µA
kΩ
mA
mA
mA
µA
O
No Load; D = GND, Outputs Enabled
or V
300
300
500
500
CC
Outputs Disabled
R
Receiver Input Resistance
–7V ≤V ≤12V
12
7
IN
CM
I
I
I
I
Driver Short Circuit Current, V
Driver Short Circuit Current, V
Receiver Short Circuit Current
= High
= Low
V = –7V
O
100
100
250
250
85
OSD1
OSD2
OSR
OZ
OUT
V = 12V
O
OUT
0V ≤V ≤V
O
CC
Driver Three-State Output Current
V = –7V to 12V
O
±2
±200
491fa
2
LTC491
U
The ● denotes the specifications which apply over the full operating
SWI I
TCH G CHARACTERISTICS
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5%
SYMBOL PARAMETER CONDITIONS
= 54Ω, C = C = 100pF
MIN
TYP
MAX
UNITS
t
Driver Input to Output
Driver Input to Output
R
●
●
10
30
50
50
ns
PLH
DIFF
L1
L2
(Figures 2, 5)
t
t
10
30
ns
PHL
Driver Output to Output
Driver Rise or Fall Time
●
●
5
15
ns
ns
SKEW
t , t
r
5
25
70
f
t
t
t
t
t
t
t
t
t
t
t
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time From Low
Driver Disable Time From High
Receiver Input to Output
C = 100pF (Figures 4, 6) S2 Closed
L
●
●
●
●
●
●
●
●
●
●
●
40
40
40
40
70
70
13
20
20
20
20
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ZH
ZL
LZ
HZ
C = 100pF (Figures 4, 6) S1 Closed
L
70
C = 15pF (Figures 4, 6) S1 Closed
L
70
C = 15pF (Figures 4, 6) S2 Closed
L
70
R
DIFF
= 54Ω, C = C = 100pF
40
40
150
150
PLH
PHL
SKD
ZL
L1
L2
(Figures 2, 7)
Receiver Input to Output
t
– t
PHL
Differential Receiver Skew
PLH
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable From Low
Receiver Disable From High
C = 15pF (Figures 3, 8) S1 Closed
L
50
50
50
50
C = 15pF (Figures 3, 8) S2 Closed
L
ZH
C = 15pF (Figures 3, 8) S1 Closed
L
LZ
C = 15pF (Figures 3, 8) S2 Closed
L
HZ
Note 1: Absolute Maximum Ratings are those values beyond which the life
Note 3: All typicals are given for V = 5V and temperature = 25°C.
CC
of the device may be impaired.
Note 2: 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.
U
U
U
PI FU CTIO S
NC (Pin 1): Not Connected.
GND (Pin 6): Ground Connection.
GND (Pin 7): Ground Connection.
NC (Pin 8): Not Connected.
Y (Pin 9): Driver Output.
R(Pin2):ReceiverOutput.Ifthereceiveroutputisenabled
(REB low), then if A > B by 200mV, R will be high. If A < B
by 200mV, then R will be low.
REB (Pin 3): Receiver Output Enable. A low enables the
receiver output, R. A high input forces the receiver output
into a high impedance state.
Z (Pin 10): Driver Output.
B (Pin 11): Receiver Input.
A (Pin 12): Receiver Input.
NC (Pin 13): Not Connected.
DE (Pin 4): Driver Output Enable. A high on DE enables the
driver outputs, Y and Z. A low input forces the driver
outputs into a high impedance state.
VCC (Pin 14): Positive Supply; 4.75V ≤ VCC ≤ 5.25V.
D (Pin 5): Driver Input. If the driver outputs are enabled
(DE high), then a low on D forces the driver outputs Y low
and Z high. A high on D will force Y high and Z low.
491fa
3
LTC491
TYPICAL PERFOR A CE CHARACTERISTICS
U W
Driver Output High Voltage
vs Output Current, TA = 25°C
Driver Differential Output Voltage
vs Output Current, TA = 25°C
Driver Output Low Voltage
vs Output Current, TA = 25°C
–96
–72
64
48
80
60
– 4 8
–24
0
32
16
0
40
20
0
0
0
0
1
2
3
4
1
2
3
4
1
2
3
4
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
LTC491 • TPC03
LTC491 • TPC01
LTC491 • TPC02
TTL Input Threshold vs Temperature
Driver Skew vs Temperature
Supply Current vs Temperature
1.63
1.61
1.59
1.57
1.55
5.0
4.0
3.0
2.0
1.0
350
340
330
320
310
–50
0
50
100
–50
0
50
100
–50
0
50
100
TEMPERATURE (°C )
TEMPERATURE (°C )
TEMPERATURE (°C )
LTC491 • TPC04
LTC491 • TPC05
LTC491 • TPC06
Driver Differential Output Voltage
vs Temperature, RO = 54Ω
Receiver tPLH PHL
t
Receiver Output Low Voltage
vs Temperature at I = 8mA
vs Temperature
2.3
2.1
1.9
1.7
1.5
7.0
6.0
5.0
4.0
3.0
0.8
0.6
0.4
0.2
0
–50
0
50
100
–50
0
50
100
–50
0
50
100
TEMPERATURE (°C )
TEMPERATURE (°C )
TEMPERATURE (°C )
LTC491 • TPC07
LTC491 • TPC08
LTC491 • TPC09
491fa
4
LTC491
TEST CIRCUITS
Y
Z
R
R
V
OD2
V
OC
LTC491 • F01
Figure 1. Driver DC Test Load
C
C
A
B
L1
Y
Z
R
DRIVER
RECEIVER
R
D
DIFF
L2
15pF
LTC491 • F02
Figure 2. Driver/Receiver Timing Test Circuit
S1
S2
1k
RECEIVER
OUTPUT
V
CC
1k
C
L
LTC491 • F03
Figure 3. Receiver Timing Test Load
S1
V
CC
500Ω
OUTPUT
UNDER TEST
C
L
S2
LTC491 • F04
Figure 4. Driver Timing Test Load
491fa
5
LTC491
U
W
W
SWITCHI G TI E WAVEFOR S
3V
f = 1MHz : t ≤ 10ns : t ≤ 10ns
D
1.5V
PLH
1.5V
PHL
r
f
0V
t
t
V
O
80%
90%
50%
10%
V
= V(Y) – V(Z)
50%
20%
DIFF
–V
O
t
t
f
r
Z
V
O
Y
LTC491 • F05
t
t
SKEW
1/2 V
1/2 V
O
SKEW
O
Figure 5. Driver Propagation Delays
3V
0V
5V
f = 1MHz : t ≤ 10ns : t ≤ 10ns
DE
A, B
A, B
1.5V
r
r
1.5V
LZ
t
t
ZL
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
2.3V
2.3V
0.5V
V
OL
OH
0V
V
0.5V
LTC491 • F06
t
t
ZH
HZ
Figure 6. Driver Enable and Disable Times
INPUT
V
OD2
f = 1MHz ; t ≤ 10ns : t ≤ 10ns
A-B
0V
0V
r
f
–V
OD2
t
t
PHL
PLH
V
OH
OUTPUT
R
1.5V
1.5V
V
OL
LTC491 • F07
Figure 7. Receiver Propagation Delays
3V
f = 1MHz : t ≤ 10ns : t ≤ 10ns
REB
R
1.5V
r
f
1.5V
0V
5V
t
t
LZ
ZL
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
1.5V
0.5V
V
OL
OH
0V
V
0.5V
R
1.5V
LTC491 • F08
t
t
ZH
HZ
Figure 8. Receiver Enable and Disable Times
491fa
6
LTC491
W U U
APPLICATIO S I FOR ATIO
U
Typical Application
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°Candturnsthembackonwhenthetemperaturecools
to 130°C. If the outputs of two or more LTC491 drivers are
shorted directly, the driver outputs can not supply enough
current to activate the thermal shutdown. Thus, the ther-
mal shutdown circuit will not prevent contention faults
when two drivers are active on the bus at the same time.
A typical connection of the LTC491 is shown in Figure 9.
Two twisted-pair wires connect up to 32 driver/receiver
pairs for full 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 imped-
ance, typically 120Ω. The input impedance of a receiver is
typically 20kΩ to GND, or 0.6 unit RS-485 load, so in
practice 50 to 60 transceivers can be connected to the
same wires. The optional shields around the twisted pair
help reduce unwanted noise, and are connected to GND at
one end.
12
2
3
120Ω
120Ω
RX
DX
RECEIVER
DATA IN
11
The LTC491 can also be used as a line repeater as shown
inFigure10. Ifthecablelengthislongerthan4000feet, the
LTC491 is inserted in the middle of the cable with the
receiver output connected back to the driver input.
4
10
9
5
DATA OUT
DRIVER
Thermal Shutdown
LTC491
LTC491 • F10
The LTC491 has a thermal shutdown feature which pro-
tects the part from excessive power dissipation. If the
Figure 10. Line Repeater
12
12
2
3
2
3
120Ω
120Ω
120Ω
RECEIVER
11
RX
DX
RX
RECEIVER
11
4
4
10
9
10
5
5
120Ω
DRIVER
DRIVER
DX
9
LTC491
LTC491
9
10
11
12
LTC491
RECEIVER
DRIVER
LTC491 • F09
5
4
3
2
DX
RX
Figure 9. Typical Connection
491fa
7
LTC491
PPLICATI
O U
W
U
A
S I FOR ATIO
Cables and Data Rate
When using low loss cables, Figure 12 can be used as a
guidelineforchoosingthemaximumlinelengthforagiven
datarate. WithlowerqualityPVCcables, thedielectricloss
factor can be 1000 times worse. PVC twisted pairs have
terrible losses at high data rates (>100kBs), and greatly
reduce the maximum cable length. At low data rates
however, theyareacceptableandmuchmoreeconomical.
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.
Losses in a transmission line are a complex combination
of DC conductor loss, AC losses (skin effect), leakage and
AC losses in the dielectric. In good polyethylene cables
such as the Belden 9841, the conductor losses and
dielectric losses are of the same order of magnitude,
leading to relatively low over all loss (Figure 11).
Cable Termination
The proper termination of the cable is very important.
If the cable is not terminated with it’s characteristic
impedance, distorted waveforms will result. In severe
cases, distorted (false) data and nulls will occur. A quick
look at the output of the driver will tell how well the cable
is terminated. It is best to look at a driver connected to the
end of the cable, since this eliminates the possibility of
getting reflections from two directions. Simply look at the
driver output while transmitting square wave data. If the
cable is terminated properly, the waveform will look like a
square wave (Figure 13).
10
1.0
If the cable is loaded excessively (47Ω), the signal initially
sees the surge impedance of the cable and jumps to an
initial amplitude. The signal travels down the cable and is
reflectedbackoutofphasebecauseofthemistermination.
0.1
0.1
1.0
10
100
PROBE HERE
FREQUENCY (MH )
Z
LTC491 • F11
Figure 11. Attenuation vs Frequency for Belden 9481
Rt
DX
DRIVER
RECEIVER
RX
10k
Rt = 120Ω
Rt = 47Ω
1k
100
10
Rt = 470Ω
10k
100k
1M 2.5M
10M
DATA RATE (bps)
LTC491 • F13
LTC491 • F12
Figure 12. Cable Length vs Data Rate
Figure 13. Termination Effects
491fa
8
LTC491
O U
W
U
PPLICATI
A
S I FOR ATIO
When the reflected signal returns to the driver, the ampli-
tude will be lowered. The width of the pedestal is equal to
twice the electrical length of the cable (about 1.5ns/foot).
If the cable is lightly loaded (470Ω), the signal reflects in
phase and increases the amplitude at the driver output. An
input frequency of 30kHz is adequate for tests out to 4000
feet of cable.
Receiver Open-Circuit Fail-Safe
Some data encoding schemes require that the output of
the receiver maintains a known state (usually a logic 1)
whenthedataisfinishedtransmittingandalldriversonthe
line are forced into three-state. The receiver of the LTC491
has a fail-safe feature which guarantees the output to be in
a logic 1 state when the receiver inputs are left floating
(open-circuit).However,whenthecableisterminatedwith
120Ω, the differential inputs to the receiver are shorted
together, not left floating. Because the receiver has about
70mV of hysteresis, the receiver output will tend to main-
tain the last data bit received, but this is not guaranteed.
AC Cable Termination
Cable termination resistors are necessary to prevent un-
wanted reflections, but they consume power. The typical
differential output voltage of the driver is 2V when the
cable is terminated with two 120Ω resistors, causing
33mA of DC current to flow in the cable when no data is
being sent. This DC current is about 60 times greater than
thesupplycurrentoftheLTC491. Onewaytoeliminatethe
unwanted current is by AC coupling the termination resis-
tors as shown in Figure 14.
The coupling capacitor must allow high-frequency energy
to flow to the termination, but block DC and low frequen-
cies. The dividing line between high and low frequency
depends on the length of the cable. The coupling capacitor
must pass frequencies above the point where the line
represents an electrical one-tenth wavelength. The value
of the coupling capacitor should therefore be set at 16.3pF
perfootofcablelengthfor120Ωcables. Withthecoupling
capacitors in place, power is consumed only on the signal
edges, and not when the driver output is idling at a 1 or 0
state. A 100nF capacitor is adequate for lines up to 4000
feet in length. Be aware that the power savings start to
decrease once the data rate surpasses 1/(120Ω × C).
The termination resistors are used to generate a DC bias
which forces the receiver output to a known state; in the
case of Figure 15, a logic 0. The first method consumes
about 208mW and the second about 8mW. The lowest
power solution is to use an AC termination with a pull-up
resistor. Simply swap the receiver inputs for data proto-
cols ending in logic 1.
5V
110Ω
110Ω
130Ω
130Ω
RECEIVER
RX
5V
1.5k
140Ω
RECEIVER
RX
1.5kΩ
120Ω
100kΩ
120Ω
5V
C
C
RECEIVER
RX
RECEIVER
RX
C = LINE LENGTH (ft) x 16.3pF
LTC491 • F15
LTC491 • F14
Figure 14. AC Coupled Termination
Figure 15. Forcing “O” When All Drivers are Off
491fa
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LTC491
PPLICATI
O U
W
U
A
S I FOR ATIO
Fault Protection
Y
All of LTC’s RS485 products are protected against ESD
transients up to 2kV using the human body model (100pF,
1.5kΩ). However, some applications need more
protection. The best protection method is to connect a
bidirectional TransZorb® from each line side pin to ground
(Figure 16).
120Ω
DRIVER
Z
LTC491 • F16
Figure 16. ESD Protection with TransZorbs
A TransZorb is a silicon transient voltage suppressor that
has exceptional surge handling capabilities, fast response
time, and low series resistance. They are available from
GeneralSemiconductorIndustriesandcomeinavarietyof
breakdown voltages and prices. Be sure to pick a break-
down voltage higher than the common mode voltage
required for your application (typically 12V). Also, don’t
forget to check how much the added parasitic capacitance
will load down the bus.
TransZorb is a registered trademark of General Instruments, GSI
U
PACKAGE DESCRIPTIO
N Package
14-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.770*
(19.558)
MAX
14
13
12
11
10
9
8
7
.255 ± .015*
(6.477 ± 0.381)
1
2
3
5
6
4
.300 – .325
(7.620 – 8.255)
.045 – .065
(1.143 – 1.651)
.130 ± .005
(3.302 ± 0.127)
.020
(0.508)
MIN
.065
(1.651)
TYP
.008 – .015
(0.203 – 0.381)
+.035
.325
.005
(0.125)
MIN
–.015
.120
(3.048)
MIN
.018 ± .003
(0.457 ± 0.076)
.100
(2.54)
BSC
+0.889
8.255
(
)
–0.381
NOTE:
INCHES
MILLIMETERS
N14 1002
1. DIMENSIONS ARE
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
491fa
10
LTC491
U
PACKAGE DESCRIPTIO
S Package
14-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.337 – .344
.045 ±.005
(8.560 – 8.738)
.050 BSC
N
NOTE 3
13
12
11
10
8
14
N
9
.245
MIN
.160 ±.005
.150 – .157
.228 – .244
(5.791 – 6.197)
(3.810 – 3.988)
NOTE 3
1
2
3
N/2
N/2
7
.030 ±.005
TYP
RECOMMENDED SOLDER PAD LAYOUT
1
2
3
4
5
6
.010 – .020
(0.254 – 0.508)
× 45°
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
.008 – .010
(0.203 – 0.254)
0° – 8° TYP
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
.016 – .050
(0.406 – 1.270)
S14 0502
NOTE:
1. DIMENSIONS IN
INCHES
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
491fa
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
LTC491
U
TYPICAL APPLICATIO S
RS232 Receiver
RS232 to RS485 Level Transistor with Hysteresis
R = 220k
RS232 IN
Y
5.6k
RX
RECEIVER
1/2 LTC491
10k
120Ω
RS232 IN
DRIVER
1/2 LTC491
HYSTERESIS = 10kΩ •
5.6k
LTC491 • TA02
Z
VY - VZ
19k
———— ————
≈
R
R
LTC491 • TA03
RELATED PARTS
PART NUMBER
LTC486/LTC487
LTC488/LTC489
LTC1480
DESCRIPTION
COMMENTS
Low Power Quad RS485 Drivers
110µA Supply Current
7mA Supply Current
Lower Supply Voltage
Lowest Power
Low Power Quad RS485 Receivers
3.3V Supply RS485 Transceiver
LTC1481
Low Power RS485 Transceiver with Shutdown
RS485 Transceiver with Carrier Detect
Low Power, Low EMI RS485 Transceiver
RS485 Transceiver with Fail-Safe
10Mbps RS485 Transceiver
LTC1482
±15kV ESD, Fail-Safe
LTC1483
Slew Rate Limited Driver Outputs, Lowest Power
±15kV ESD, MSOP Package
LTC1484
LTC1485
High Speed
LTC1518/LTC1519
LTC1520
52Mbps Quad RS485 Receivers
Higher Speed, LTC488/LTC489 Pin-Compatible
100mV Threshold, Low Channel-to-Channel Skew
LVDS-Compatible Quad Receiver
2500V Isolated RS485 Transceiver
52Mbps RS485 Transceiver
LTC1535
Full-Duplex, Self-Powered Using External Transformer
Industry-Standard Pinout, 500ps Propagation Delay Skew
LTC490/LTC491 Pin Compatible
LTC1685
LTC1686/LTC1687
LTC1688/LTC1689
LTC1690
52Mbps Full-Duplex RS485 Transceiver
100Mbps Quad RS485 Drivers
Highest Speed, LTC486/LTC487 Pin Compatible
±15kV ESD, LTC490 Pin Compatible
Full-Duplex RS485 Transceiver with Fail-Safe
±60V Protected RS485 Transceivers
±60V Protected Full-Duplex RS485 Transceivers
LT1785/LTC1785A
LT1791/LTC1791A
±15kV ESD, Fail-Safe (LT1785A)
±15kV ESD, Fail-Safe (LT1791A), LTC491 Pin Compatible
491fa
LT/TP 0104 1K REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
LINEAR TECHNOLOGY CORPORATION 1992
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
相关型号：
LTC491IS#TR
LTC491 - Differential Driver and Receiver Pair; Package: SO; Pins: 14; Temperature Range: -40°C to 85°C
Linear
LTC491IS#TRPBF
LTC491 - Differential Driver and Receiver Pair; Package: SO; Pins: 14; Temperature Range: -40°C to 85°C
Linear
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