LTC489ISWPBF [Linear]
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| 型号： | LTC489ISWPBF |
| 厂家： | 
Linear |
| 描述： | 暂无描述 |
| 文件： | 总12页 (文件大小：232K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC488/LTC489
Quad RS485 Line Receiver
U
EATURE
S
F
DESCRIPTIO
■
■
■
■
Low Power: ICC = 7mA Typ
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
60mV Typical Input Hysteresis
Receiver Maintains High Impedance in Three-State or
with the Power Off
The LTC®488 and LTC489 are low power differential bus/
line receivers designed for multipoint data transmission
standardRS485applicationswithextendedcommonmode
range (12V to –7V). They also meet the requirements of
RS422.
■
■
TheCMOSdesignofferssignificantpowersavingsoverits
bipolarcounterpartwithoutsacrificingruggednessagainst
overload or ESD damage.
■
■
■
28ns Typical Receiver Propagation Delay
Pin Compatible with the SN75173 (LTC488)
Pin Compatible with the SN75175 (LTC489)
Thereceiverfeaturesthree-stateoutputs,withthereceiver
output maintaining high impedance over the entire com-
mon mode range.
O U
The receiver has a fail-safe feature which guarantees a
high output state when the inputs are left open.
PPLICATI
S
A
■
Low Power RS485/RS422 Receivers
Level Translator
Both AC and DC specifications are guaranteed 4.75V to
5.25V supply voltage range.
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
O
TYPICAL APPLICATI
EN
EN
EN
EN
4
2
1
12
DRIVER
1/4 LTC486
RECEIVER
1/4 LTC488
3
120Ω
120Ω
RO
DI
4000 FT 24 GAUGE TWISTED PAIR
EN12
EN12
4
2
1
DRIVER
1/4 LTC487
RECEIVER
1/4 LTC489
3
120Ω
120Ω
RO
DI
4000 FT 24 GAUGE TWISTED PAIR
LTC488/9 TA01
1
LTC488/LTC489
W W W
U
(Note 1)
ABSOLUTE AXI U RATI GS
Supply Voltage (VCC) .............................................. 12V
Control Input Currents ........................ – 25mA to 25mA
Control Input Voltages ................ – 0.5V to (VCC + 0.5V)
Receiver Input Voltages ........................................ ±14V
Receiver Output Voltages ........... – 0.5V to (VCC + 0.5V)
Operating Temperature Range
LTC488C/LTC489C ................................. 0°C to 70°C
LTC488I/LTC489I .............................. – 40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
W
U
/O
PACKAGE RDER I FOR ATIO
TOP VIEW
TOP VIEW
ORDER PART
ORDER PART
1
2
3
4
5
6
7
8
V
CC
16
15
14
13
12
11
10
9
B1
A1
1
2
3
4
5
6
7
8
V
CC
16
15
14
13
12
11
10
9
NUMBER
B1
A1
NUMBER
R
R
R
R
B4
B4
R
R
R
A4
RO1
EN
A4
RO1
EN12
RO2
A2
LTC489CN
LTC489CS
LTC489IN
LTC489IS
LTC488CN
LTC488CS
LTC488IN
LTC488IS
RO4
EN
RO4
EN34
RO3
A3
RO2
A2
RO3
A3
B2
B2
R
B3
GND
B3
GND
S PACKAGE
16-LEAD PLASTIC SOL
N PACKAGE
16-LEAD PLASTIC DIP
S PACKAGE
16-LEAD PLASTIC SOL
N PACKAGE
16-LEAD PLASTIC DIP
TJMAX = 150°C, θJA = 70°C/W (N PKG)
TJMAX = 150°C, θJA = 90°C/W (S PKG)
TJMAX = 150°C, θJA = 70°C/W (N PKG)
TJMAX = 150°C, θJA = 90°C/W (S PKG)
Consult factory for Military grade parts.
DC LECTRICAL CHARACTERISTICS VCC = 5V (Notes 2, 3), unless otherwise noted.
E
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
Input High Voltage
Input Low Voltage
Input Current
EN, EN, EN12, EN34
EN, EN, EN12, EN34
EN, EN, EN12, EN34
●
●
●
2.0
V
V
INH
INL
IN1
IN2
0.8
I
I
±2
µA
Input Current (A, B)
V
CC
V
CC
= 0V or 5.25V, V = 12V
= 0V or 5.25V, V = – 7V
●
●
1.0
– 0.8
mA
mA
IN
IN
V
Differential Input Threshold Voltage for Receiver
Receiver Input Hysteresis
–7V ≤ V ≤ 12V
●
– 0.2
3.5
0.2
V
mV
V
TH
CM
∆V
V
CM
= 0V
60
7
TH
V
V
Receiver Output High Voltage
Receiver Output Low Voltage
Three-State Output Current at Receiver
Supply Current
I = – 4mA, V = 0.2V
●
●
●
●
●
●
●
●
OH
O
ID
I = 4mA, V = – 0.2V
0.4
±1
V
OL
OZR
CC
O
ID
I
I
V
CC
= Max 0.4V ≤ V ≤ 2.4V
µA
mA
kΩ
mA
ns
O
No Load, Digital Pins = GND or V
10
CC
R
Receiver Input Resistance
–7V ≤ V ≤ 12V, V = 0V
12
7
IN
CM
CC
I
t
t
t
Receiver Short-Circuit Current
Receiver Input to Output
0V ≤ V ≤ V
CC
85
55
55
OSR
PLH
PHL
SKD
O
C = 15pF (Figures 1, 3)
L
12
12
28
28
4
Receiver Input to Output
C = 15pF (Figures 1, 3)
L
ns
| t
– t
|
C = 15pF (Figures 1, 3)
L
ns
PLH
PHL
Differential Receiver Skew
2
LTC488/LTC489
V
CC = 5V ± 5% (Notes 2, 3), unless otherwise noted.
DC ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
30
MAX
60
UNITS
ns
t
t
t
t
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable from Low
Receiver Disable from High
C = 15pF (Figures 2, 4) S1 Closed
●
●
●
●
ZL
ZH
LZ
HZ
L
C = 15pF (Figures 2, 4) S2 Closed
30
60
ns
L
C = 15pF (Figures 2, 4) S1 Closed
30
60
ns
L
C = 15pF (Figures 2, 4) S2 Closed
30
60
ns
L
The
range.
●
denotes specifications that apply over the operating temperature
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.
Note 1: Absolute Maximum Ratings are those beyond which the safety of
the device may be impaired.
Note 3: All typicals are given for V = 5V and T = 25°C.
CC
A
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Output High Voltage vs
Temperature at I = 8mA
Receiver Output Low Voltage vs
Temperature at I = 8mA
4.8
4.6
4.4
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
4.2
4.0
3.8
3.6
3.4
3.2
3.0
0
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75 100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
488 G02
488 G01
Receiver Output Low Voltage vs
Output Current at TA = 25°C
Receiver Output High Voltage vs
Output Current at TA = 25°C
36
32
28
24
20
–18
–16
–14
–12
–10
16
12
8
–8
–6
–4
–2
4
0
0
0
0.5
1.5
OUTPUT VOLTAGE (V)
1.0
2.0
5
4
3
2
OUTPUT VOLTAGE (V)
488 G04
488 G03
3
LTC488/LTC489
TYPICAL PERFOR A CE CHARACTERISTICS
U W
TTL Input Threshold vs
Temperature
Receiver |tPLH – tPHL| vs
Supply Current vs Temperature
Temperature
1.63
1.61
1.59
1.57
5
4
3
2
7.0
6.6
6.2
5.8
1.55
1
5.4
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75 100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
488 G05
488 G06
488 G07
U
U
U
PI FU CTIO S
B 1 (Pin 1) Receiver 1 Input.
A1 (Pin 2) Receiver 1 Input.
B3 (Pin 9) Receiver 3 Input.
A3 (Pin 10) Receiver 3 Input.
RO3 (Pin 11) Receiver 3 Output. Refer to RO1.
EN (Pin 12)(LTC488) Receiver Output Disabled. See
Function Table for details.
EN34 (Pin 12)(LTC489) Receiver 3, Receiver 4 output
enabled. See Function Table for details.
RO4 (Pin 13) Receiver 4 Output. Refer to RO1.
A4 (Pin 14) Receiver 4 Input.
B4 (Pin 15) Receiver 4 Input.
RO1 (Pin 3) Receiver 1 Output. If the receiver output is
enabled, then if A > B by 200mV, RO1 will be high. If
A < B by 200mV, then RO1 will be low.
EN (Pin 4) (LTC488) Receiver Output Enabled. See
Function Table for details.
EN12 (Pin 4) (LTC489) Receiver 1, Receiver 2 Output
Enabled. See Function Table for details.
RO2 (Pin 5) Receiver 2 Output. Refer to RO1.
A2 (Pin 6) Receiver 2 Input.
B2 (Pin 7) Receiver 2 Input.
V
CC (Pin 16) Positive Supply; 4.75V ≤ VCC ≤ 5.25V.
GND (Pin 8) Ground Connection.
4
LTC488/LTC489
U
U
FU CTIO TABLES
LTC489
LTC488
DIFFERENTIAL
ENABLES
OUTPUT
DIFFERENTIAL
ENABLES
OUTPUT
A – B
EN12 or EN34
RO
H
?
A – B
EN
EN
RO
V
ID
≥ 0.2V
H
H
H
L
V
≥ 0.2V
H
X
X
L
H
H
ID
–0.2V < V < 0.2V
ID
–0.2V < V < 0.2V
H
X
X
L
?
?
ID
V
X
≤ 0.2V
L
ID
Z
V
X
≤ 0.2V
H
X
X
L
L
L
ID
H: High Level
L: Low Level
X: Irrelevant
?: Indeterminate
Z: High Impedance (Off)
L
H
Z
TEST CIRCUITS
100pF
A
D
RO
DRIVER
RECEIVER
54Ω
C
L
B
100pF
488/9 F01
Figure 1. Receiver Timing Test Circuit
Note: The input pulse is supplied by a generator having the following characteristics:
f = 1MHz, Duty Cycle = 50%, t < 10ns, t ≤ 10ns, Z = 50Ω
r
f
OUT
S1
S2
1k
RECEIVER
OUTPUT
V
CC
C
L
1k
488/9 F02
Figure 2. Receiver Enable and Disable Timing Test Circuit
5
LTC488/LTC489
U
W
W
SWITCHI G TI E WAVEFOR S
INPUT
f = 1MHz; t ≤ 10ns; t ≤ 10ns
V
OD2
r
f
INPUT
A, B
0V
t
0V
–V
OD2
t
PHL
PLH
V
OH
RO
1.5V
1.5V
V
OL
488/9 F03
Figure 3. Receiver Propagation Delays
3V
0V
f = 1MHz; t ≤ 10ns; t ≤ 10ns
r
f
EN OR
EN12
1.5V
1.5V
t
ZL
t
LZ
5V
RO
1.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
0.5V
V
OL
t
ZH
t
HZ
V
OH
0.5V
RO
1.5V
0V
488/9 F04
Figure 4. Receiver Enable and Disable Times
O U
W
U
PPLICATI
A
S I FOR ATIO
Cables and Data Rate
Typical Application
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.
A typical connection of the LTC488/LTC489 is shown in
Figure 5. Two twisted-pair wires connect up to 32 driver/
receiver pairs 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
impedance, typically 120Ω. The input impedance of a
receiver is typically 20k to GND, or 0.5 unit RS485 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.
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 cable
such as the Belden 9841, the conductor losses and dielec-
tric losses are of the same order of magnitude, leading to
relatively low overall loss (Figure 6).
6
LTC488/LTC489
O U
S
W
U
PPLICATI
A
I FOR ATIO
EN
4
SHIELD
SHIELD
2
3
RX
DX
1/4 LTC486
1
3
1/4 LTC488 OR
1/4 LTC489
DX
120Ω
120Ω
RX
1
12
1
2
EN
1/4 LTC488 OR
1/4 LTC489
RX
3
2
12
DX
1/4 LTC486
4
488/9 F05
EN
EN
3
1
DX
RX
Figure 5. Typical Connection
10
10k
1k
1
100
10
0.1
0.1
1
10
100
2.5M
10k
100k
1M
10M
FREQUENCY (MHz)
DATA RATE (bps)
488/9 F06
488/9 F07
Figure 6. Attenuation vs Frequency for Belden 9841
Figure 7. Cable Length vs Data Rate
When using low loss cables, Figure 7 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 (> 100kbps), and greatly
reduce the maximum cable length. At low data rates
however, theyareacceptableandmuchmoreeconomical.
Cable Termination
Theproperterminationofthecableisveryimportant.Ifthe
cable is not terminated with its 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
7
LTC488/LTC489
O U
W
U
PPLICATI
A
S I FOR ATIO
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 8).
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
the supply current of the LTC488/LTC489. One way to
eliminate the unwanted current is by AC coupling the
termination resistors as shown in Figure 9.
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.
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 drive output. An
input frequency of 30kHz is adequate for tests out to 4000
ft. of cable.
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
perfootofcablelengthfor120Ω cables. 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).
PROBE HERE
Rt
DRIVER
RECEIVER
DX
RX
Rt = 120Ω
120Ω
Rt = 47Ω
RECEIVER
RX
C
488/9 F09
C = LINE LENGTH (FT)(16.3pF)
Rt = 470Ω
488/9 F08
Figure 9. AC Coupled Termination
Figure 8. Termination Effects
8
LTC488/LTC489
O U
W
U
PPLICATI
A
S I FOR ATIO
Receiver Open-Circuit Fail-Safe
The termination resistors are used to generate a DC bias
which forces the receiver output to a known state, in this
case 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 pullup resistor. Simply
swap the receiver inputs for data protocols ending in
logic 1.
Some data encoding schemes require that the output of
the receiver maintains a known state (usually a logic 1)
whenthedataisfinishedtransmittingandalldriversonthe
line are forced in three-state. The receiver of the LTC488/
LTC489 has a fail-safe feature which guarantees the out-
put to be in a logic 1 state when the receiver inputs are left
floating (open-circuit). When the input is terminated with
120Ω and the receiver output must be forced to a known
state, the circuits of Figure 10 can be used.
Fault Protection
All of LTC’s RS485 products are protected against ESD
transients up to 2kV using the human body model (100pF,
1.5k). However, some applications need more protection.
The best protection method is to connect a bidirectional
TransZorb® from each line side pin to ground (Figure 11).
5V
110Ω
130Ω
130Ω
110Ω
RECEIVER
RX
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
General instruments, GSI, and come in a variety of break-
down voltages and prices. Be sure to pick a breakdown
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.
5V
1.5k
120Ω
RECEIVER
RX
1.5k
Y
5V
DRIVER
120Ω
100k
Z
C
RECEIVER
RX
120Ω
488/9 F11
488/9 F10
Figure 11. ESD Protection with TransZorbs®
Figure 10. Forcing “0” When All Drivers Are Off
TransZorb is a registered trademark of General Instruments, GSI
9
LTC488/LTC489
U
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTIO
N Package
16-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.770*
(19.558)
MAX
14
12
10
9
8
15
13
11
16
0.255 ± 0.015*
(6.477 ± 0.381)
2
1
3
4
6
5
7
0.300 – 0.325
0.130 ± 0.005
0.045 – 0.065
(7.620 – 8.255)
(3.302 ± 0.127)
(1.143 – 1.651)
0.020
(0.508)
MIN
0.065
(1.651)
TYP
0.009 – 0.015
(0.229 – 0.381)
+0.035
–0.015
0.325
0.125
(3.175)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
0.100 ± 0.010
(2.540 ± 0.254)
+0.889
8.255
(
)
–0.381
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
N16 1197
10
LTC488/LTC489
U
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTIO
SW Package
16-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
0.398 – 0.413*
(10.109 – 10.490)
15 14 12
10
11
9
16
13
0.394 – 0.419
(10.007 – 10.643)
NOTE 1
2
3
5
7
8
1
4
6
0.291 – 0.299**
(7.391 – 7.595)
0.037 – 0.045
(0.940 – 1.143)
0.093 – 0.104
(2.362 – 2.642)
0.010 – 0.029
(0.254 – 0.737)
× 45°
0° – 8° TYP
0.050
(1.270)
TYP
0.004 – 0.012
(0.102 – 0.305)
0.009 – 0.013
NOTE 1
(0.229 – 0.330)
0.014 – 0.019
0.016 – 0.050
(0.356 – 0.482)
TYP
(0.406 – 1.270)
NOTE:
1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
S16 (WIDE) 0396
*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
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
LTC488/LTC489
U
TYPICAL APPLICATION
RS232 Receiver
RS232
IN
RECEIVER
1/4 LTC488 OR
1/4 LTC489
RX
5.6k
LTC488/9 TA02
RELATED PARTS
PART NUMBER
LTC485
DESCRIPTION
COMMENTS
Low Power RS485 Transceiver
Low Power, Half-Duplex
Full-Duplex in SO-8
LTC490
Low Power RS485 Full-Duplex Transceiver
3V, Ultralow Power RS485 Transceiver
3V, Ultralow Power RS485 Transceiver
Ultralow Power RS485 Low EMI Transceiver
Fast RS485 Transceiver
LTC1480
LTC1481
LTC1483
LTC1485
LTC1487
LTC1685
1µA Shutdown Mode
Lowest Power on 5V Supply
Low EMI/Low Power with Shutdown
10Mbps Operation
Ultralow Power RS485 with Low EMI and High Input Impedance
High Speed RS485 Transceiver
Up to 256 Nodes on a Bus
52Mbps, Pin Compatible with LTC485
52Mbps, Pin Compatible LTC490/LTC491
LTC1686/LTC1687 High Speed RS485 Full-Duplex Transceiver
4889fa LT/TP 0898 REV A 2K • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 1992
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LTC490 - Differential Driver and Receiver Pair; Package: SO; Pins: 8; Temperature Range: 0°C to 70°C
Linear
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