LT1785ACS8#TRPBF [Linear]
暂无描述;
| 型号： | LT1785ACS8#TRPBF |
| 厂家： | 
Linear |
| 描述： | 暂无描述 驱动 光电二极管 接口集成电路 驱动器 |
| 文件： | 总18页 (文件大小：338K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1785/LT1785A/
LT1791/LT1791A
60V Fault Protected
RS485/RS422 Transceivers
FEATURES
DESCRIPTION
TheLT®1785/LT1791arehalf-duplexandfull-duplexdiffer-
ential bus transceivers for RS485 and RS422 applications
which feature on-chip protection from overvoltage faults
on the data transmission lines. Receiver input and driver
output pins can withstand voltage faults up to ±±60 with
respect to ground with no damage to the device. Faults
may occur while the transceiver is active, shut down or
powered off.
n
Protected from Overvoltage Line Faults to ±±0ꢀ
n
Pin Compatible with LTC485 and LTC491
n
High Input Impedance Supports Up to 128 Nodes
No Damage or Latchup to ESD
n
n
IEC-1666-4-2 Level 4: ±15k0 Air Discharge
n
IEC-1666-4-2 Level 2: ±4k0 Contact Discharge
n
Controlled Slew Rates for EMI Emissions Control
n
Guaranteed High Receiver Output State for Floating,
Shorted or Inactive Inputs (LT1785A/LT1791A)
Data rates to 256kbaud on networks of up to 128 nodes
are supported. Controlled slew rates on the driver out-
putscontrol EMI emissions and improve data transmis-
sion integrity on improperly terminated lines. Drivers are
specified to operate with inexpensive cables as low as
72Ω characteristic impedance.
n
Outputs Assume a High Impedance When Off or
Powered Down
n
Drives Low Cost, Low Impedance Cables
n
Short-Circuit Protection on All Outputs
n
Thermal Shutdown Protection
Guaranteed Operation to 125°C
n
n
The LT1785A/LT1791A devices have “fail-safe” receiver
inputstoguaranteeareceiveroutputhighforshorted,open
or inactive data lines. On-chip ESD protection eliminates
need for external protection devices.
AEC-Q166 Qualified for Automotive Applications
(LT1785#W)
APPLICATIONS
The LT1785/LT1785A are available in 8-lead DIP and SO
packages and the LT1791/LT1791A in 14-lead DIP and
SO packages.
n
Industrial Control Data Networks
n
CAN Bus Applications
n
H0AC Controls
All registered trademarks and trademarks are the property of their respective owners.
TYPICAL APPLICATION
Normal Operation Waveforms at 250kBaud
ꢑ
ꢒꢒꢃ
Rꢎꢃ
Rꢓ
REꢃ
Rꢀ
R
ꢅꢆRꢇ
ꢐꢅꢃꢈꢉꢊ
ꢂꢆꢃ
ꢂꢏꢃ
ꢅꢓ
ꢌꢍꢎ
ꢀꢁꢂꢃ
ꢑ
ꢊꢋ
ꢒꢒꢄ
Rꢎꢄ
Rꢓ
REꢄ
R
ꢅꢆRꢇ
ꢐꢅꢃꢈꢉꢊ
ꢁꢂꢃꢄꢅꢁ ꢆꢇꢈꢉ
ꢂꢆꢄ
ꢂꢏꢄ
ꢅꢓ
ꢀꢁꢂꢄ
ꢃꢈꢉꢊꢋꢃ ꢅꢌꢍꢃ
Rev. F
1
Document Feedback
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
(Note 1)
ABSOLUTE MAXIMUM RATINGS
Supply 0oltage (0 ) ................................................180
Operating Temperature Range
CC
Receiver Enable Input 0oltage...................... –6.30 to ±0
Driver Enable Input 0oltage.......................... –6.30 to ±0
Driver Input 0oltage................................... –6.30 to 180
Receiver Input 0oltage................................ –±60 to ±60
Driver Output 0oltage.................................. –±60 to ±60
LT1785C/LT1791C/
LT1785AC/LT1791AC.................................... 6°C to 76°C
LT1785I/LT1791I/
LT1785AI/LT1791AI.................................. –46°C to 85°C
LT1785H/LT1791H/
LT1785AH/LT1791AH.............................–46°C to 125°C
Storage Temperature Range...................–±5°C to 156°C
Lead Temperature (Soldering, 16 sec) .................. 366°C
Receiver Output 0oltage...................–6.30 to (0 + ±0)
CC
PIN CONFIGURATION
ꢀꢁꢂ ꢃꢄꢅꢆ
ꢈꢉꢊ ꢋꢌꢍꢎ
ꢇꢉ
Rꢁ
ꢌ
ꢒ
ꢓ
ꢍ
ꢔ
ꢕ
ꢖ
ꢌꢍ
ꢌꢓ
ꢌꢒ
ꢌꢌ
ꢌꢗ
ꢘ
ꢃ
ꢉꢉ
R
ꢇꢉ
ꢈ
Rꢉ
RE
ꢔꢍ
ꢔꢌ
ꢀ
ꢁ
ꢂ
ꢃ
ꢋ
ꢐ
ꢑ
ꢄ
ꢅ
ꢆ
ꢇ
ꢏꢏ
R
RE
ꢐꢅ
ꢚ
ꢔ
ꢐꢄ
ꢛ
ꢒꢓꢔ
ꢐ
ꢋꢇꢐ
ꢋꢇꢐ
ꢜ
ꢓꢄ ꢊꢑꢏꢕꢑꢒꢍ
ꢄꢖꢗꢍꢑꢔ ꢊꢔꢌꢊ
ꢘꢄ ꢊꢑꢏꢕꢑꢒꢍ
ꢄꢖꢗꢍꢑꢔ ꢊꢗꢑꢘꢈꢌꢏ ꢘꢉ
ꢙ
ꢇꢉ
T
= 156°C, θ = 136°C/W (N8)
JMAX
JA
ꢇ ꢂꢈꢉꢊꢈꢋꢅ
ꢑ ꢂꢈꢉꢊꢈꢋꢅ
T
= 156°C, θ = 156°C/W (S8)
ꢌꢍꢎꢏꢅꢈꢐ ꢂꢐꢄꢂ ꢌꢍꢎꢏꢅꢈꢐ ꢂꢏꢈꢑꢀꢄꢉ ꢑꢁ
JMAX
JA
T
= 156°C, θ = 136°C/W (N)
JA
JMAX
T
= 156°C, θ = 156°C/W (S)
JMAX
JA
ORDER INFORMATION
LEAD FREE FINISH
LT1785CN8#PBF
LT1785CS8#PBF
LT1785IN8#PBF
LT1785IS8#PBF
LT1785ACN8#PBF
LT1785ACS8#PBF
LT1785AIN8#PBF
LT1785AIS8#PBF
LT1785HN8#PBF
LT1785HS8#PBF
LT1785AHN8#PBF
LT1785AHS8#PBF
LT1791CN#PBF
TAPE AND REEL
PART MARKING*
1785
PACKAGE DESCRIPTION
8-Lead PDIP
TEMPERATURE RANGE
6°C to 76°C
LT1785CN8#TRPBF
LT1785CS8#TRPBF
LT1785IN8#TRPBF
LT1785IS8#TRPBF
LT1785ACN8#TRPBF
LT1785ACS8#TRPBF
LT1785AIN8#TRPBF
LT1785AIS8#TRPBF
LT1785HN8#TRPBF
LT1785HS8#TRPBF
LT1785AHN8#TRPBF
LT1785AHS8#TRPBF
LT1791CN#TRPBF
LT1791CS#TRPBF
1785
8-Lead Plastic SO
8-Lead PDIP
6°C to 76°C
1785I
–46°C to 85°C
–46°C to 85°C
6°C to 76°C
1785I
8-Lead Plastic SO
8-Lead PDIP
1785A
1785A
1785AI
1785AI
1785H
1785H
1785AH
1785AH
1791
8-Lead Plastic SO
8-Lead PDIP
6°C to 76°C
–46°C to 85°C
–46°C to 85°C
–46°C to 125°C
–46°C to 125°C
–46°C to 125°C
–46°C to 125°C
6°C to 76°C
8-Lead Plastic SO
8-Lead PDIP
8-Lead Plastic SO
8-Lead PDIP
8-Lead Plastic SO
14-Lead PDIP
LT1791CS#PBF
1791
14-Lead Plastic SO
6°C to 76°C
Rev. F
2
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
1791I
PACKAGE DESCRIPTION
14-Lead PDIP
TEMPERATURE RANGE
–46°C to 85°C
–46°C to 85°C
6°C to 76°C
LT1791IN#PBF
LT1791IN#TRPBF
LT1791IS#TRPBF
LT1791ACN#TRPBF
LT1791ACS#TRPBF
LT1791AIN#TRPBF
LT1791AIS#TRPBF
LT1791HN#TRPBF
LT1791HS#TRPBF
LT1791AHN#TRPBF
LT1791AHS#TRPBF
LT1791IS#PBF
1791I
14-Lead Plastic SO
14-Lead PDIP
LT1791ACN#PBF
LT1791ACS#PBF
LT1791AIN#PBF
1791A
1791A
14-Lead Plastic SO
14-Lead PDIP
6°C to 76°C
1791AI
1791AI
1791H
–46°C to 85°C
–46°C to 85°C
–46°C to 125°C
–46°C to 125°C
–46°C to 125°C
–46°C to 125°C
LT1791AIS#PBF
14-Lead Plastic SO
14-Lead PDIP
LT1791HN#PBF
LT1791HS#PBF
1791H
14-Lead Plastic SO
14-Lead PDIP
LT1791AHN#PBF
LT1791AHS#PBF
AUTOMOTIꢀE PRODUCTS**
LEAD FREE FINISH
LT1785IS8#WPBF
LT1785AIS8#WPBF
LT1785HS8#WPBF
LT1785AHS8#WPBF
1791AH
1791AH
14-Lead Plastic SO
TAPE AND REEL
PART MARKING*
1785I
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
TEMPERATURE RANGE
–46°C to 85°C
LT1785IS8#WTRPBF
LT1785AIS8#WTRPBF
LT1785HS8#WTRPBF
LT1785AHS8#WTRPBF
1785AI
–46°C to 85°C
1785H
–46°C to 125°C
–46°C to 125°C
1785AH
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 566 unit reels through designated sales channels with #TRMPBF suffix.
**0ersions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These
models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your
local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for
these models.
Rev. F
3
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
DC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, ꢀCC = 5ꢀ.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
0
Differential Driver Output 0oltage (Unloaded)
Differential Driver Output 0oltage (With Load)
I = 6
4.1
5
0
OD1
OD2
O
l
l
l
0
R = 56Ω (RS422), Figure 1
R = 27Ω (RS485), Figure 1
R = 18Ω
2.6
1.5
1.2
2.76
2.45
2.2
0
0
0
l
0
0
Change in Magnitude of Driver Differential Output
0oltage for Complementary Output States
R = 27Ω or R = 56Ω, Figure 1
6.2
0
OD
l
l
Driver Common Mode Output 0oltage
R = 27Ω or R = 56Ω, Figure 1
R = 27Ω or R = 56Ω, Figure 1
2
2
2.5
3
0
0
OC
∆|0
|
Change in Magnitude of Driver Common Mode Output
0oltage for Complementary Output States
6.2
OC
l
l
l
0
0
Input High 0oltage
DI, DE, RE
DI, DE, RE
DI, DE, RE
0
0
IH
Input Low 0oltage
6.8
5
IL
I
Input Current
µA
IN1
IN2
l
l
l
I
Input Current (A, B); (LT1791 or LT1785 with DE = 60)
0
0
= 120
= –70
6.15
–6.68
6.3
mA
mA
mA
IN
IN
–6.15
–±
–±60 ≤ 0 ≤ ±60
±
IN
l
l
0
TH
Differential Input Threshold 0oltage for Receiver
LT1785/LT1791: –70 ≤ 0 ≤ 120
–6.2
–6.2
6.2
6
0
0
CM
LT1785A/LT1791A: –70 ≤ 0 ≤ 120
CM
∆0
Receiver Input Hysteresis
–70 < 0 < 120
26
4
m0
0
TH
CM
l
l
l
0
OH
0
OL
Receiver Output High 0oltage
I = –466µA, 0 = 266m0
3.5
O
ID
Receiver Output Low 0oltage
I = 1.±mA, 0 = –266m0
6.3
6.5
1
0
O
ID
Three-State (High Impedance) Output Current at
RE > 20 or Power Off
–1
85
56
µA
Receiver 60 < 0
< ±0
OUT
l
l
R
IN
Receiver Input Resistance (LT1791)
–70 ≤ 0 ≤ 120
125
125
kΩ
kΩ
CM
– ±60 ≤ 0 ≤ ±60
CM
LT1785
–70 ≤ 0 ≤ 120
96
kΩ
CM
RS485 Unit Load
Driver Short-Circuit Current
6.25
l
l
I
SC
0
OUT
0
OUT
= HIGH, Force 0 = –70
35
35
256
256
mA
mA
O
= LOW, Force 0 = 120
O
l
l
Driver Output Fault Current
0 = ±60
O
±
mA
mA
O
0 = –±60
–±
l
Receiver Short-Circuit Current
60 ≤ 0 ≤ 0
±35
mA
O
CC
l
l
Driver Three-State Output Current
–70 ≤ 0 ≤ 120
–6.2
–±
6.3
±
mA
mA
O
–±60 ≤ 0 ≤ ±60
O
l
l
l
l
I
CC
Supply Current
No Load, RE = 60, DE = 50
No Load, RE = 50, DE = 50
No Load, RE = 60, DE = 60
No Load, RE = 50, DE = 60
5.5
5.5
4.5
6.2
9
9
mA
mA
mA
mA
8
6.3
Rev. F
4
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
SWITCHING CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, ꢀCC = 5ꢀ.
SYMBOL
PARAMETER
CONDITIONS
Figures 3, 5
Figures 3, 5
Figures 3, 5
Figures 3, 5
Figures 4, ±
Figures 4, ±
Figures 4, ±
Figures 4, ±
Figures 3, 7
Figures 3, 7
MIN
TYP
766
766
166
866
566
866
266
866
466
466
266
366
366
466
466
MAX
2666
2666
UNITS
ns
l
l
t
t
t
Driver Input to Output
PLH
Driver Input to Output
ns
PHL
Driver Output to Output
ns
SKEW
l
l
l
l
l
l
l
t , t
r
Driver Rise or Fall Time
266
2666
3666
3666
5666
5666
966
ns
f
t
t
t
t
t
t
t
t
t
t
t
f
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
ns
ZH
ZL
LZ
HZ
ns
ns
ns
ns
PLH
Receiver Input to Output
966
ns
PHL
Differential Receiver Skew
ns
SKD
l
l
l
l
l
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable from Low
Receiver Disable from High
Maximum Data Rate
Figures 2, 8
Figures 2, 8
Figures 2, 8
Figures 2, 8
1666
1666
1666
1666
ns
ZL
ns
ZH
ns
LZ
ns
HZ
256
kbps
µs
MAX
Time to Shut Down
Figures 2, ±, 8
3
12
12
4
SHDN
ZH(SHDN)
ZL(SHDN)
ZH(SHDN)
ZL(SHDN)
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
Figures 2, ±; RE = 50
Figures 2, ±; RE = 50
Figures 2, 8; DE = 60
Figures 2, 8; DE = 60
µs
µs
µs
4
µs
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.
Rev. F
5
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Differential Output ꢀoltage
vs Load Resistance
Driver Differential Output ꢀoltage
vs Temperature
Receiver Propagation Delay
vs Temperature
3.0
2.5
2.0
1.5
1.0
0.5
0
ꢒꢌꢌꢌ
ꢓꢌꢌ
ꢔꢌꢌ
ꢋꢌꢌ
ꢕꢌꢌ
ꢌ
4
3
2
1
0
T
= 25°C
A
ꢛ
ꢃꢜꢎ
ꢛ
ꢃꢎꢜ
R = 27Ω
20
TEMPERATURE (°C)
40
60
80 100
ꢊꢋꢌ
ꢌ
ꢕꢌ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢋꢌ
ꢔꢌ
ꢓꢌ ꢒꢌꢌ
10
100
1k
–40
–20
0
ꢊꢕꢌ
LOAD RESISTANCE (Ω)
178591 G01
178591 G02
ꢒꢖꢓꢗꢘꢒ ꢙꢌꢚ
Driver Propagation Delay
vs Temperature
LT1791 Driver Output Leakage
DE = 0ꢀ
LT1791 Receiver Input Current
vs ꢀIN
ꢖꢌꢌꢌ
ꢗꢌꢌ
ꢘꢌꢌ
ꢙꢌꢌ
ꢚꢌꢌ
ꢛꢌꢌ
ꢋꢌꢌ
ꢜꢌꢌ
ꢝꢌꢌ
ꢖꢌꢌ
ꢌ
ꢒꢞ
ꢞꢒ
ꢀꢁꢂꢃꢄꢅꢆ
ꢀꢁꢁꢂꢃꢄꢅꢆꢇ
ꢎꢌꢆ
ꢎꢁꢇ
ꢍꢎꢌꢆ
ꢏꢎꢁꢇ
ꢆ
ꢅꢏ
ꢇ
ꢆꢐ
ꢀꢇꢈꢉꢊꢀ ꢋꢌꢉ
ꢈꢉꢊꢋꢌꢈ ꢍꢁꢎ
ꢊꢋꢌ
ꢌ
ꢝꢌ
ꢋꢌ
ꢚꢌ
ꢘꢌ ꢖꢌꢌ
ꢊꢝꢌ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢖꢙꢘꢛꢗꢖ ꢎꢌꢋ
LT1785 Input Characteristics Pins
A or B; DE = RE = 0ꢀ
Receiver Propagation Delay
vs Differential Input ꢀoltage
Supply Current vs Temperature
ꢏ
ꢐ
ꢑ
ꢋ
ꢒ
ꢓ
ꢔ
ꢌ
ꢎꢊꢊ
ꢏꢊꢊ
ꢐꢊꢊ
ꢑꢊꢊ
ꢒꢊꢊ
ꢓꢊꢊ
ꢔꢊꢊ
ꢊ
ꢞRꢍꢘꢁR ꢄꢚꢞ
RꢁꢈꢁꢍꢘꢁR ꢙꢚ
ꢘꢇ ꢀ ꢛ ꢜꢎꢀ
ꢙꢚ
ꢘꢇ ꢀ ꢛ ꢔꢓꢀ
ꢙꢚ
RꢁꢈꢁꢍꢘꢁR ꢙꢚꢛꢜ
ꢀꢁꢂꢃꢄꢅꢆ
ꢇꢘ ꢀ ꢛ ꢜꢎꢀ
ꢙꢚ
ꢇꢘ ꢀ ꢛ ꢔꢓꢀ
ꢙꢚ
ꢎꢌꢆ
ꢀꢇꢈꢉꢊꢀ ꢋꢌꢇ
ꢍꢎꢌꢆ
ꢆ ꢏ ꢆ
ꢂ
ꢐ
ꢝꢀꢄꢚꢞꢟꢜ
ꢊ
ꢒ
ꢑ
ꢐ
ꢊꢋꢌ
ꢌ
ꢓꢌ
ꢋꢌ
ꢐꢌ
ꢕꢌ ꢔꢌꢌ
ꢔ
ꢓ
ꢊꢓꢌ
ꢀ
ꢃꢁFFꢄRꢄꢂꢅꢁꢆꢇ ꢈꢀꢉ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢁꢂ
ꢔꢎꢕꢐꢖꢔ ꢗꢊꢖ
ꢔꢏꢕꢑꢖꢔ ꢗꢌꢕ
Rev. F
6
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
PIN FUNCTIONS
RO: Receiver Output. TTL level logic output. If the receiver
is active (RE pin low), RO is high if receiver input A ≥ B
by 266m0. If A ≤ B by 266m0, then RO will be low. RO
assumes a high impedance output state when RE is high
or the part is powered off. RO is protected from output
shorts from ground to ±0.
Y: Driver Output. The Y driver output is in phase with the
driver input DI. In the LT1785 driver output Y is internally
connected to receiver input A. The driver output assumes
a high impedance state when DE is low, power is off or
thermal shutdown is activated. The driver output is pro-
tected from shorts between ±±60 in both active and high
impedance modes. For CAN applications, output Y is the
CANL output node.
RE: Receiver Output Enable. TTL level logic input. A logic
low on RE enables normal operation of the receiver output
RO. A logic high level at RE places the receiver output pin
RO into a high impedance state. If receiver enable RE and
driver enable DE are both in the disable state, the circuit-
goes to a low power shutdown state. Placing either RE or
DE into its active state brings the circuit out of shutdown.
Shutdown state is not entered until a 3µs delay after both
RE and DE are disabled, allowing for logic skews in tog-
gling between transmit and receive modes of operation.
ForCANbusapplications, REshouldbetiedlowtoprevent
the circuit from entering shutdown.
Z: Driver Output. The Z driver output is opposite in phase
to the driver input DI. In the LT1785 driver output Z is
internally connected to receiver input B. The driver output
assumes a high impedance state when DE is low, power
is off or thermal shutdown is activated. The driver output
is protected from shorts between ±±60 in both active and
high impedance modes. For CAN applications, output Z is
the CANH output node.
A:ReceiverInput.TheAreceiverinputforcesahighreceiver
outputwhen0(A)≥[0(B)+266m0].0(A)≤[0(B)–266m0]
forces a receiver output low. Receiver inputs A and B are
protected against voltage faults between ±±60. The high
input impedance allows up to 128 LT1785 or LT1791
transceivers on one RS485 data bus.
DE: Driver Output Enable. TTL level logic input. A logic
high on DE enables normal operation of the driver out-
puts (Y and Z on LT1791, A and B on LT1785). A logic
low level at DE places the driver output pins into a high
impedance state. If receiver enable RE and driver enable
DE are both in the disable state, the circuit goes to a low
power shutdown state. Placing either RE or DE into its
active state brings the circuit out of shutdown. Shutdown
state is not entered until a 3µs delay after both RE and DE
are disabled, allowing for logic skews in toggling between
transmit and receive modes of operation. For CAN bus
operation the DE pin is used for signal input to place the
data bus in dominant or recessive states.
The LT1785A/LT1791A have guaranteed receiver input
thresholds –266m0 < 0 < 6. Receiver outputs are
TH
guaranteed to be in a high state for 60 inputs.
B: Receiver Input. The B receiver input forces a high
receiver output when 0(A) ≥ [0(B) + 266m0]. When
0(A) ≤ [0(B) – 266m0], the B receiver forces a receiver
output low. Receiver inputs A and B are protected against
voltage faults between ±±60. The high input impedance
allows up to 128 LT1785 or LT1791 transceivers on one
RS485 data bus.
DI: Driver Input. TTL level logic input. A logic high at DI
causes driver output A or Y to a high state, and output B
or Z to a low state. Complementary output states occur for
DI low. For CAN bus applications DI should be tied low.
The LT1785A/LT1791A have guaranteed receiver input-
thresholds –266m0 < 0 < 6. Receiver outputs are
TH
guaranteed to be in a high state for 60 inputs.
GND: Ground.
ꢀ :PositiveSupplyInput.ForRS422orRS485operation,
CC
4.750 ≤ 0 ≤ 5.250. Higher 0 input voltages increase
CC
CC
output drive swing. 0 should be decoupled with a 6.1µF
CC
low ESR capacitor directly at Pin 8 (0 ).
CC
Rev. F
7
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
TEST CIRCUITS
ꢃ
ꢋꢉ
ꢋꢌ
ꢆꢀꢋꢆ ꢇꢄꢂꢍꢆ
ꢉꢊ
R
RꢀꢁꢀꢂꢃꢀR
ꢄꢅꢆꢇꢅꢆ
ꢃ
ꢁꢁ
ꢀ
ꢁꢂ
ꢉꢊ
ꢀ
ꢁꢅ
ꢁ
Rꢈ
R
ꢄ
ꢉꢎꢏꢐꢑꢒꢉ Fꢓꢌ
ꢆꢇꢈꢉꢊꢋꢆ Fꢌꢆ
Figure 1. Driver DC Test Load
Figure 2. Receiver Timing Test Load
ꢀꢁ
ꢂꢃ
ꢄ
S1
ꢄ
ꢅ
ꢇ
ꢇ
ꢈꢉ
ꢂꢆ
V
CC
Rꢋ
R
ꢂꢆFF
500Ω
OUTPUT
UNDER TEST
ꢅ
S2
ꢈꢊ
RE
ꢉꢀꢌF
C
L
1785/91 F04
ꢉꢍꢎꢀꢏꢐꢉ Fꢑꢒ
Figure 3. Driver/Receiver Timing Test Circuit
Figure 4. Driver Timing Test Load
Rev. F
8
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
FUNCTION TABLES
LT1785 Transmitting
INPUTS
LT1791
OUTPUTS
INPUTS
DI
OUTPUTS
RE
6
DE
1
DI
6
A
6
B
1
RO
6
RE
6
6
6
6
6
6
6
6
6
1
1
1
DE
6
6
6
1
1
1
1
1
1
6
1
1
A-B
≤ –266m0
≥ 266m0*
Open
Y
Hi-Z
Hi-Z
Hi-Z
6
Z
Hi-Z
Hi-Z
Hi-Z
1
RO
6
X
X
X
6
6
6
1
1
1
X
6
1
6
1
1
1
6
1
1
1
6
X
6
Hi-Z
6
Hi-Z
1
Hi-Z
Hi-Z
Hi-Z
1**
6
1
1
≤ –266m0
≥ 266m0*
Open
1
1
1
1
6
6
1
1
6
1
1**
6
LT1785 Receiving
INPUTS
≤ –266m0
≥ 266m0*
Open
1
6
OUTPUT
1
6
1
RE
6
DE
6
DI
X
A-B
RO
6
1
6
1**
Hi-Z
Hi-Z
Hi-Z
≤ –266m0
≥ 266m0*
Open
X
Hi-Z
6
Hi-Z
1
6
6
X
1
X
6
6
X
1**
Hi-Z
X
1
6
1
6
X
X
* ≥ 6m0 for LT1791A
** 1 for LT1791A; 1 or 6 for LT1791
* ≥ 6m0 for LT1785A
** 1 for LT1785A; 1 or 6 for LT1785
Rev. F
9
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
SWITCHING TIME WAVEFORMS
5V
f = 125kHz, t ≤ 10ns, t ≤ 10ns
DI
1.5V
1.5V
r
f
0V
B
1/2 V
O
t
t
PHL
PLH
V
O
A
t
t
SKEW
1/2 V
SKEW
O
V
O
90%
10%
90%
V
= V(A) – V(B)
0V
DIFF
10%
–V
O
t
t
f
1785/91 F05
r
Figure 5. Driver Propagation Delays
5V
0V
5V
f = 125kHz, t ≤ 10ns, t ≤ 10ns
1.5V
1.5V
DE
A, B
A, B
r
f
t
t
, t
LZ
ZL(SHDN) ZL
2.3V
OUTPUT NORMALLY LOW
0.5V
0.5V
V
OL
OH
0V
V
OUTPUT NORMALLY HIGH
, t
2.3V
t
t
178591 F06
HZ
ZH(SHDN) ZH
Figure ±. Driver Enable and Disable Times
V
OH
1.5V
1.5V
RO
OUTPUT
V
OL
OD2
OD2
t
f = 125kHz, t ≤ 10ns, t ≤ 10ns
t
PHL
r
f
PLH
V
A – B
–V
0V
0V
INPUT
178591 F07
Figure 7. Receiver Propagation Delays
5V
0V
5V
1.5V
1.5V
RE
RO
RO
f = 125kHz, t ≤ 10ns, t ≤ 10ns
r
f
t
, t
t
LZ
ZL(SHDN) ZL
1.5V
OUTPUT NORMALLY LOW
0.5V
0.5V
OUTPUT NORMALLY HIGH
, t
1.5V
t
0V
t
HZ
178591 F08
ZH(SHDN) ZH
Figure 8. Receiver Enable and Disable Times
Rev. F
10
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
APPLICATIONS INFORMATION
Overvoltage Protection
LT1785 pins A and B and the LT1791 driver output pins Y
andZareprotectedtoIEC-1666-4-2level2.Thesepinswill
survivemultipleESDstrikesof±15k0airdischargeor±4k0
contactdischarge.Duetotheirveryhighinputimpedance,
the LT1791 receiver pins are protected to IEC-1666-4-2
level 2, or ±15k0 air and ±4k0 contact discharges. This
level of ESD protection will guarantee immunity from field
failures in all but the most severe ESD environments. The
LT1791 receiver input ESD tolerance may be increased to
IEC level 4 compliance by adding 2.2k resistors in series
with these pins.
TheLT1785/LT1791RS485/RS422transceiversansweran
applications need for overvoltage fault tolerance on data
networks. Industrialinstallationsmayencountercommon
mode voltages between nodes far greater than the –70 to
120 range specified for compliance to RS485 standards.
CMOS RS485 transceivers can be damaged by voltages
above their absolute maximum ratings of typically –80
to 12.50. Replacement of standard RS485 transceiver
componentswiththeLT1785orLT1791deviceseliminates
field failures due to overvoltage faults or the use of costly
external protection devices. The limited overvoltage toler-
anceofCMOSRS485transceiversmakesimplementation
of effective external protection networks difficult without
interfering with proper data network performance within
the –70 to 120 region of RS485 operation.
Low Power Shutdown
TheLT1785/LT1791haveREandDElogicinputstocontrol
the receive and transmit modes of the transceivers. The
RE input allows normal data reception when in the low
state. The receiver output goes to a high impedance state
when RE is high, allowing multiplexing the RO data line.
TheDElogicinputperformsasimilarfunctiononthedriver
outputs. A high state on DE activates the differential driver
outputs, a low state places both driver outputs in to high
impedance. TyingtheREandDElogicinputstogethermay
be done to allow one logic signal to toggle the transceiver
from receive to transmit modes. The DE input is used as
the data input in CAN bus applications.
The high overvoltage rating of the LT1785/LT1791 facili-
tates easy extension to almost any level. Simple discrete
component networks that limit the receiver input and
driver output voltages to less than ±±60 can be added
to the device to extend protection to any desired level.
Figure 11 shows a protection network against faults to
the1260AC line voltage.
The LT1785/LT1791 protection is achieved by using a high
voltagebipolarintegratedcircuitprocessforthetransceiv-
ers. The naturally high breakdown voltages of the bipolar
process provides protection in powered-off and high
impedance conditions. The driver outputs use a foldback
current limit design to protect against overvoltage faults
while still allowing high current output drive.
Disabling both the driver and receiver places the device
into a low supply current shutdown mode. An internal
time delay of 3µs minimum prevents entering shutdown
due to small logic skews when a toggle between receive
and transmit is desired. The recovery time from shutdown
mode is typically 12µs. The user must be careful to allow
for this wake-up delay from shutdown mode. To allow full
256kbaud data rate transmission in CAN applications, the
RE pin should be tied low to prevent entering shutdown
mode.
ESD Protection
The LT1785/LT1791 I/O pins have on-chip ESD protection
circuitry to eliminate field failures caused by discharges to
exposedportsandcablesinapplicationenvironments.The
Rev. F
11
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
APPLICATIONS INFORMATION
Slew Limiting for EMI Emissions Control
Data Network Cable Selection and Termination
The LT1785/LT1791 feature controlled driver output slew
ratestocontrolhighfrequencyEMIemissionsfromequip-
ment and data cables. The slew limiting limits data rate
operation to 256kbaud. Slew limiting also mitigates the
adverse affects of imperfect transmission line termina-
tion caused by stubs or mismatched cable. In some low
speed, short distance networks, cable termination may
be eliminated completely with no adverse effect on data
transmission.
Long distance data networks operating at high data trans-
mission rates should use high quality, low attenuation
cablewithwell-matchedcableterminations.Shortdistance
networks at low data rates may use much less expensive
P0C cable. These cables have characteristic impedances
as low as 72Ω. The LT1785/LT1791 output drivers are
guaranteed to drive cables as low as 72Ω.
12
11
A
B
9
Y
Z
5
2
120Ω
RX
DI
RO
TX
10
3
4
4
3
RE
DE
LT1791
LT1791
DE
RE
B
A
10
9
11
12
Z
2
5
120Ω
TX
RO
DI
RX
Y
178591 F09
Figure 9. Full-Duplex RS422
Rev. F
12
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
PACKAGE DESCRIPTION
N Package
8-Lead PDIP (Narrow .300 Inch)
ꢊReꢣeꢤeꢥꢦe ꢟꢌꢝ ꢛꢧꢨ ꢩ ꢅꢉꢪꢅꢁꢪꢇꢉꢇꢅ Rev ꢄꢋ
.ꢏꢅꢅꢖ
ꢊꢇꢅ.ꢇꢈꢅꢋ
ꢓꢗꢘ
ꢁ
ꢆ
ꢈ
ꢉ
ꢏ
.ꢒꢉꢉ ±.ꢅꢇꢉꢖ
ꢊꢈ.ꢏꢆꢆ ±ꢅ.ꢑꢁꢇꢋ
ꢇ
ꢒ
ꢑ
.ꢇꢑꢅ ±.ꢅꢅꢉ
.ꢑꢅꢅ ꢐ .ꢑꢒꢉ
.ꢅꢏꢉ ꢐ .ꢅꢈꢉ
ꢊꢑ.ꢑꢅꢒ ±ꢅ.ꢇꢒꢆꢋ
ꢊꢇ.ꢇꢏꢑ ꢐ ꢇ.ꢈꢉꢇꢋ
ꢊꢆ.ꢈꢒꢅ ꢐ ꢁ.ꢒꢉꢉꢋ
.ꢅꢈꢉ
ꢊꢇ.ꢈꢉꢇꢋ
ꢌꢍꢎ
.ꢅꢅꢁ ꢐ .ꢅꢇꢉ
ꢊꢅ.ꢒꢅꢑ ꢐ ꢅ.ꢑꢁꢇꢋ
.ꢇꢒꢅ
.ꢅꢒꢅ
ꢊꢅ.ꢉꢅꢁꢋ
ꢓꢄꢀ
ꢊꢑ.ꢅꢏꢁꢋ
ꢓꢄꢀ
ꢔ.ꢅꢑꢉ
.ꢑꢒꢉ
ꢐ.ꢅꢇꢉ
.ꢅꢇꢁ ±.ꢅꢅꢑ
ꢊꢅ.ꢏꢉꢆ ±ꢅ.ꢅꢆꢈꢋ
.ꢇꢅꢅ
ꢊꢒ.ꢉꢏꢋ
ꢢꢜꢝ
ꢔꢅ.ꢁꢁꢕ
ꢁ.ꢒꢉꢉ
ꢀꢁ Rꢂꢃ ꢄ ꢅꢆꢇꢇ
(
)
ꢐꢅ.ꢑꢁꢇ
ꢀꢙꢌꢂꢚ
ꢄꢀꢝꢞꢂꢜ
ꢇ. ꢛꢄꢓꢂꢀꢜꢄꢙꢀꢜ ꢗRꢂ
ꢓꢄꢟꢟꢄꢓꢂꢌꢂRꢜ
ꢖꢌꢞꢂꢜꢂ ꢛꢄꢓꢂꢀꢜꢄꢙꢀꢜ ꢛꢙ ꢀꢙꢌ ꢄꢀꢝꢟꢠꢛꢂ ꢓꢙꢟꢛ Fꢟꢗꢜꢞ ꢙR ꢎRꢙꢌRꢠꢜꢄꢙꢀꢜ.
ꢓꢙꢟꢛ Fꢟꢗꢜꢞ ꢙR ꢎRꢙꢌRꢠꢜꢄꢙꢀꢜ ꢜꢞꢗꢟꢟ ꢀꢙꢌ ꢂꢘꢝꢂꢂꢛ .ꢅꢇꢅ ꢄꢀꢝꢞ ꢊꢅ.ꢒꢉꢏꢡꢡꢋ
Rev. F
13
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
ꢅReꢤeꢥeꢦꢧe ꢛꢋꢖ ꢚꢠꢓ ꢨ ꢀꢄꢩꢀꢊꢩꢁꢂꢁꢀ Rev ꢓꢉ
.ꢁꢊꢔ ꢃ .ꢁꢔꢈ
ꢅꢆ.ꢊꢀꢁ ꢃ ꢄ.ꢀꢀꢆꢉ
.ꢀꢆꢄ ±.ꢀꢀꢄ
ꢗꢐꢋꢑ ꢎ
.ꢀꢄꢀ ꢕꢏꢖ
ꢈ
ꢄ
ꢊ
ꢂ
.ꢇꢆꢄ
ꢘꢙꢗ
.ꢁꢂꢀ ±.ꢀꢀꢄ
.ꢁꢄꢀ ꢃ .ꢁꢄꢈ
ꢅꢎ.ꢊꢁꢀ ꢃ ꢎ.ꢔꢊꢊꢉ
ꢗꢐꢋꢑ ꢎ
.ꢇꢇꢊ ꢃ .ꢇꢆꢆ
ꢅꢄ.ꢈꢔꢁ ꢃ ꢂ.ꢁꢔꢈꢉ
.ꢀꢎꢀ ±.ꢀꢀꢄ
ꢋꢌꢍ
ꢁ
ꢎ
ꢆ
ꢇ
Rꢑꢖꢐꢘꢘꢑꢗꢚꢑꢚ ꢏꢐꢛꢚꢑR ꢍꢜꢚ ꢛꢜꢌꢐꢝꢋ
.ꢀꢁꢀ ꢃ .ꢀꢇꢀ
ꢅꢀ.ꢇꢄꢆ ꢃ ꢀ.ꢄꢀꢊꢉ
× ꢆꢄ°
.ꢀꢄꢎ ꢃ .ꢀꢂꢔ
ꢅꢁ.ꢎꢆꢂ ꢃ ꢁ.ꢈꢄꢇꢉ
.ꢀꢀꢆ ꢃ .ꢀꢁꢀ
ꢅꢀ.ꢁꢀꢁ ꢃ ꢀ.ꢇꢄꢆꢉ
.ꢀꢀꢊ ꢃ .ꢀꢁꢀ
ꢅꢀ.ꢇꢀꢎ ꢃ ꢀ.ꢇꢄꢆꢉ
ꢀ°ꢃ ꢊ° ꢋꢌꢍ
.ꢀꢁꢂ ꢃ .ꢀꢄꢀ
ꢅꢀ.ꢆꢀꢂ ꢃ ꢁ.ꢇꢈꢀꢉ
.ꢀꢄꢀ
ꢅꢁ.ꢇꢈꢀꢉ
ꢕꢏꢖ
.ꢀꢁꢆ ꢃ .ꢀꢁꢔ
ꢅꢀ.ꢎꢄꢄ ꢃ ꢀ.ꢆꢊꢎꢉ
ꢋꢌꢍ
ꢗꢐꢋꢑꢟ
ꢙꢗꢖꢞꢑꢏ
ꢁ. ꢚꢙꢘꢑꢗꢏꢙꢐꢗꢏ ꢙꢗ
ꢅꢘꢙꢛꢛꢙꢘꢑꢋꢑRꢏꢉ
ꢇ. ꢚRꢜꢠꢙꢗꢓ ꢗꢐꢋ ꢋꢐ ꢏꢖꢜꢛꢑ
ꢎ. ꢋꢞꢑꢏꢑ ꢚꢙꢘꢑꢗꢏꢙꢐꢗꢏ ꢚꢐ ꢗꢐꢋ ꢙꢗꢖꢛꢝꢚꢑ ꢘꢐꢛꢚ Fꢛꢜꢏꢞ ꢐR ꢍRꢐꢋRꢝꢏꢙꢐꢗꢏ.
ꢘꢐꢛꢚ Fꢛꢜꢏꢞ ꢐR ꢍRꢐꢋRꢝꢏꢙꢐꢗꢏ ꢏꢞꢜꢛꢛ ꢗꢐꢋ ꢑꢡꢖꢑꢑꢚ .ꢀꢀꢂꢢ ꢅꢀ.ꢁꢄꢣꢣꢉ
ꢆ. ꢍꢙꢗ ꢁ ꢖꢜꢗ ꢕꢑ ꢕꢑꢒꢑꢛ ꢑꢚꢓꢑ ꢐR ꢜ ꢚꢙꢘꢍꢛꢑ
ꢏꢐꢊ Rꢑꢒ ꢓ ꢀꢇꢁꢇ
Rev. F
14
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
PACKAGE DESCRIPTION
N Package
14-Lead PDIP (Narrow .300 Inch)
ꢉReꢣeꢤeꢥꢦe ꢟꢑꢝ ꢛꢧꢨ ꢩ ꢆꢊꢪꢆꢋꢪꢁꢊꢁꢆ Rev ꢅꢌ
.ꢇꢇꢆꢔ
ꢉꢁꢕ.ꢊꢊꢋꢌ
ꢍꢖꢗ
ꢁꢂ
ꢁꢎ
ꢁꢈ
ꢁꢁ
ꢁꢆ
ꢕ
ꢋ
ꢇ
.ꢈꢊꢊ .ꢆꢁꢊꢔ
ꢉꢐ.ꢂꢇꢇ ꢆ.ꢎꢋꢁꢌ
ꢁ
ꢈ
ꢎ
ꢊ
ꢐ
ꢂ
.ꢎꢆꢆ ꢏ .ꢎꢈꢊ
ꢉꢇ.ꢐꢈꢆ ꢏ ꢋ.ꢈꢊꢊꢌ
.ꢆꢂꢊ ꢏ .ꢆꢐꢊ
ꢉꢁ.ꢁꢂꢎ ꢏ ꢁ.ꢐꢊꢁꢌ
.ꢁꢎꢆ .ꢆꢆꢊ
ꢉꢎ.ꢎꢆꢈ ꢆ.ꢁꢈꢇꢌ
.ꢆꢈꢆ
ꢉꢆ.ꢊꢆꢋꢌ
ꢍꢅꢀ
.ꢆꢐꢊ
ꢉꢁ.ꢐꢊꢁꢌ
ꢑꢒꢓ
.ꢆꢆꢋ ꢏ .ꢆꢁꢊ
ꢉꢆ.ꢈꢆꢎ ꢏ ꢆ.ꢎꢋꢁꢌ
ꢘ.ꢆꢎꢊ
.ꢎꢈꢊ
.ꢆꢆꢊ
ꢉꢆ.ꢁꢈꢇꢌ
ꢍꢅꢀ
ꢏ.ꢆꢁꢊ
.ꢁꢈꢆ
ꢉꢎ.ꢆꢂꢋꢌ
ꢍꢅꢀ
.ꢆꢁꢋ .ꢆꢆꢎ
.ꢁꢆꢆ
ꢉꢈ.ꢊꢂꢌ
ꢢꢜꢝ
ꢘꢆ.ꢋꢋꢕ
ꢋ.ꢈꢊꢊ
ꢉꢆ.ꢂꢊꢇ ꢆ.ꢆꢇꢐꢌ
(
)
ꢏꢆ.ꢎꢋꢁ
ꢀꢁꢂ Rꢃꢄ ꢅ ꢆꢇꢁꢁ
ꢀꢙꢑꢃꢚ
ꢅꢀꢝꢞꢃꢜ
ꢍꢅꢟꢟꢅꢍꢃꢑꢃRꢜ
ꢁ. ꢛꢅꢍꢃꢀꢜꢅꢙꢀꢜ ꢖRꢃ
ꢔꢑꢞꢃꢜꢃ ꢛꢅꢍꢃꢀꢜꢅꢙꢀꢜ ꢛꢙ ꢀꢙꢑ ꢅꢀꢝꢟꢠꢛꢃ ꢍꢙꢟꢛ Fꢟꢖꢜꢞ ꢙR ꢓRꢙꢑRꢠꢜꢅꢙꢀꢜ.
ꢍꢙꢟꢛ Fꢟꢖꢜꢞ ꢙR ꢓRꢙꢑRꢠꢜꢅꢙꢀꢜ ꢜꢞꢖꢟꢟ ꢀꢙꢑ ꢃꢗꢝꢃꢃꢛ .ꢆꢁꢆ ꢅꢀꢝꢞ ꢉꢆ.ꢈꢊꢂꢡꢡꢌ
Rev. F
15
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
PACKAGE DESCRIPTION
S Package
14-Lead Plastic Small Outline (Narrow .150 Inch)
ꢏReꢐeꢑeꢒꢓe ꢊꢔꢅ ꢋꢕꢌ ꢖ ꢗꢘꢙꢗꢚꢙꢄꢛꢄꢗ Rev ꢌꢜ
.337 – .344
.045 .005
(8.560 – 8.738)
.050 BSC
NOTE 3
13
12
11
10
8
14
N
9
N
1
.245
MIN
.160 .005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
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 REV G 0212
NOTE:
INCHES
(MILLIMETERS)
2. DRAWING NOT TO SCALE
1. DIMENSIONS IN
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
ꢀ. ꢁꢂꢃ ꢄ ꢅꢆꢃ ꢇꢈ ꢇꢈꢉꢈꢊ ꢈꢋꢌꢈ ꢍR ꢆ ꢋꢂꢎꢁꢊꢈ
Rev. F
16
For more information www.analog.com
LT1785/LT1785A/
LT1791/LT1791A
REVISION HISTORY (Revision history begins at Rev D)
REꢀ
DATE
DESCRIPTION
PAGE NUMBER
D
63/15 Added notes to Function Tables
9
E
12/19 Added Auto Grade
1, 3
3
Removed lead based finish part options
63/26 Added Auto Grade for H temp range
F
3
Rev. F
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
17
LT1785/LT1785A/
LT1791/LT1791A
TYPICAL APPLICATION
R
R
T
120Ω
1
1
T
RO
RO
RX
RX
120Ω
7
6
B
A
7
6
B
A
2
3
2
3
RE
RE
LT1785
LT1785
DE
DE
6
A
7
B
6
A
7
B
4
4
DI
DI
TX
TX
178591 F10
LT1785
LT1785
4
4
1
1
3
2
3
2
DI
DI
DE
DE
RE RO
RE RO
Figure 10. Half-Duplex RS485 Network Operation
RAYCHEM
POLYSWITCH
8
TR600-150
V
CC
1
× 2
RO
47Ω
RX
7
B
A
2
3
R ,120Ω
T
RE
LT1785
DE
6
5
178591 F11
0.1µF
300V
47Ω
CARBON
4
DI
TX
COMPOSITE
5W
1.5KE36CA
Figure 11. RS485 Network with 120ꢀ AC Line Fault Protection
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC2854/LTC2855 3.30 26Mbps RS485/RS422 Transceivers with Integrated
Switchable Termination
Up to ±25k0 HBM ESD, 125°C Operation
LTC285±/LTC2857/ 50 26Mbps and Slew Rate Limited 15k0 RS485/RS422
±15k0 ESD, 125°C Operation
LTC2858
Transceivers
LTC2856/LTC2851/ 3.30 26Mbps RS485/RS422 Transceivers
LTC2852
±15k0 ESD, 125°C Operation
LTC2859/LTC28±1 26Mbps RS485 Transceivers with Integrated Switchable
Termination
Integrated, Switchable,126Ω Termination Resistor, ±15k0 ESD
LTC28±2/LTC28±3/ ±±60 Fault Protected 30 to 5.50 RS485/RS422 Transceivers
LTC28±4/LTC28±5
26Mbps or 256kbps, ±15k0 HBM ESD, ±250 Common Mode
Range
LTM2881
Complete 3.30 Isolated RS485/RS422 µModule® Transceiver
+ Power
25660
Isolation with Integrated Isolated DC/DC Converter and
RMS
Switchable Termination
Rev. F
03/20
www.analog.com
18
ANALOG DEVICES, INC. 1998–2020
相关型号：
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LT1785AHN8#TR
IC LINE TRANSCEIVER, PDIP8, 0.300 INCH, PLASTIC, DIP-8, Line Driver or Receiver
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