lt1785ais8-trpbf Linear Technology Corporation, lt1785ais8-trpbf Datasheet

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lt1785ais8-trpbf

Manufacturer Part Number
lt1785ais8-trpbf
Description
60v Fault Protected Rs485/rs422 Transceivers
Manufacturer
Linear Technology Corporation
Datasheet
FEATURES
TYPICAL APPLICATIO
APPLICATIO S
Protected from Overvoltage Line Faults to 60V
Pin Compatible with LTC485 and LTC491
High Input Impedance Supports Up to 128 Nodes
No Damage or Latchup to ESD
Controlled Slew Rates for EMI Emissions Control
Guaranteed High Receiver Output State for Floating,
Shorted or Inactive Inputs
Outputs Assume a High Impedance When Off or
Powered Down
Drives Low Cost, Low Impedance Cables
Short-Circuit Protection on All Outputs
Thermal Shutdown Protection
Industrial Control Data Networks
CAN Bus Applications
HVAC Controls
IEC-1000-4-2 Level 4: 15kV Air Discharge
IEC-1000-4-2 Level 2: 4kV Contact Discharge
RO1
RO2
RE1
DE1
RE2
DE2
DI1
DI2
U
TX
TX
LT1785
LT1785
RX
RX
U
V
GND1
V
GND2
CC2
CC1
R
R
TERM
TERM
1785/91 TA01
DESCRIPTIO
The LT
ferential bus transceivers for RS485 and RS422 applica-
tions 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 60V
with respect to ground with no damage to the device.
Faults may occur while the transceiver is active, shut down
or powered off.
Data rates to 250kbaud on networks of up to 128 nodes are
supported. Controlled slew rates on the driver outputs
control EMI emissions and improve data transmission
integrity on improperly terminated lines. Drivers are speci-
fied to operate with inexpensive cables as low as 72
characteristic impedance.
The LT1785A/LT1791A devices have “fail-safe” receiver
inputs to guarantee a receiver output high for shorted,
open or inactive data lines. On-chip ESD protection elimi-
nates need for external protection devices.
The LT1785/LT1785A are available in 8-lead DIP and SO
packages and the LT1791/LT1791A in 14-lead DIP and SO
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
®
1785/LT1791 are half-duplex and full-duplex dif-
Y-Z
RO
RS485/RS422 Transceivers
DI
Normal Operation Waveforms at 250kBaud
60V Fault Protected
U
LT1785/LT1785A
LT1791/LT1791A
1785/91 TA02
1

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lt1785ais8-trpbf Summary of contents

Page 1

... On-chip ESD protection elimi- nates need for external protection devices. The LT1785/LT1785A are available in 8-lead DIP and SO packages and the LT1791/LT1791A in 14-lead DIP and SO packages. , LTC and LT are registered trademarks of Linear Technology Corporation. CC1 R TERM RO Y-Z ...

Page 2

... W U ORDER PART NUMBER LT1785CN8 LT1785CS8 NC 1 LT1785IN8 RO 2 LT1785IS8 RE 3 LT1785ACN8 DE 4 LT1785ACS8 DI 5 LT1785AIN8 GND 6 LT1785AIS8 GND 7 N PACKAGE S8 PART MARKING 14-LEAD PDIP T = 150 C, JMAX 1785 T = 150 C, JMAX 1785I 1785A 1785AI ORDER PART NUMBER LT1791CN TOP VIEW LT1791CS ...

Page 3

DC ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are SYMBOL PARAMETER V Differential Driver Output Voltage (Unloaded) OD1 V Differential Driver Output Voltage (With Load) OD2 ...

Page 4

LT1785/LT1785A LT1791/LT1791A U SWITCHI G CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are SYMBOL PARAMETER t Driver Input to Output PLH t Driver Input to Output PHL ...

Page 5

W U TYPICAL PERFORMANCE CHARACTERISTICS Driver Propagation Delay vs Temperature 1000 900 800 LH 700 600 HL 500 400 300 200 100 0 – 100 –20 80 TEMPERATURE ( C) 1785/91 G04 LT1785 Input Characteristics Pins ...

Page 6

LT1785/LT1785A LT1791/LT1791A PIN FUNCTIONS 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 into its active state ...

Page 7

TEST CIRCUITS DIFF Figure 3. Driver/Receiver Timing Test Circuit CTIO TABLES LT1785 Transmitting INPUTS ...

Page 8

LT1785/LT1785A LT1791/LT1791A U W SWITCHI WAVEFOR OD2 A – B –V OD2 ...

Page 9

U U APPLICATIO S I FOR ATIO 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 60V can ...

Page 10

LT1785/LT1785A LT1791/LT1791A U U APPLICATIO S I FOR ATIO PACKAGE DESCRIPTION 0.300 – 0.325 (7.620 – 8.255) 0.065 (1.651) 0.009 – 0.015 TYP (0.229 – 0.381) +0.035 0.325 –0.015 +0.889 ...

Page 11

... 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- tation that the interconnection of circuits as described herein will not infringe on existing patent rights. ...

Page 12

... Up to 256 Transceivers on the Bus Channel-to-Channel Skew 400ps (Typ) 2500V Isolation in Surface Mount Package RMS Propagation Delay Skew 500ps (Typ) Propagation Delay Skew 500ps (Typ) 178591fa LT/TP 0501 2K REV A • PRINTED IN THE USA LINEAR TECHNOLOGY CORPORATION 1998 ...

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