LTC1685
52Mbps, Precision Delay,
RS485 Fail-Safe Transceiver
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DESCRIPTIO
FEATURES
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Precision Propagation Delay Over Temperature:
Receiver/Driver: 18.5ns ±3.5ns
High Data Rate: 52Mbps
Low tPLH/tPHL Skew:
Receiver/Driver: 500ps Typ
–7V to 12V RS485 Input Common Mode Range
Guaranteed Fail-Safe Receiver Operation Over the
Entire Common Mode Range
High Receiver Input Resistance: ≥ 22k, Even When
Unpowered
Short-Circuit Protected
Thermal Shutdown Protected
Driver Maintains High Impedance in Three-State or
with Power Off
Single 5V Supply
Pin Compatible with LTC485
45dB CMRR at 26MHz
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APPLICATIO S
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High Speed RS485/RS422 Transceivers
Level Translator
Backplane Transceiver
STS-1/OC-1 Data Transceiver
Fast-20, Fast-40 SCSI Transceivers
A unique architecture provides very stable propagation
delays and low skew over a wide common mode and
ambient temperature range.
The driver and receiver feature three-state outputs, with
disabled driver outputs maintaining high impedance over
the entire common mode range. A short circuit feature
detects shorted outputs and substantially reduces driver
output current. A similar feature also protects the receiver
output from short circuits. Thermal shutdown circuitry
protects from excessive power dissipation.
The receiver has a fail-safe feature that guarantees a high
output state when the inputs are shorted or are left floating.
The LTC1685 RS485 transceiver guarantees receiver failsafe operation over the entire common mode range (– 7V
to 12V). Input resistance will remain ≥ 22k when the device
is unpowered or disabled.
The LTC1685 operates from a single 5V supply and draws
only 7mA of supply current.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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The LTC®1685 is a high speed, precision delay RS485
transceiver that can operate at data rates as high as 52Mbps.
The device also meets the requirements of RS422.
TYPICAL APPLICATION
RO1
R
10Mbps Data Pulse
400ft Category 5 UTP
VCC1
RE1
DI1
2V/DIV
Rt
DE1
D
DRIVER INPUT
CABLE DELAY
GND1
1V/DIV
RECEIVER
INPUT
5V/DIV
RECEIVER
OUTPUT
Rt
RO2
R
VCC2
RE2
DE2
DI2
D
GND2
1685 TA01
100ns/DIV
1685 TA02
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