Datasheet
1
LTC1686/LTC1687
52Mbps Precision Delay
RS485 Fail-Safe Transceivers
DESCRIPTION
U
■
Precision Propagation Delay Over Temperature:
Receiver/Driver: 18.5ns
±
3.5ns
■
High Data Rate:
52Mbps
■
Low t
PLH
/t
PHL
Skew:
Receiver/Driver: 500ps Typ
■
–7V to 12V RS485 Input Common Mode Range
■
Guaranteed Fail-Safe Operation Over the Entire
Common Mode Range
■
High Input Resistance: ≥22k, Even When Unpowered
■
Short-Circuit Protected
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Thermal Shutdown Protected
■
Driver Maintains High Impedance in Three-State or
with Power Off
■
Single 5V Supply
■
Pin Compatible with LTC490/LTC491
■
45dB CMRR at 26MHz
FEATURES
The LTC
®
1686/LTC1687 are high speed, precision delay,
full-duplex RS485 transceivers that can operate at data
rates as high as 52Mbps. The devices also meet the
requirements of RS422.
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 LTC1686/LTC1687 RS485 transceivers guarantee
receiver fail-safe operation over the
entire
common mode
range (–7V to 12V). Receiver input resistance remains
≥22k when the device is unpowered or disabled.
The LTC1686/LTC1687 operate from a single 5V supply
and draw only 7mA of supply current.
APPLICATIONS
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High Speed RS485/RS422 Full Duplex Transceivers
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Level Translator
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Backplane Transceiver
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STS-1/OC-1 Data Transceiver
■
Signal Repeaters
, LTC and LT are registered trademarks of Linear Technology Corporation.
10Mbps Data Pulse
400 Feet Category 5 UTP
1686/87 TA02
DRIVER INPUT
RECEIVER
INPUT
RECEIVER
OUTPUT
100ns/DIV
1V/DIV
2V/DIV
5V/DIV
CABLE DELAY
LTC1686/87 • TA01
100Ω 100Ω
100Ω 100Ω
LTC1686 LTC1686
R
D
R
D
3
2
7
8
6
5
400 FT OF CATEGORY 5 UTP
RECEIVER
DRIVER
RECEIVER
DRIVER
TYPICAL APPLICATION
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