
1
LTC1686/LTC1687
52Mbps Precision Delay
RS485 Fail-Safe Transceivers
DESCRIPTION
U
s
Precision Propagation Delay Over Temperature:
Receiver/Driver: 18.5ns
±3.5ns
s
High Data Rate:
52Mbps
s
Low tPLH/tPHL Skew:
Receiver/Driver: 500ps Typ
s
–7V to 12V RS485 Input Common Mode Range
s
Guaranteed Fail-Safe Operation Over the Entire
Common Mode Range
s
High Input Resistance:
≥22k, Even When Unpowered
s
Short-Circuit Protected
s
Thermal Shutdown Protected
s
Driver Maintains High Impedance in Three-State or
with Power Off
s
Single 5V Supply
s
Pin Compatible with LTC490/LTC491
s
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
U
s
High Speed RS485/RS422 Full Duplex Transceivers
s
Level Translator
s
Backplane Transceiver
s
STS-1/OC-1 Data Transceiver
s
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
100
100
100
100
LTC1686
R
D
R
D
3
2
7
8
6
5
400 FT OF CATEGORY 5 UTP
RECEIVER
DRIVER
RECEIVER
DRIVER
TYPICAL APPLICATION
U