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Bus Transceiver
General Description
The DS3662 is a quad high speed Schottky bus transceiver
intended for use with terminated 120鈩?impedance lines. It is
specifically designed to reduce noise in unbalanced trans-
mission systems. The open collector drivers generate pre-
cise trapezoidal waveforms with rise and fall times of 15 ns
(typical), which are relatively independent of capacitive load-
ing conditions on the outputs. This reduces noise coupling to
the adjacent lines without any appreciable impact on the
maximum data rate obtainable with high speed bus trans-
ceivers. In addition, the receivers use a low pass filter in con-
junction with a high speed comparator, to further enhance
the noise immunity. Tightly controlled threshold levels on the
receiver provide equal rejection to both negative and positive
going noise pulses on the bus.
The external termination is intended to be a 180鈩?resistor
from the bus to 5V logic supply, together with a 390鈩?resistor
from the bus to ground. The bus can be terminated at one or
both ends. A two input NOR gate is provided to disable all
drivers in a package simultaneously.
Features
n
Pin to pin functional replacement for DS8641
n
Guaranteed AC specifications on noise immunity and
propagation delay over the specified temperature and
supply voltage range
n
Temperature insensitive receiver thresholds track bus
logic level
n
Trapezoidal bus waveforms reduce noise coupling to
adjacent lines
n
Precision receiver thresholds provide maximum noise
immunity and symmetrical response to positive and
negative going pulses
n
Open collector driver output allows wire-OR connection
n
High speed Schottky technology
n
15 碌A(chǔ) typical bus termination current with normal V
CC
or
with V
CC
= 0V
n
Glitch free power up/down protection on the driver
output
n
TTL compatible driver and disable inputs, and receiver
outputs
Block and Connection Diagram
Dual-In-Line Package
DS005803-1
Top View
Order Number DS3662J, DS3662N or DS3662WM
See NS Package Number J16A, N16A or M16B
Trapezoidal
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is a trademark of National Semiconductor Corp.
漏 1999 National Semiconductor Corporation
DS005803
www.national.com
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