DS3896/DS3897 BTL Trapezoidal Transceivers
OBSOLETE
DS3896/DS3897
BTL Trapezoidal™ Transceivers
General Description
These advanced transceivers are specifically designed to
overcome problems associated with driving a densely popu-
lated backplane, and thus provide significant improvement in
both speed and data integrity. Their low output capacitance,
low output signal swing and noise immunity features make
them ideal for driving low impedance buses with minimum
power consumption.
The DS3896 is an octal high speed schottky bus transceiver
with common control signals, whereas the DS3897 is a quad
device with independent driver input and receiver output pins.
The DS3897 has a separate driver disable for each driver and
is, therefore, suitable for arbitration lines. The separate driver
disable pins (En) feature internal pull ups and may be left open
if not required. On the other hand, the DS3896 provides high
package density for data/address lines.
The open collector drivers generate precise trapezoidal
waveforms, which are relatively independent of capacitive
loading conditions on the outputs. This significantly reduces
noise coupling to adjacent lines. In addition, the receivers use
a low pass filter in conjunction with a high speed comparator,
to further enhance the noise immunity and provide equal re-
jection to both negative and positive going noise pulses on
the bus.
To minimize bus loading, these devices also feature a schot-
tky diode in series with the open collector output that isolates
the driver output capacitance in the disabled state. The output
low voltage is typically “1V” and the output high level is in-
tended to be 2V. This is achieved by terminating the bus with
a pull up resistor to 2V at both ends. The device can drive an
January 6, 1996
equivalent DC load of 18.5Ω
(or
greater) in the above config-
uration.
These signalling requirements, including a 1 volt signal swing,
low output capacitance and precise receiver thresholds are
referred to as Bus Transceiver Logic (BTL).
Features
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8 bit DS3896 transceiver provides high package density
■
4 bit DS3897 transceiver provides separate driver input
■
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■
■
■
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and receiver output pins
BTL compatible
Less than 5 pF output capacitance for minimal bus loading
1 Volt bus signal swing reduces power consumption
Trapezoidal driver waveforms (t
r
, t
f
≃ 6 ns typical) reduce
noise coupling to adjacent lines
Temperature insensitive receiver thresholds track the bus
logic high level to maximize noise immunity in both high
and low states
Guaranteed A.C. specifications on noise immunity and
propagation delay over the specified temperature and
supply voltage range
Open collector driver output allows wire-or connection
Advanced low power schottky technology
Glitch free power up/down protection on driver and
receiver outputs
TTL compatible driver and control inputs and receiver
outputs
Trapezoidal™ is a trademark of National Semiconductor Corporation.
© 2009 National Semiconductor Corporation
8510
Print Date/Time: 2009/07/20 16:46:54
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8510 Version 6 Revision 2
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