sy55854u Micrel Semiconductor, sy55854u Datasheet - Page 3

• Manufacturer Part Number: sy55854u
• Description: Sy55854u 2 X 2 Protection Crosspoint Switch
• Manufacturer: Micrel Semiconductor

Functional Description
Establishing Static Logic Inputs
The true pin of an input pair is internally biased to ground
through a 75kΩ resistor. The complement pin of an input
pair is internally biased halfway between V
by a voltage divider consisting of two 75kΩ resistors. In
this way, unconnected inputs appear as logic zeros. To
keep an input at static logic zero at V
inputs unconnected. For V
complement input to V
unconnected. To make an input static logic one, connect
the true input to V
unconnected. These are the only two safe ways to cause
inputs to be at a static value. In particular, no input pin
should be directly connected to ground. All NC (no
connect) pins should be unconnected.
Note:
1. X is either D0, D1, S0, or S1 input. /X is either /D0, /D1, /S0, or /S1
Micrel, Inc.
March 2007
input.
Figure 1. Hard Wiring a Logic “1”
Figure 2. Hard Wiring a Logic “0”
CC
, and leave the complement input
CC
and leave the true input
CC
≤ 3.0V, connect the
CC
> 3.0V, leave both
CC
(1)
(1)
and ground
3
Usage
SY55854U is very versatile. Tying its select inputs in
various ways varies its functionality. For example, tying the
select inputs together turns SY55854U into a redundant
distributor. Either input will be switched to both outputs
simultaneously. This is very useful in redundant backplane
applications. By cross-tying the select inputs, SY55854U
becomes a true crosspoint, selecting between “straight
through” and “cross connected” operation. Also, using the
select inputs independently, SY55854U functions as two
multiplexers. Setting the select inputs to static values turns
SY55854U into a dual buffer, or a fan-out buffer.
To make larger crosspoints, cascade SY55854U devices,
either in a tree, or in a Banyan structure, as appropriate for
your application.
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SY55854U