SN74CBT3251_15 Datasheet, PDF (7/25 Pages) Texas Instruments – FET Multiplexer and Demultiplexer

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8 Detailed Description
SN74CBT3251
SCDS019M – MAY 1995 – REVISED DECEMBER 2015
8.1 Overview
The SN74CBT3251 device is a single 8-channel multiplexer with three binary control inputs, S₀, S₁, and S₂ and
an OE (output enable, active low) input. The three binary signals select 1 of 8 channels to be turned on, and
connect one of the 8 inputs to the output.
When they are used as demultiplexers, the CHANNEL IN/OUT terminals (B) are the outputs and the COMMON
OUT/IN terminal (A) is the input.
8.2 Functional Block Diagram
5
A
4
B1
3
B2
2
B3
1
B4
15
B5
14
B6
13
B7
12
B8
7
OE
11
S0
10
S1
9
S2
Figure 3. Logic Diagram (Positive Logic)
8.3 Feature Description
The SN74CBT3251 1-of-8 FET multiplexers and demultiplexers can accept a wide range of analog signal levels
from 0 V to 5 V. It has low Ron resistance, typically 5-Ω for V_CC = 5 V which allows very little signal loss through
the switch. Binary address decoding on chip makes channel selection easy.
8.4 Device Functional Modes
Table 1 lists the functional modes of the SN74CBT3251.
Table 1. Function Table (Each Multiplexer and Demultiplexer)
INPUTS
FUNCTION
OE
S2
S1
S0
L
L
L
L
A port = B1 port
L
L
L
H
A port = B2 port
L
L
H
L
A port = B3 port
L
L
H
H
A port = B4 port
L
H
L
L
A port = B5 port
L
H
L
H
A port = B6 port
L
H
H
L
A port = B7 port
L
H
H
H
A port = B8 port
H
X
X
X
Disconnect
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