8 Detailed Description

8.1 Overview

The SN74HCS251 is a data selector/multiplexer containing full binary decoding to select 1-of-8 data sources and

features strobe-controlled complementary 3-state outputs.

The 3-state outputs can interface with and drive data lines of bus-organized systems. With all but one of the

common outputs disabled (in the high-impedance state), the low impedance of the single enabled output drives

the bus line to a high or low logic level. Both outputs are controlled by the output-enable (OE) input. The outputs

are disabled when OE is high.

8.2 Functional Block Diagram

000

001

010

011

100

101

110

111

A

B

C

CBA

D0

D1

D2

D3

D4

D5

D6

D7

Y

W

OE

Figure 8-1. Logic Diagram (Positive Logic) for SN74HCS251

8.3 Feature Description

8.3.1 Balanced CMOS 3-State Outputs

This device includes balanced CMOS 3-State outputs. The three states that these outputs can be in are driving

high, driving low, and high impedance. The term "balanced" indicates that the device can sink and source similar

currents. The drive capability of this device may create fast edges into light loads so routing and load conditions

should be considered to prevent ringing. Additionally, the outputs of this device are capable of driving larger

currents than the device can sustain without being damaged. It is important for the output power of the device to

www.ti.com

SN74HCS251

SCLS841 – SEPTEMBER 2020

Copyright © 2020 Texas Instruments Incorporated

Submit Document Feedback

9

Product Folder Links: SN74HCS251