8 Detailed Description

8.1 Overview

The SN74HCS237 is a high speed silicon gate CMOS decoder well suited to memory address decoding or data

routing applications. It contains a single 3:8 decoder. All inputs include Schmitt-triggers allowing for slow input

transitions and providing additional noise margin.

The SN74HCS237 has three address select inputs (A2, A1, and A0). When the latch enable (LE) input is low, the

circuit functions as a normal one-of-eight decoder. When the latch enable (LE) input is high, the address latches

will maintain their previous states, regardless of any changes at the address select inputs.

Two strobe inputs (G 1 and G0) are provided to simplify cascading and to facilitate demultiplexing. When any

input strobe is active, all outputs are forced into the low state.

The demultiplexing function is accomplished by first using the select inputs to choose the desired output, and

then using one of the strobe inputs as the data input.

The outputs for the SN74HCS237 are normally low, and high when selected.

8.2 Functional Block Diagram

A

0

A

1

A

2

3-BIT

LATCH

LE

D

LE

Q

Q

D

LE

Q

Q

D

LE

Q

Q

D

LE

Q

Q

D

LE

Q

Q

D

LE

Q

Q

OUTPUT

ENABLE

Y

0

Y

1

Y

2

OE

1

OE

0

Y

3

Y

4

Y

5

Y

6

Y

7

3:8 DECODER

000

001

010

011

100

101

110

111

Figure 8-1. Logic Diagram (Positive Logic) for the SN74HCS237

8.3 Feature Description

8.3.1 Balanced CMOS Push-Pull Outputs

This device includes balanced CMOS push-pull outputs. 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 be limited to avoid damage due to overcurrent. The electrical and thermal limits defined in the

Absolute Maximum Ratings must be followed at all times.

Unused push-pull CMOS outputs should be left disconnected.

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SN74HCS237

SCLS834A – SEPTEMBER 2020 – REVISED JUNE 2021

Copyright © 2021 Texas Instruments Incorporated

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Product Folder Links: SN74HCS237