1

2

4

6

8

19

11

13

15

17

3

5

7

9

12

14

16

18

1A1

1A2

1A3

1A4

1Y1

2A1

2A2

2A3

2A4

2Y1

1Y2

1Y3

1Y4

2Y2

2Y3

2Y4

1OE

2OE

SN74LVC240A

www.ti.com

SCAS293L – JANUARY 1993 – REVISED JULY 2014

9 Detailed Description

9.1 Overview

This device is organized as two 4-bit buffers/drivers with separate output-enable (OE) inputs. When OE is low,

the device passes data from the A inputs to the Y outputs. When OE is high, the outputs are in the high-

impedance state.

Inputs can be driven from either 3.3-V or 5-V devices. This feature allows the use of this device as a translator in

a mixed 3.3-V/5-V system environment.

To ensure the high-impedance state during power up or power down, OE should be tied to VCC through a pullup

resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

This device is fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs,

preventing damaging current backflow through the device when it is powered down.

9.2 Functional Block Diagram

Copyright © 1993–2014, Texas Instruments Incorporated

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