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74240 Octal Buffers and Line Drivers With 3-State Outputs

Octal Buffers and Line Drivers With 3-State Outputs

Table of Contents

The 74240 provides Octal Buffers and Line Drivers With 3-State Outputs.

They are organized as two 4-bit buffers and drivers with separate output-enable (G) inputs. When G is low, the device passes data from the A inputs to the Y outputs. When G 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 and 5-V system environment. To ensure the high-impedance state during power up or power down, G must be tied to VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

Function table
Inputs Output
G An Yn
L L H
L H L
H L Z
H H Z
Pin I/O Description
No Name
1 1G I Channel 1 output enable
2 1A1 I Channel 1 A side 1
3 2Y4 O Channel 2 Y side 4
4 1A2 I Channel 1 A side 2
5 2Y3 O Channel 2 Y side 3
6 1A3 I Channel 1 A side 3
7 2Y2 O Channel 2 Y side 2
8 1A4 I Channel 1 A side 4
9 2Y1 O Channel 2 Y side 1
10 GND Ground
11 2A1 I Channel 2 A side 1
12 1Y4 O Channel 1 Y side 4
13 2A2 I Channel 2 A side 2
14 1Y3 O Channel 1 Y side 3
15 2A3 I Channel 2 A side 3
16 1Y2 O Channel 1 Y side 2
17 2A4 I Channel 2 A side 4
18 1Y1 O Channel 1 Y side 1
19 2G I Channel 2 Output Enable
20 VCC Power supply