74LS645 Octal Bus Transceiver Tri-State


The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC. 74LS645 octal bus transceivers are designed for asynchronous two-way communication between data buses. The devices transmit data from the A bus to the B bus or from the B bus to the A bus depending upon the level at the direction control (DIR) input.

74LS645 Features

  • Designed for Asynchronous two-way Communication between Data Buses
  • Hysteresis at Bus Inputs Improves Noise Margins
  • 3-State Outputs Drive Bus Lines Directly
  • Operating Temperature up to 70°C
  • Standard TTL Switching Voltages

74LS645 Specifications

Supply Voltage4.75 – 5.25Vdc
Maximum Clock Frequency40Mhz
Power Dissipation2mW/gate @100kHz
Minimum Output Current8mA
Propagation Delay10nS
Fan Out (TTL Loads)20

74LS645 Pinout Diagram

74LS645 Pin Description

Pin NoPin NameDescription
1DIRDirection Control Pin
2A1Input/Output of Bus Transceiver A
3A2Input/Output of Bus Transceiver A
4A3Input/Output of Bus Transceiver A
5A4Input/Output of Bus Transceiver A
6A5Input/Output of Bus Transceiver A
7A6Input/Output of Bus Transceiver A
8A7Input/Output of Bus Transceiver A
9A8Input/Output of Bus Transceiver A
11B8Input/Output of Bus Transceiver B
12B7Input/Output of Bus Transceiver B
13B6Input/Output of Bus Transceiver B
14B5Input/Output of Bus Transceiver B
15B4Input/Output of Bus Transceiver B
16B3Input/Output of Bus Transceiver B
17B2Input/Output of Bus Transceiver B
18B1Input/Output of Bus Transceiver B
19G’Enable Pin
20VCCPositive Supply


  • transmit the data in the form of voice or data or video over the wireless medium

74LS645 Alternative Equivalent


Download 74LS645 Octal Bus Transceiver Tri-State Datasheet from the link given below.