These 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. The enable input (G) can be used to disable the device so the buses are effectively isolated.

The -1 versions of the SN74LS640 thru SN74LS642, SN74LS644, and SN74LS645 are identical to the standard versions except that the recommended maximum I_OL is increased to 48 milliamperes. There are no -1 versions of the SN54LS640 thru SN54LS642, SN54LS644, and SN54LS645.

The SN54LS640 thru SN54LS642, SN54LS644, and SN54LS645 are characterized for operation over the full military tempearture range of –55°C to 125°C. The SN74LS640 thru SN74LS642, SN74LS644, and SN74LS645 are characterized for operation from 0°C to 70°C.

• SN74LS64X-1 Versions Rated at IOL of 48 mA
• Bi-directional Bus Transceivers in High-Density 20-Pin Packages
• Hysteresis at Bus Inputs Improves Noise Margins
• Choice of True or Inverting Logic
• Choice of 3-State or Open-collector Outputs

• IOL (Max) (mA)
• 12
• IOH (Max) (mA)
• -12
• Technology Family
• LS
• Rating
• Military
• Operating temperature range (C)
• -55 to 125

SN54LS640的完整型号有：84161012A、8416101RA、SN54LS640J、SNJ54LS640FK、SNJ54LS640J，以下是这些产品的关键参数及官网采购报价：

84161012A，工作温度：-55 to 125，封装：LCCC (FK)-20，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网84161012A的批量USD价格：27.106（1000+）

8416101RA，工作温度：-55 to 125，封装：CDIP (J)-20，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网8416101RA的批量USD价格：12.403（1000+）

SN54LS640J，工作温度：-55 to 125，封装：CDIP (J)-20，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网SN54LS640J的批量USD价格：10.187（1000+）

SNJ54LS640FK，工作温度：-55 to 125，封装：LCCC (FK)-20，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网SNJ54LS640FK的批量USD价格：27.106（1000+）

SNJ54LS640J，工作温度：-55 to 125，封装：CDIP (J)-20，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网SNJ54LS640J的批量USD价格：12.403（1000+）