The ’HC257 and ’HCT257 are quad 2-input multiplexers which select four bits of data from two sources under the control of a common Select Input (S). The Output Enable input (OE\) is active LOW. When OE\ is HIGH, all of the outputs (1Y-4Y) are in the high impedance state regardless of all other input conditions.

Moving data from two groups of registers to four common output buses is a common use of the 257. The state of the Select input determines the particular register from which the data comes. It can also be used as a function generator.

• Buffered Inputs
• Typical Propagation Delay (In to Output) = 12ns at VCC = 5V, CL = 15pF, TA = 25°C
• Fanout (Over Temperature Range)
  • Standard Outputs...10 LSTTL Loads
  • Bus Driver Outputs...15 LSTTL Loads
• Wide Operating Temperature Range...–55°C to 125°C
• Balanced Propagation Delay and Transition Times
• Significant Power Reduction Compared to LSTTL Logic ICs
• HC Types
  • 2V to 6V Operation
  • High Noise Immunity: NIL = 30%, NIH = 30% of VCC at VCC = 5V
• HCT Types
  • 4.5V to 5.5V Operation
  • Direct LSTTL Input Logic Compatibility, VIL = 0.8V (Max), VIH = 2V (Min)
  • CMOS Input Compatibility, Il 1μA at VOL, VOH

Data sheet acquired from Harris Semiconductor

• Technology Family
• HC
• Function
• Digital Multiplexer
• Configuration
• 2:1
• Number of channels (#)
• 4
• Operating temperature range (C)
• -55 to 125
• Rating
• Catalog

CD74HC257的完整型号有：CD74HC257E、CD74HC257M、CD74HC257M96，以下是这些产品的关键参数及官网采购报价：

CD74HC257E，工作温度：-55 to 125，封装：PDIP (N)-16，包装数量MPQ：25个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：NIPDAU，TI官网CD74HC257E的批量USD价格：.285（1000+）

CD74HC257M，工作温度：-55 to 125，封装：SOIC (D)-16，包装数量MPQ：40个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网CD74HC257M的批量USD价格：.296（1000+）

CD74HC257M96，工作温度：-55 to 125，封装：SOIC (D)-16，包装数量MPQ：2500个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网CD74HC257M96的批量USD价格：.251（1000+）

14-24-LOGIC-EVM — 支持 14 到 24 引脚 PW、DB、D、DW、NS、DYY 和 DGV 封装的通用逻辑 EVM

该 EVM 设计用于支持采用 14 至 24 引脚 D、DW、DB、NS、PW、DYY 或 DGV 封装的任何逻辑器件。