CD74HC257是TI公司的一款解码器/编码器/多路复用器产品，CD74HC257是具有同向三态输出的高速 CMOS 逻辑四路 2 输入多路复用器，本页介绍了CD74HC257的产品说明、应用、特性等，并给出了与CD74HC257相关的TI元器件型号供参考。
CD74HC257 - 具有同向三态输出的高速 CMOS 逻辑四路 2 输入多路复用器 - 解码器/编码器/多路复用器 - 特殊逻辑 - TI公司（Texas Instruments，德州仪器）
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
