74HC245八总线收发器（三态、原码）
·三态输出直接驱动总线；
·PNP 输入减小了直流负载；
·输入滞后电压可改善噪声容限
这种八位总线收发器是为数据总线间进行异步两路通讯而设计的。采用控制
功能可以尽量减少外部定时电路的要求。
这种电路可以将数据从A 总线传送到B 总线，也可将数据从B 总线传送到
A 总线，具体传送方向要看方向控制（DIR）输入的逻辑电平而定。可以用使能
输入来禁止这种电路，使总线之间能有效地隔离。
TRUTH TABLE真值表
|
Control Inputs |
Operation 运行 |
|
| G | DIR | |
| L | L | B 数据到A 总线 |
| L | H | A 数据到B 总线 |
| H | X | 隔开 |
H=高电平 L=低电平 ×=不定
| Absolute Maximum Ratings绝对最大额定值 | |
| Supply Voltage电源电压(VCC) | -0.5 to -7.0V |
| DC Input Voltage DIR and G pins (VIN) 直流输入电压方向和G引脚（输入电压） | -1.5 to VCC -1.5V |
| DC Input/Output Voltage (VIN, VOUT)直流输入/输出电压 | -0.5 to VCC -0.5V |
| Clamp Diode Current 钳位二极管电流(ICD) | ±20 mA |
| DC Output Current直流输出电流，每个引脚（输出） | ±35 mA |
| DC VCC or GND Current, per pin (ICC) | ±70 mA |
| Storage Temperature Range 储存温度范围(TSTG) | -65℃ to -150℃ |
| Power Dissipation (PD)功耗 | |
| (Note 3) | 600 mW |
| S.O. Package only | 500 mW |
| Lead Temperature (TL) (Soldering 10 seconds) | 260℃ |
Note 1: Maximum Ratings are those values beyond which damage to the
device may occur.
Note 2: Unless otherwise specified all voltages are referenced to ground.
Note 3: Power Dissipation temperature derating — plastic “N” package:
12 mW/℃ from 65℃ to 85℃.
| Recommended Operating Conditions建议操作条件 | |||
| 参数 | 最小 | 最大 | 单位 |
| Supply Voltage电源电压(VCC) | 2 | 6 | V |
| DC Input or Output Voltage (VIN, VOUT)直流输入输出电压 | 0 | VCC | V |
| Operating Temperature Range工作温度范围 (TA) | -40 | -85 | ℃ |
| Input Rise/Fall Times输入上升/下降时间 | |||
| (tr,tf) VCC=2.0V | - | 1000 | ns |
| VCC=4.5V | - | 500 | ns |
| VCC=6.0V | - | 400 | ns |
DC SPECIFICATIONS直流电气规格
| Symbol 符号 | Parameter 参数 | Conditions 条件 | VCC | TA=25℃ | TA=-40 to 85℃ | TA=-55 to 125℃ | UNIT 单位 | |
| 典型 |
Guaranteed Limits保证界限 |
|||||||
| VIH | Minimum High Level Input Voltage输入高电平电压 | - | 2.0V | - | 1.5 | 1.5 | 1.5 | V |
| 4.5V | - | 3.15 | 3.15 | 3.15 | ||||
| 6.0V | - | 4.2 | 4.2 | 4.2 | ||||
| VIL | Maximum LOW Level Input Voltage 输入低电平电压 | - | 2.0V | - | 0.5 | 0.5 | 0.5 | V |
| 4.5V | - | 1.35 | 1.35 | 1.35 | ||||
| 6.0V | - | 1.8 | 1.8 | 1.8 | ||||
| VOH | Minimum HIGH Level Output Voltage输出高电平电压 | VIN=VIH or VIL |IOUT| ≤ 20μA | 2.0V | 2.0 | 1.9 | 1.9 | 1.9 | V |
| 4.5V | 4.5 | 4.4 | 4.4 | 4.4 | ||||
| 6.0V | 6.0 | 5.9 | 5.9 | 5.9 | ||||
| VINVIH or VIL | ||||||||
| |IOUT| ≤ 6.0mA | 4.5V | 4.2 | 3.98 | 3.84 | 3.7 | V | ||
| |IOUT| ≤ 7.8mA | 6.0V | 5.7 | 5.48 | 5.34 | 5.2 | |||
| VOL | Maximum LOW Level Output Voltage输出低电平电压 | VIN=VIH or VIL|IOUT| ≤ 20μA | 2.0V | 0 | 0.1 | 0.1 | 0.1 | V |
| 4.5V | 0 | 0.1 | 0.1 | 0.1 | ||||
| 6.0V | 0 | 0.1 | 0.1 | 0.1 | ||||
| VINVIH or VIL | ||||||||
| |IOUT| ≤ 6.0mA | 4.5V | 0.2 | 0.26 | 0.33 | 0.4 | V | ||
| |IOUT| ≤ 7.8mA | 6.0V | 0.2 | 0.26 | 0.33 | 0.4 | |||
| IIN | Input Leakage Current输入漏电流 (G and DIR) | VIN=VCC to GND | 6.0V | - | ±0.1 | ±1.0 | ±1.0 | μA |
| IOZ | Maximum 3-STATE Output Leakage Current最多3态输出漏电流 | VOUT=VCC or GND Enable G=VIH | 6.0V | - | ±0.5 | ±5.0 | ±10 | μA |
| ICC | Maximum Quiescent Supply Current电源电流 | VIN=VCC or GND IOUT=0μA | 6.0V | - | 8.0 | 80 | 160 | μA |
AC Electrical Characteristics VCC=5V, TA=25℃, tr= tf =6ns交流电气特性
| Symbol 符号 | Parameter 参数 | Conditions 条件 | 典型 | Guaranteed Limit | UNIT 单位 |
| tPHL, tPLH | Maximum Propagation Delay传播延迟 | CL=45pF | 12 | 17 | ns |
| tPZH, tPZL | Maximum Output Enable Time最大输出启用时间 | RL=1k CL=45pF | 24 | 35 | ns |
| tPHZ, tPLZ | Maximum Output Disable Time最大输出禁止时间 | RL=1k CL=5pF | 18 | 25 | ns |
AC Electrical Characteristics VCC=2.0V to 6.0V, CL=50 pF, t r= tf =6ns 交流电气特性
| Symbol 符号 | Parameter 参数 | Conditions 条件 | VCC | TA 25℃ | TA=-40 to 85℃ | TA=-55 to 125℃ | UNIT 单位 | ||
| 典型 | Guaranteed Limits 保证界限 | ||||||||
| tPHL, tPLH | Maximum Propagation Delay 最大传输延迟 | CL=50pF | 2.0V | 31 | 90 | 113 | 135 | ns | |
| CL=150pF | 2.0V | 41 | 96 | 116 | 128 | ||||
| CL=50pF | 4.5V | 13 | 18 | 23 | 27 | ||||
| CL=150pF | 4.5V | 17 | 22 | 28 | 33 | ||||
| CL=50pF | 6.0V | 11 | 15 | 19 | 23 | ||||
| CL=150pF | 6.0V | 14 | 19 | 23 | 28 | ||||
| tPZH, tPZL | Maximum Output Enable Time 最大输出启用时间 | RL=1k | CL=50pF | 2.0V | 71 | 190 | 240 | 285 | ns |
| CL=150pF | 2.0V | 81 | 240 | 300 | 360 | ||||
| CL=50pF | 4.5V | 26 | 38 | 48 | 57 | ||||
| CL=150pF | 4.5V | 31 | 48 | 60 | 72 | ||||
| CL=50pF | 6.0V | 21 | 32 | 41 | 48 | ||||
| CL=150pF | 6.0V | 25 | 41 | 51 | 61 | ||||
| tPHZ, tPLZ | Maximum Output Disable Time最大输出禁止时间 | RL=1k CL=50pF | 2.0V | 39 | 135 | 169 | 203 | ns | |
| 4.5V | 20 | 27 | 34 | 41 | |||||
| 6.0V | 18 | 23 | 29 | 34 | |||||
| tTLH, tTHL | Output Rise and Fall Time输出上升和下降时间 | CL=50pF | 2.0V | 20 | 60 | 75 | 90 | ns | |
| 4.5V | 6 | 12 | 15 | 18 | |||||
| 6.0V | 5 | 10 | 13 | 15 | |||||
| CPD | Power DissipationCapacitance (Note 5)功耗电容（注5 ） | G=VIL | - | 50 | - | - | - | pF | |
| G=VIH | - | 5 | - | - | - | ||||
| CIN | Maximum Input Capacitance最大输入电容 | - | - | 5 | 10 | 10 | 10 | pF | |
| CIN/OUT | Maximum Input/Output Capacitance, A or B 最大输入/输出电容， A或B | - | - | 15 | 20 | 20 | 20 | pF | |
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图1 74HC245 内部电路图 |
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图2 74HC245逻辑图 |
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图3 应用电路-片选存储器，译码和A D转换器与DSP电路 |
