How can I find the maximum operating frequency of a general-purpose logic IC?
If the seat of the general-purpose logic IC does not contain a description of the maximum operating frequency, the propagation delay time (tpLH, tpHL) can be roughly estimated using the following formula. Maximum operating frequency ≒ 1/ (tpLH + tpHL)
Table 1 shows the propagation delay times of representative products in each series and the results of the above formula.
Propagation delay times depend on the IC function. For ICs other than the typical ICs shown below, see the datasheet for propagation delay times and use them to calculate the maximum operating frequency. Propagation delay times also depend on wire lengths and loads in actual applications.
The maximum operating frequencies shown below should be considered only as a guide. Be sure to verify that the ICs you have selected operate properly under actual usage conditions.
类型 |
系列名称 |
CMOS逻辑IC系列型号 |
单门逻辑（L-MOS）等效电路 |
工作电压范围 VCC（V） |
输出电流*2 IOUT（MA） |
tpLH ,tpHL( ns )*1 CL＝50pF |
最大工作频率计算结果（MHz） |
|---|---|---|---|---|---|---|---|
适用于5V系统 |
标准型 |
3至18 |
±0.51 |
200 |
3 |
||
高速型 |
2至6 |
±4.0或6.0 |
23 |
22 |
|||
4.5至5.5 |
31 |
17 |
|||||
进阶型 |
- |
2至5.5 |
±24 |
8.5 |
59 |
||
4.5至5.5 |
9.0 |
56 |
|||||
超高速型 |
2至5.5 |
±8.0 |
8.5 |
59 |
|||
10 |
50 |
||||||
9.5 |
53 |
||||||
4.5至5.5 |
8.5 |
59 |
|||||
适用于低电压系统 |
低压型 |
1.8至5.5 |
±16 |
6.5 |
77 |
||
超低压型 |
1.65至3.6 |
±24 |
4.2 |
114 |
*1：典型IC（TC4001，TC74HC244，TC74HCT244，TC74AC244，TC74ACT244，74VHC244，74VHC9541（An-Yn），VHCT244，VHCV244，74LCX244和TC74VCX244）在-40至85°C时的最大传输延迟时间，但TC4001显示的是25°C时最大传输延迟时间。
*2：这些输出电流值来自数据表的直流特性表。此外，还指定了绝对最大额定值。
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