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.
Type |
Series Name |
CMOS Logic IC Series No. |
One-Gate Logic ( L-MOS ) Equivalents |
Operating Voltage Range |
Output current*2, IOUT (mA) |
tpLH ,tpHL( ns )*1 CL = 50pF |
Maximum Operating Frequency (Calculated value) (MHz) |
|---|---|---|---|---|---|---|---|
For 5-V Systems |
Standard |
3 to 18 |
±0.51 |
200 |
3 |
||
High Speed |
2 to 6 |
±4.0 or ±6.0 |
23 |
22 |
|||
4.5 to 5.5 |
31 |
17 |
|||||
Advanced |
- |
2 to 5.5 |
± 24 |
8.5 |
59 |
||
4.5 to 5.5 |
9.0 |
56 |
|||||
Very High Speed |
2 to 5.5 |
± 8.0 |
8.5 |
59 |
|||
10 |
50 |
||||||
9.5 |
53 |
||||||
4.5 to 5.5 |
8.5 |
59 |
|||||
For low voltage Systems |
Low Voltage |
1.8 to 5.5 |
± 16 |
6.5 |
77 |
||
| Very Low Voltage | 1.65 to 3.6 |
± 24 |
4.2 |
114 |
*1: Maximum propagation delay time of typical ICs (TC4001, TC74HC244, TC74HCT244, TC74AC244, TC74ACT244, 74VHC244, 74VHC9541 (An-Yn), VHCT244, VHCV244, 74LCX244, and TC74VCX244) at -40 to 85 °C, except for the TC4001 for which the maximum propagation delay time at 25 °C is shown.
*2: Those output current values are from DC Characteristics table of the datasheet. In addition, absolute maximum ratings also specify the current.
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