Is there a specification for the input-signal rise time and fall time of the general-purpose logic ICs?
In the datasheet, the rise and fall times of general-purpose general-purpose logic ICs are specified in the operating ranges in which their functional operation is guaranteed. Use general-purpose logic ICs within the operating ranges to prevent a malfunction due to output oscillation etc.
If a slowly rising or falling signal (a low slew rate signal) is applied to an input, a current spike occurs during switching, causing VCC and GND bounce, which might result in output oscillation or a malfunction.
Use ICs with a Schmitt-trigger input for slowly changing inputs. However, in the case of excessively slowly changing inputs, even ICs with a Schmitt-trigger input might not be able to suppress noise on power supply or signal lines, resulting in output oscillation or instability.
The table-1 shows the rise and fall times of a typical IC*1 in each series.
Type |
Series Name |
CMOS Logic IC Series No. |
One-Gate Logic (L-MOS) Equivalents |
Operating Voltage Range VCC（V) |
Propagation Delay time *1 tpLH, tpHL (ns) |
Output Current*2, IOUT (mA) |
Rise and fall time ＠3.3 V |
Rise and fall time @5 V |
|---|---|---|---|---|---|---|---|---|
For 5-V Systems |
Standard |
3 to 18 |
200 |
±0.51 |
0~10 [μs/V]*4 |
0~5 [μs/V]*4 |
||
High Speed |
2 to 6 |
23 |
±4.0 or 6.0 |
0~1 [μs/V] |
0~500 [ns/V] |
|||
4.5 to 5.5 |
31 |
0~500 [ns/V] |
||||||
Advanced |
2 to 5.5 |
8.5 |
±24 |
0~100 [ns/V] |
0~20 [ns/V] |
|||
4.5 to 5.5 |
9.0 |
0~10 [ns/V] |
||||||
Very High Speed |
2 to 5.5 |
8.5 |
±8.0 |
0~100 [ns/V] |
0~20 [ns/V] |
|||
10 |
－ *3 |
－ *3 |
||||||
4.5 to 5.5 |
9.5 |
0~20 [ns/V] |
||||||
1.8 to 5.5 |
8.5 |
± 16 |
0~20 [ms/V] |
0~1 [ms/V] |
||||
For low-voltage Systems |
Low Voltage |
1.65 to 3.6 |
6.5 |
± 24 |
0~10 [ns/V] |
|||
| Very Low Voltage |
1.2 to 3.6 |
4.2 |
± 24 |
0~10 [ns/V] |
*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.
*3: Rise and fall times are not specified because the TC74VHC9 and 74VHC9 series provide Schmitt-trigger inputs.
*4:Rise and fall times are not specified in the datasheet. The values shown above should be considered only as a guide for creating a design.
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