FAQ: Logic and Voltage Translation > Input Parameters >> Current FAQ
This question comes up fairly often because the HCS logic family is specified only at 2V, 4.5V, and 6V.
The following min / max values are interpolated from the datasheet tables, and thus are guaranteed by the datasheet specifications. Typical values are not guaranteed, however they are good estimates of performance under normal operating conditions.
HCS Family Electrical Characteristics
| PARAMETER | TEST CONDITIONS | VCC | MIN | TYP | MAX | UNIT | |
| VT+ | Positive switching threshold | 3.3 V | 1.22 | 1.93 | 2.36 | V | |
| VT- | Negative switching threshold | 3.3 V | 0.61 | 1.28 | 1.62 | V | |
| ΔVT | Hysteresis (VT+ - VT-) | 3.3 V | 0.3 | 0.65 | 1.21 | V | |
| VOH | High-level output voltage | IOH = -20 uA | 3.3 V | 3.2 | 3.298 | V | |
| IOH = -4 mA | 3.3 V | 3.14 | |||||
| VOL | Low-level output voltage | IOL = 20 uA | 3.3 V | 0.002 | 0.1 | V | |
| IOL = 4 mA | 3.3 V | 0.12 | |||||
| PARAMETER | VCC | MIN | TYP | MAX | UNIT | |
| fmax | Max switching frequency (HCS74) | 3.3 | 32 | 64 | MHz | |
| fmax | Max switching frequency (HCS165) | 3.3 | 83 | 91 | MHz | |
| fmax | Max switching frequency (HCS595) | 3.3 | 40 | 74 | MHz | |
Timing specifications are specific to each device -- please use linear interpolation for any timing parameters that need to be checked at 3.3V.
This related FAQ includes an Excel calculator to help speed this process: