The maximum clock frequency of the SN54LS74AJ is 35 MHz.
To ensure proper initialization, connect the preset (PRE) and clear (CLR) inputs to VCC through a 1 kΩ resistor and a 0.01 μF capacitor to ground, respectively.
The recommended operating voltage range for the SN54LS74AJ is 4.5 V to 5.5 V.
No, the SN54LS74AJ is not recommended for use in 3.3 V systems. It is designed to operate at 5 V.
The preset (PRE) and clear (CLR) inputs should be driven asynchronously, and the clock (CLK) input should be low when these inputs are active.