JAJSM49E January 1998 – May 2021 CD54HC74 , CD74HC74
PRODUCTION DATA
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Toggle switches are typically large, mechanically complex and relatively expensive. It is desirable to use a momentary switch instead because they are small, mechanically simple and low cost. Some systems require a toggle switch's functionality but are space or cost constrained and must use a momentary switch instead.
If the data input (D) of the D-type flip-flop is tied to the inverted output ( Q), then each clock pulse will cause the value at the output (Q) to toggle. The momentary switch can be debounced and connected through a Schmitt-trigger buffer to the clock input (CLK) to toggle the output.
This application also utilizes a power-on reset circuit to ensure that the output always starts in the LOW state when power is applied.