Figure 6-8 Square Wave Generator

Figure 6-8 shows the application of the LMC6772 in a square wave generator circuit. The total hysteresis of the loop is set by R₁, R₂ and R₃. R₄ and R₅ provide separate charge and discharge paths for the capacitor C. The charge path is set through R₄ and D₁. So, the pulse width t₁ is determined by the RC time constant of R₄ and C. Similarly, the discharge path for the capacitor is set by R₅ and D₂. Thus, the time t₂ between the pulses can be changed by varying R₅, and the pulse width can be altered by R₄. The frequency of the output can be changed by varying both R₄ and R₅.

Figure 6-9 Time Delay Generator

The circuit shown above provides output signals at a prescribed time interval from a time reference and automatically resets the output when the input returns to ground. Consider the case of V_IN = 0. The output of comparator 4 is also at ground. This implies that the outputs of comparators 1, 2, and 3 are also at ground. When an input signal is applied, the output of comparator 4 swings high and C charges exponentially through R. This is indicated above. The output voltages of comparators 1, 2, and 3 swtich to the high state when V_C1 rises above the reference voltages V_A, V_B and V_C. A small amount of hysteresis has been provided to insure fast switching when the RC time constant is chosen to give long delay times.