STEPPER_MOTOR_PULSE_GENERATOR

Published:2009/6/24 2:59:00 Author:May | From:SeekIC

When the switch is in its normally closed (NC) position, capacitors C1 and C2 are held discharged by diodes Dl and D2. Switching off transistor Q1 inhibits the voltage-controlled oscillator of the PLL. The two inputs and, hence, the output of the EX-OR gate (phase comparator 1) ofthe PLL remain at the logic 0 level.When the pushbutton is pressed, C1 and C2 are allowed to charge via resistors R1 and R2. The VCO is enabled only after a time delay (≈0.5 second) set by R1, R3, and C1. During this delay period, the EX-OR gate output follows the logic level at the switch output. As a result, one-shot pulses can be generated by pressing the pushbutton, then releasing it within 0.5 second. R5 provides the switch-debouncing function.If the pushbutton is pressed for more than 0.5 second, the VCO is enabled. The rising voltage at the control input (pin 9) causes a linear increase in VCO frequency and thus accelerates the step-per motor. Releasing the pushbutton discharges C1 and C2 and inhibits the VCO.



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