IAC Motor Driver - Block K


        This circuit is designed to drive the Ford style IAC motor that is include with the Edelbrock/Weber Pro-Flo EFI system. These Ford style motors are a solenoid operated with an output shaft that is configured in a tapered valve arrangement.  As this solenoid oscillates back and forth you can change the duty cycle of the pulse train fed to it.  This causes the average shaft position to spend more or less time in a positions to port more or less air through its valve body.  This air path bypasses air around the main throttle butterfly plates controlling engine idle speed.
        The VN14NV04 is a fully auto protected power MOSFET.  It can protect itself from over current and over power conditions.  It also contains its own internal clamping diode that is why you see none here.  Because it is a smart device you don't have the usual problem of driving the gate capacitance of a normal FET.  The 74HCT14 just provides a good buffered edge to the device.