The 33099 is designed to regulate the output voltage in dioderectified alternator charging systems common to automotive applications. The 33099 provides either an analog or digital fixed frequency duty cycle (ON/OFF ratio) control of an alternator's field current. Load Response Control (LRC) of the alternator field current is accomplished by selecting the duty cycle for prevailing engine conditions to eliminate engine speed hunting and vibrations caused by abrupt torque loading of the engine owing to sudden electrical loads being applied to the system at low engine RPM. Four LRC rates are selectable by connecting pins 7 and 8 to ground. The 33099 uses a feedback voltage to establish an alternator field current that is in harmony with system load currents. The output voltage is monitored by an internal voltage divider scheme and compared to an internal voltage ramp referenced to a bandgap voltage. This approach provides precision output voltage control over a wide range of temperature, electrical loads, and engine RPM. Features