The CS3341 IC’s series from Cherry Semiconductor are designed for use in alternator charging system particularly the
CS3341 and CS3351. This device drives an external power Darlington for controlling the alternator field current and provides 3-phase alternators-the voltage regulation for automotive.
The circuit diagram shows you a typical application of The CS3341 IC’s series. The oscillator frequency is set by an external capacitor connected between OSC and ground. According to the datasheet, the alternator voltage is sensed at Terminal A
via the resistor divider network R1/R2 on the Sense pin of the IC.
Voltage at sense pin means the duty cycle for the regulator and adjusted
by potentiometer R2. The Lamp pin goes high when an overvoltage is
detected on sense pin and make the darlington lamp drive transistor to switch on and pull current through the lamp.
Alternator Voltage Regulator has features such Short Circuit
Protection, 80V Load Dump, Temperature Compensated Regulation Voltage,
and Shorted Field Protection Duty Cycle, Self Clearing in addition of Drives NPN Darlington.
Please read completely Darlington Driver Device in Alternator Charging System in the CS3341 series datasheet (source: cherrycorp.com)