MC3325

MC3325 is a monolithic automotive voltage regulator integrated circuit developed by Motorola Semiconductor for use in alternator charging systems. The device is specifically designed to control the output of an automotive alternator by regulating the field current through an external NPN Darlington power transistor, maintaining stable battery charging voltage across varying operating conditions.

MC3325

The IC monitors battery voltage through dedicated battery sense inputs and adjusts the alternator field current accordingly. If the sensed voltage rises above the programmed threshold, the regulator reduces field current to prevent overcharging. The device also incorporates overvoltage protection, battery sense loss detection, and configurable temperature compensation to maintain appropriate charging characteristics as battery temperature changes.

MC3325

Temperature compensation is implemented using an external diode string, allowing designers to tailor the charging voltage coefficient for different battery chemistries. The IC also includes an adjustable output driver stage capable of controlling an external high-current transistor used to drive the alternator field winding.

MC3325

The MC3325 was commonly used in automotive alternator regulator modules and other vehicle electrical systems requiring controlled battery charging. The device is supplied in a 14-pin plastic DIP package (Motorola Case 646) and is rated for operation across the automotive temperature range of −40 °C to +85 °C.