STMicroelectronics has launched the L9918 automotive-grade alternator regulator, which ensures the stability of 12V automotive electrical systems with enhanced functionality.the regulator has a built-in MOSFET and a freewheeling diode. The MOSFET provides the alternator excitation current and the freewheeling diode is responsible for providing the rotor current when the excitation is turned off. The generator closed loop operation features Load Response Control (LRC) and Loop LRC Control to keep the output voltage constant as the overall power demand of the vehicle is changing.
The excitation MOSFET can deliver up to 13A to the coil, which is higher than the current handling capability of conventional voltage regulators, improving the system's response to fluctuations in power demand. In addition, because of the latest manufacturing process, the on-resistance RDS(on) of the new MOSFET is very low, which can greatly reduce the power dissipation while improving energy efficiency.
With on-chip non-volatile memory (NVM), customers can set the parameters of the L9918, including voltage set points, alternator characteristics, and more. Compatible with alternators with up to nine pole pairs, the regulator offers greater design flexibility than other regulators and can handle a variety of charging application scenarios. The L9918 also integrates a Local Interconnect Network (LIN) bus interface for easy connection to automotive electrical/electronic infrastructure to control the voltage regulator using an external Electronic Control Unit (ECU). ECU command settings include target voltage, read status and diagnostic information.
Safety and fail-safe features of the L9918 include self-start activation of the phase signal, which independently maintains the alternator voltage set point if the LIN bus is disconnected for any reason. When communication is restored, the regulator returns control to the ECU. Other built-in safety features include current limiting, overcurrent protection, and thermal protection, as well as thermal compensation that automatically adjusts the target voltage as system temperature changes. The L9918 complies with the VDA (Verband der Automobilindustrie) LIN alternator regulator specification, is certified to the AEC-Q 100 automotive electronics standard, complies with the ISO26262 standard, and reaches the ASIL-B automotive safety integrity level for use in functional safety systems.
