Power Management

L9779

L9779 - Multifunction Engine Management PMIC | STMicroelectronics

The L9779 from STMicroelectronics is a multifunction integrated circuit designed specifically for automotive engine management systems. Implemented in BCD6S technology, this power management IC integrates multiple functions including injector drivers, starter relay drivers, and power management features in a 64-pin HiQUAD package. It is engineered to operate reliably in the harsh automotive environment, supporting direct battery connection and key-switch control. A multifunction IC for engine management is a specialized power management device that consolidates several discrete functions—such as injector drivers, relay drivers, voltage regulators, and diagnostic interfaces—into a single package. In the system hierarchy, it sits between the engine control unit (ECU) microcontroller and the high-power actuators (fuel injectors, starter relays), translating low-power logic signals into high-current drive capabilities. This integration reduces board space, improves reliability, and simplifies the overall ECU design. Key features of the L9779 include four injector driver stages (OUT1-4) capable of driving high-current inductive loads, two starter relay drivers (OUT13 and OUT14), and a power latch/SEO (Start Enable Output) mode that allows direct key-switch shut-off access to critical outputs. The device operates from a wide battery voltage range, typically 6V to 28V, and includes protection features such as over-temperature shutdown, over-current limiting, and diagnostic feedback for fault detection. Technically, the L9779 is built on ST's BCD6S process, which combines Bipolar, CMOS, and DMOS transistors on a single die. This allows efficient high-current switching (DMOS) alongside precise analog control (bipolar) and low-power digital logic (CMOS). The device communicates with the ECU via a serial peripheral interface (SPI) in the L9779WD-SPI variant, enabling real-time diagnostics and configuration. The 64-pin HiQUAD package provides excellent thermal performance, with a low thermal resistance that supports continuous operation at high ambient temperatures typical of engine compartments. Typical applications include electronic fuel injection (EFI) systems, engine management units for gasoline and diesel engines, and automotive body control modules requiring high-current actuator drivers. The L9779 is also used in the ST SPC572L MCU-based EFI solution, where it pairs with the SPC572L64F2 microcontroller to form a complete engine control platform. When designing with the L9779, ensure adequate PCB copper area for heat dissipation, especially when driving multiple injectors simultaneously. The power latch mode must be configured correctly to meet the system's safety requirements, and the SPI interface (if used) should be properly terminated to avoid communication errors.