L9779 - Multifunction Engine Management PMIC | STMicroelectronics
MPN: L9779 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $12.5 | $12.50 |
| 10 | $11.25 | $112.50 |
| 100 | $10 | $1,000.00 |
| 500 | $9 | $4,500.00 |
| 1,000 | $8.1 | $8,100.00 |
L9779 Overview
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.
Drop-in alternatives for L9779 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with L9779 (same form factor and footprint) — differing in Package, Technology.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
L9779WD-SPI-TR
✅ Drop-In✓ In Stock
$14.5 / Unit
View Datasheet →L9779WD-SPI-TR
✅ Drop-In✓ In Stock
$14.5 / Unit
View Datasheet →L9779 Specifications
| Function | Multifunction IC for engine management system |
| Technology | BCD6S |
| Package | 64-HiQUAD |
| Injector Driver Stages | 4 (OUT1-4) |
| Starter Relay Drivers | 2 (OUT13, OUT14) |
| Power Latch Mode | Yes |
| SEO (Start Enable Output) Mode | Yes |
| SPI Interface | Yes (L9779WD-SPI variant) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
| Automotive Grade | Yes (designed for automotive environment) |
L9779 Pin Configuration
| Pin 1 | OUT1 — Injector driver output 1 |
| Pin 2 | OUT2 — Injector driver output 2 |
| Pin 3 | OUT3 — Injector driver output 3 |
| Pin 4 | OUT4 — Injector driver output 4 |
| Pin 13 | OUT13 — Starter relay driver output 13 |
| Pin 14 | OUT14 — Starter relay driver output 14 |
| Pin 32 | VCC — Power supply |
| Pin 33 | GND — Ground |
| Pin 64 | KEY — Key-switch input for power latch |
Typical Applications
L9779 is suitable for 6 applications: Electronic Fuel Injection (EFI) Systems, Engine Management Units (EMU), Automotive Body Control Modules, Start-Stop Systems, Motorcycle Engine Control, Small Engine Management (Generators, Marine).
Electronic Fuel Injection (EFI) Systems
The L9779 is a core component in EFI systems, driving fuel injectors and starter relays. It integrates four injector drivers (OUT1-4) and two starter relay drivers (OUT13, OUT14), enabling precise fuel delivery control. In a typical EFI setup, the L9779 receives commands from an ECU microcontroller like the SPC572L64F2 and drives the injectors with high-current pulses. The power latch mode allows direct key-switch shut-off for safety. Compared to discrete solutions, the L9779 reduces board space and improves reliability by integrating protection and diagnostic features. For a 4-cylinder engine, all four injector drivers can be used simultaneously, with each driver capable of handling the inductive load of a standard injector. The BCD6S technology ensures efficient high-current switching with low power dissipation, making it suitable for continuous operation in engine compartments.
Recommended
Engine Management Units (EMU)
In engine management units, the L9779 consolidates multiple actuator drivers and power management functions. It handles injector control, starter relay activation, and provides diagnostic feedback to the ECU. The device's BCD6S technology allows integration of high-current DMOS outputs with precise analog control and low-power digital logic. In a typical EMU, the L9779 is placed on the power board, receiving logic-level signals from the microcontroller and driving high-current loads. The 64-pin HiQUAD package offers good thermal performance, essential for the high ambient temperatures under the hood. The power latch and SEO modes provide flexible control for safety-critical functions. Compared to using separate driver ICs, the L9779 simplifies the design, reduces component count, and improves overall system reliability.
Recommended
Automotive Body Control Modules
The L9779 can be used in body control modules that require high-current actuator drivers, such as relay drivers for lights, wipers, or other loads. Its two starter relay drivers (OUT13, OUT14) can be repurposed for general relay control. The device's wide operating voltage range and automotive-grade design make it suitable for direct battery connection. In a body control module, the L9779 receives commands from the body controller and drives relays or solenoids. The integrated protection features, such as over-temperature and over-current limiting, enhance system robustness. The SPI variant (L9779WD-SPI) allows for real-time diagnostics and configuration, which is valuable in modern vehicles with advanced fault reporting. Compared to discrete relay drivers, the L9779 offers a compact, reliable solution with built-in diagnostics.
Recommended
Start-Stop Systems
In start-stop systems, the L9779 manages the starter relay and injector drivers during engine restart. The starter relay drivers (OUT13, OUT14) provide high-current drive for the starter motor relay, while the injector drivers ensure precise fuel delivery for quick restart. The power latch mode allows the system to maintain power during the stop phase and quickly re-engage on restart. The L9779's BCD6S technology ensures efficient operation with minimal quiescent current, which is critical for battery conservation in start-stop systems. The device's diagnostic features help detect faults in the starter or injector circuits, improving system reliability. Compared to using separate drivers, the L9779 reduces complexity and ensures synchronized operation between the starter and injectors.
Recommended
Motorcycle Engine Control
The L9779 is suitable for motorcycle engine control units, where space is limited and reliability is critical. Its four injector drivers can handle single or dual-cylinder configurations, and the two starter relay drivers manage the starter motor. The compact 64-pin HiQUAD package fits well in the constrained PCB space of motorcycle ECUs. The device's wide operating voltage range accommodates the varying battery voltages in motorcycles. The power latch mode provides a simple key-switch interface, reducing external components. Compared to automotive ECUs, motorcycle applications may require fewer injector drivers, but the L9779's flexibility allows unused channels to be disabled. The BCD6S technology ensures reliable operation in the vibration and temperature extremes of motorcycle environments.
Recommended
Small Engine Management (Generators, Marine)
For small engines in generators or marine applications, the L9779 provides a robust solution for fuel injection and starter control. Its four injector drivers can be used for single or multi-cylinder small engines, and the starter relay drivers handle the starting system. The device's automotive-grade design ensures reliability in harsh environments, including high humidity and temperature variations. In a generator application, the L9779 works with an ECU to manage fuel delivery and starting, improving efficiency and reducing emissions. The power latch mode allows for simple key-switch or remote-start control. Compared to larger automotive ECUs, the L9779 offers a cost-effective, integrated solution for small engines. The SPI variant enables remote diagnostics, which is valuable for stationary or marine installations.
Recommended
Recommended Products Summary
Engineering reference data for L9779 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | L9779WD | L9779WD-SPI |
|---|---|---|---|
| Package | 64-HiQUAD | 64-HiQUAD - same | 64-HiQUAD - same |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics |
| SPI Interface | No | No | Yes |
| Injector Drivers | 4 (OUT1-4) | 4 (OUT1-4) | 4 (OUT1-4) |
| Starter Relay Drivers | 2 (OUT13, OUT14) | 2 (OUT13, OUT14) | 2 (OUT13, OUT14) |
| Power Latch Mode | Yes | Yes | Yes |
| Technology | BCD6S | BCD6S | BCD6S |
| Automotive Grade | Yes | Yes | Yes |
Key Differentiators
- Integrated multifunction design (vs Discrete driver solutions)
- BCD6S technology (vs Older BCD processes)
- Automotive-grade reliability (vs Commercial-grade PMICs)
Design Notes
The L9779 in a 64-pin HiQUAD package can dissipate significant power when driving multiple injectors. Ensure adequate PCB copper area and thermal vias under the package to keep the junction temperature within limits. For continuous operation at high ambient temperatures (e.g., 125°C), consider a thermal analysis to verify the heat sink requirements.
Place decoupling capacitors close to the VCC and GND pins to minimize voltage spikes during injector switching. Use a low-ESR ceramic capacitor (e.g., 100nF) for high-frequency noise and a larger electrolytic capacitor (e.g., 10uF) for bulk energy storage. Route high-current output traces with adequate width to handle the injector current without excessive voltage drop.
In no power latch/no SEO mode, the key-switch has direct shut-off access to the injector stages (OUT1-4) and starter relay drivers (OUT13, OUT14). Ensure the key-switch circuit is designed to handle the injector current and provide a clean shut-off to avoid inductive spikes. Also, verify the SPI interface (if used) is properly configured with correct pull-up resistors and timing to prevent communication errors.
Compliance Information
RoHS compliant per STMicroelectronics product page. AEC-Q100 qualification not specified; designed for automotive environment but not explicitly stated as AEC-Q100 qualified.
