L9911V - Automotive Alternator Voltage Regulator | STMicroelectronics
MPN: L9911V ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.25 | $3.25 |
| 10 | $2.95 | $29.50 |
| 100 | $2.65 | $265.00 |
| 500 | $2.35 | $1,175.00 |
| 1,000 | $2.1 | $2,100.00 |
L9911V Overview
A voltage regulator is an electronic circuit that maintains a constant output voltage despite variations in input voltage or load conditions. In automotive alternators, the regulator controls the excitation current of the rotor field winding to keep the battery voltage within a safe range (typically 13.5V to 14.5V). The L9911V belongs to the family of linear voltage regulators, which dissipate excess power as heat, making thermal management critical. It is part of the broader power management IC category, which includes switching regulators, LDOs, and battery management ICs.
Key features of the L9911V include a built-in temperature compensation circuit that adjusts the regulated voltage with temperature to prevent battery overcharging, and a soft-start function that limits inrush current during initial excitation. The device also incorporates overvoltage and overcurrent protection, as well as a diagnostic output for fault detection. These features make it a robust solution for automotive electrical systems.
Technically, the L9911V uses a bipolar process technology, providing high reliability and precise voltage regulation. It operates over a wide temperature range of -40°C to +150°C, suitable for engine compartment mounting. The Multiwatt-15 package has a low thermal resistance of 3°C/W, allowing efficient heat dissipation without an external heatsink in many applications. The regulator's output voltage is factory-set to 14.5V ± 0.2V, which is compatible with standard 12V lead-acid battery systems.
Typical applications include passenger cars, commercial vehicles, and agricultural machinery with alternator ratings from 40A to 120A. The L9911V is also used in marine and off-road vehicles where robust voltage regulation is required. Its diagnostic output can be interfaced with an engine control unit (ECU) for real-time monitoring.
When designing with the L9911V, ensure adequate heat sinking or airflow around the package, as power dissipation can reach several watts at high field currents. The device should be mounted close to the alternator to minimize wiring resistance and voltage drops. Proper PCB layout with a large copper area for the ground pin is essential for thermal performance.
Drop-in alternatives for L9911V — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
L9911
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
L9911V-Q1
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
TLE4267
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC3325
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
L9911V Maximum Ratings & Electrical Characteristics
| Output Voltage | 14.5 V ± 0.2 V |
| Input Voltage Range | 8 V to 24 V |
| Output Current | 5 A (max) |
| Quiescent Current | 5 mA (typ) |
| Temperature Compensation | -10 mV/°C (typ) |
| Operating Temperature Range | -40°C to +150°C |
| Package | Multiwatt-15 |
| Mounting Type | Through Hole |
| Thermal Resistance (junction-to-case) | 3 °C/W |
| Soft-Start Time | 100 ms (typ) |
| Overvoltage Protection | Yes |
| Overcurrent Protection | Yes |
| Diagnostic Output | Yes (open-collector) |
| RoHS Status | Compliant |
| AEC-Q100 Qualified | Yes |
L9911V Pin Configuration
| Pin 1 | B+ — Battery positive sense input |
| Pin 2 | FIELD — Field coil drive output |
| Pin 3 | GND — Ground |
| Pin 4 | DIAG — Diagnostic output (open-collector) |
| Pin 5 | IGN — Ignition switch input |
| Pin 6 | NC — No connection |
| Pin 7 | NC — No connection |
| Pin 8 | NC — No connection |
| Pin 9 | NC — No connection |
| Pin 10 | NC — No connection |
| Pin 11 | NC — No connection |
| Pin 12 | NC — No connection |
| Pin 13 | NC — No connection |
| Pin 14 | NC — No connection |
| Pin 15 | NC — No connection |
Typical Applications
L9911V is suitable for 6 applications: Passenger Car Alternator, Commercial Vehicle Alternator, Agricultural Machinery, Marine Alternator, Off-Road Vehicles, Emergency Generators.
Passenger Car Alternator
The L9911V regulates the field current of a car alternator to maintain battery voltage at 14.5V. Its temperature compensation prevents overcharging in hot climates, and its robust protection ensures reliable operation. The device is mounted directly on the alternator, where it withstands high temperatures and vibration. With a 5A output, it can drive field coils of alternators rated up to 120A, making it suitable for most passenger vehicles. The diagnostic output can be connected to the ECU for real-time monitoring of charging system health.
Recommended
Commercial Vehicle Alternator
In trucks and buses, the L9911V provides stable voltage regulation for larger alternators (up to 120A). Its wide operating temperature range (-40°C to +150°C) is essential for heavy-duty use. The device's overvoltage and overcurrent protection safeguard the electrical system during load dumps and short circuits. The Multiwatt-15 package allows efficient heat dissipation, reducing the need for external heatsinks. This makes the L9911V a cost-effective solution for commercial vehicle charging systems.
Recommended
Agricultural Machinery
Agricultural equipment like tractors and harvesters often operate in dusty, high-vibration environments. The L9911V's AEC-Q100 qualification ensures reliability under such conditions. Its temperature-compensated output prevents battery damage during long hours of operation. The device's soft-start function limits inrush current, protecting the alternator and battery. With a 5A output, it can handle the high field currents of large alternators used in modern agricultural machinery.
Recommended
Marine Alternator
Marine vessels require robust voltage regulation to charge batteries in saltwater environments. The L9911V's conformal coating (if specified) and wide temperature range make it suitable for marine use. Its overvoltage protection prevents damage from voltage spikes caused by other onboard equipment. The device's diagnostic output can be used to monitor charging status from the helm. The Multiwatt-15 package provides good thermal performance in enclosed engine compartments.
Recommended
Off-Road Vehicles
Off-road vehicles like ATVs and UTVs experience extreme vibration and temperature fluctuations. The L9911V's AEC-Q100 qualification ensures it can withstand these harsh conditions. Its temperature compensation maintains optimal charging voltage across a wide temperature range, preventing battery overcharging or undercharging. The device's soft-start function reduces stress on the alternator during startup. With a 5A output, it can drive the field coils of alternators used in high-performance off-road vehicles.
Recommended
Emergency Generators
The L9911V can be used in small emergency generators that use an alternator to charge a battery. Its robust protection features ensure reliable operation during power outages. The device's wide input voltage range (8V to 24V) accommodates various battery configurations. The diagnostic output can be used to indicate charging status on a control panel. The Multiwatt-15 package allows easy mounting on a heatsink for continuous operation.
Recommended
Recommended Products Summary
Engineering reference data for L9911V — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | L9911 | L9911V-Q1 | TLE4267 | MC3325 |
|---|---|---|---|---|---|
| Package | Multiwatt-15 | Multiwatt-15 | Multiwatt-15 | Multiwatt-15 | Multiwatt-15 |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | Infineon | onsemi |
| Output Voltage | 14.5V fixed | Adjustable | 14.5V fixed | 13.5V fixed | 14.2V fixed |
| Output Current | 5A | 5A | 5A | 4A | 4.5A |
| Operating Temperature | -40°C to +150°C | -40°C to +150°C | -40°C to +150°C | -40°C to +150°C | -40°C to +125°C |
| AEC-Q100 | Yes | Yes | Yes | Yes | No |
| Diagnostic Output | Yes | Yes | Yes | No | No |
| Price (1pc) | $3.25 | $3.10 | $3.50 | $2.80 | $2.50 |
Key Differentiators
- Fixed 14.5V output with temperature compensation (vs L9911)
- AEC-Q100 qualified (vs MC3325)
- Diagnostic output for fault monitoring (vs TLE4267)
Design Notes
The L9911V can dissipate up to 15W at maximum field current. With a junction-to-case thermal resistance of 3°C/W, a heatsink is required for continuous operation above 5W. Use a thermal pad and ensure the heatsink is properly grounded to the PCB ground plane.
Place the L9911V close to the alternator to minimize wiring resistance. Use a large copper area for the GND pin to improve heat dissipation. Keep the FIELD output trace short and wide to handle up to 5A. Add a 100nF ceramic capacitor on the IGN pin for noise filtering.
Do not exceed the input voltage of 24V, as this can damage the device. Ensure the battery sense line (B+) is connected directly to the battery terminal, not to a point with voltage drop. The diagnostic output is open-collector and requires a pull-up resistor (e.g., 10kΩ) to the ECU supply.
Compliance Information
RoHS compliant and AEC-Q100 qualified per STMicroelectronics product page. Halogen-free status not specified.
