L9915-TR - Automotive Alternator Voltage Regulator | STMicroelectronics
MPN: L9915-TR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.5 | $2.50 |
| 10 | $2.25 | $22.50 |
| 100 | $2 | $200.00 |
| 500 | $1.8 | $900.00 |
| 1,000 | $1.6 | $1,600.00 |
L9915-TR 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 field current of the rotor to keep the output voltage within a specified range, typically around 14V for a 12V system. The L9915-TR integrates the sensing, control, and drive functions into a single IC, replacing discrete components and improving reliability. This device is part of the broader power management IC category, which includes linear regulators, switching regulators, and battery management ICs.
Key features of the L9915-TR include its ability to handle high operating temperatures up to 150°C, making it suitable for under-hood automotive environments. It offers a regulated output voltage of 14.5V with a tolerance of ±1%, ensuring consistent charging performance. The device also includes built-in protection features such as over-temperature shutdown and over-voltage protection, safeguarding the alternator and battery from damage. Its low quiescent current consumption helps reduce parasitic drain on the battery when the engine is off.
From a technical perspective, the L9915-TR employs a bipolar technology that provides robust performance in harsh automotive conditions. The device operates by comparing the battery voltage to an internal reference and adjusting the field current accordingly. This closed-loop control ensures rapid response to load transients, maintaining voltage stability. The package is designed for efficient heat dissipation, with a thermal resistance of 50°C/W, allowing the regulator to dissipate power without excessive junction temperature rise.
Typical applications include passenger cars, commercial vehicles, and agricultural machinery that use alternators for battery charging. The L9915-TR is also used in marine and off-road vehicles where reliable charging is critical. Its robust design and automotive-grade qualification make it a preferred choice for OEM and aftermarket alternator manufacturers.
When designing with the L9915-TR, it is essential to ensure proper heat sinking and PCB layout to manage thermal dissipation. The device should be placed close to the alternator's field winding to minimize parasitic inductance. Additionally, the sense line should be connected directly to the battery positive terminal to avoid voltage drops in the wiring, ensuring accurate regulation.
Drop-in alternatives for L9915-TR — 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 L9915-TR (same form factor and footprint) — differing in Input Voltage Range, Mounting Type, Output Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
L9915
✅ Drop-In✓ In Stock
$4.19 / Unit
View Datasheet →L9915A
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
L9915B
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
TLE4267
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
NCV4275
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
L9915-TR Maximum Ratings & Electrical Characteristics
| Output Voltage | 14.5 V |
| Output Voltage Tolerance | ±1% |
| Operating Temperature Range | -40°C to +150°C |
| Input Voltage Range | 8 V to 24 V |
| Quiescent Current | 5 mA |
| Maximum Field Current | 5 A |
| Package Type | SO-8 |
| Mounting Type | Surface Mount |
| Thermal Resistance (θJA) | 50 °C/W |
| Over-Temperature Shutdown | Yes |
| Over-Voltage Protection | Yes |
| RoHS Compliant | Yes |
| AEC-Q100 Qualified | Yes |
| Regulation Type | Linear |
| Number of Outputs | 1 |
L9915-TR Pin Configuration
| Pin 1 | B+ — Battery positive sense input |
| Pin 2 | GND — Ground |
| Pin 3 | FIELD — Field driver output |
| Pin 4 | IGN — Ignition switch input |
| Pin 5 | LAMP — Charge indicator lamp output |
| Pin 6 | SENSE — Voltage sense input |
| Pin 7 | NC — No connect |
| Pin 8 | B+ — Battery positive sense input |
Typical Applications
L9915-TR is suitable for 6 applications: Automotive Alternator Voltage Regulation, Commercial Vehicle Charging Systems, Marine Alternator Systems, Agricultural Machinery, Off-Road Vehicles, Emergency Generators.
Automotive Alternator Voltage Regulation
The L9915-TR is specifically designed for automotive alternator voltage regulation. It maintains the battery voltage at 14.5V ±1% across varying engine speeds and electrical loads. The device senses the battery voltage and adjusts the rotor field current to keep the output stable. Its wide operating temperature range (-40°C to +150°C) and AEC-Q100 qualification make it ideal for under-hood environments. The low quiescent current (5 mA) minimizes battery drain when the engine is off, and the over-temperature and over-voltage protections ensure reliable operation in harsh conditions.
Recommended
Commercial Vehicle Charging Systems
In commercial vehicles such as trucks and buses, the L9915-TR ensures reliable battery charging. The device's ability to handle up to 5A field current makes it suitable for larger alternators used in these vehicles. The robust design withstands the vibrations and temperature extremes typical of commercial vehicle operation. The regulator's precise voltage control prevents overcharging, extending battery life and reducing maintenance costs. The SO-8 package allows for compact integration into the alternator's control module.
Recommended
Marine Alternator Systems
Marine environments present unique challenges, including saltwater corrosion and high humidity. The L9915-TR's conformal coating and robust packaging provide protection against these conditions. The wide input voltage range (8V to 24V) accommodates voltage fluctuations common in marine electrical systems. The device's over-temperature shutdown prevents damage during prolonged high-load operation. Its AEC-Q100 qualification ensures reliability in the demanding marine environment.
Recommended
Agricultural Machinery
Agricultural machinery such as tractors and harvesters operate in dusty, high-vibration environments. The L9915-TR's rugged design and wide temperature range make it suitable for these conditions. The regulator ensures consistent battery charging, which is critical for starting and operating heavy equipment. The low quiescent current helps preserve battery charge during long periods of inactivity. The device's protection features prevent damage from voltage spikes and overheating.
Recommended
Off-Road Vehicles
Off-road vehicles, including ATVs and utility vehicles, require reliable charging systems. The L9915-TR's ability to operate at high temperatures and handle high field currents makes it ideal for these applications. The device's compact SO-8 package fits into space-constrained alternator housings. The precise voltage regulation ensures optimal battery charging, even under heavy electrical loads from winches and lights. The over-voltage protection safeguards the electrical system from damage.
Recommended
Emergency Generators
Emergency generators used in backup power systems rely on alternators for battery charging. The L9915-TR provides stable voltage regulation, ensuring the generator's battery is always ready. The device's wide operating temperature range allows it to function in various environmental conditions. The low quiescent current is beneficial for maintaining battery charge during standby. The regulator's protection features enhance the reliability of the generator's starting system.
Recommended
Recommended Products Summary
Engineering reference data for L9915-TR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | L9915 | L9915A | L9915B | TLE4267 | NCV4275 |
|---|---|---|---|---|---|---|
| Package | SO-8 | SO-8 | SO-8 | SO-8 | SO-8 | SO-8 |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics | Infineon | onsemi |
| Output Voltage | 14.5 V | 14.5 V | 14.5 V | 14.5 V | 13.5 V | 14.0 V |
| Output Voltage Tolerance | ±1% | ±1% | ±1% | ±1% | ±2% | ±2% |
| Operating Temperature Range | -40°C to +150°C | -40°C to +150°C | -40°C to +150°C | -40°C to +150°C | -40°C to +150°C | -40°C to +150°C |
| Quiescent Current | 5 mA | 5 mA | 5 mA | 5 mA | 6 mA | 4 mA |
| Maximum Field Current | 5 A | 5 A | 5 A | 5 A | 4 A | 4 A |
| AEC-Q100 Qualified | Yes | Yes | Yes | Yes | Yes | Yes |
Key Differentiators
- Higher output voltage accuracy (vs TLE4267)
- Higher field current capability (vs NCV4275)
- Same-brand drop-in compatibility (vs L9915)
Design Notes
The L9915-TR has a thermal resistance of 50°C/W. In an alternator application, the regulator may dissipate up to 2W, resulting in a temperature rise of 100°C above ambient. Ensure adequate PCB copper area and airflow to keep the junction temperature below 150°C. A thermal pad on the PCB can improve heat dissipation.
Place the L9915-TR close to the alternator's field winding to minimize parasitic inductance. Use a 100nF ceramic capacitor on the B+ pin and a 10µF electrolytic capacitor on the output to filter noise. The sense line should be routed directly to the battery positive terminal to avoid voltage drops.
Do not exceed the maximum input voltage of 24V. Ensure the ignition input (IGN) is properly protected against load dump transients. The LAMP output should be connected to a suitable indicator lamp with a current-limiting resistor. Avoid connecting the sense line to the alternator output instead of the battery, as this can cause inaccurate regulation.
Compliance Information
RoHS compliant and AEC-Q100 qualified per STMicroelectronics datasheet. Halogen-free status not specified.
