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STMicroelectronics L9409F
- Part No.:
- L9409F
- Manufacturer:
- STMicroelectronics
- Category:
- Special Purpose Regulators
- Package:
- Multiwatt-8 (Straight Leads)
- Datasheet:
-
L9409F.pdf
- Description:
- IC DVR HI SIDE MULTI MULTIWATT8
- Quantity:
- Payment:
- Shipping:
Inventory:4,232
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Product details
Overview
L9409F from STMicroelectronics is an automotive alternator voltage regulator IC with integrated high-side field driver (130 mΩ), Load Response Control (LRC), dual battery voltage sensing (B and S pins), and thermal shutdown at 175 °C. It regulates 12 V alternators using fixed-frequency PWM, supports self-start via phase frequency detection, and complies with VW "Z"-shaped regulation curve requirements for engine stability under load transients.
For engineers reviewing the L9409F datasheet, L9409F pinout, L9409F application, or L9409F equivalent, this device is selected for automotive generator control where fail-safe battery sensing, LRC-enabled low-speed torque smoothing, lamp/relay driver integration, and -40 to 150 °C junction operation are required.
Technical Context
The L9409F implements analog or digital fixed-frequency PWM regulation of the alternator field winding, with set-point voltage thermally compensated across case temperature (-40 to 150 °C) and a programmable "Z"-shaped curve per VW specification. Regulation uses either B-pin (generator output) or S-pin (direct battery sense) feedback, with automatic fallback to B if S is open.
LRC activates after a 2.1–3.5 s delay when alternator speed exceeds 130–160 Hz, ramping field duty cycle over 2.1–2.9 s to suppress engine vibration during low-speed electrical load insertion. Field, lamp (L), and relay (R) drivers include short-circuit protection and diagnostic monitoring with fault indication delay (0.8–1.2 s).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Regulation Set-Point @ 25 °C | 14.5 V nominal - defines target battery voltage under standard conditions |
| Field Driver RON | 130 mΩ max at 125 °C - enables high-efficiency field current control with low conduction loss |
| LRC Enable Frequency | 130–160 Hz - triggers load response only below ~310 Hz (idle/low-RPM alternator operation) |
| Thermal Shutdown | 175 ±15 °C - protects against destructive overheating during overload or poor heatsinking |
| Standby Current | ≤400 µA at 13 V - minimizes parasitic drain on vehicle battery when engine is off |
| Load Regulation Error | ≤200 mV from 10% to 90% load - ensures stable output voltage despite large current swings |
| Sense Pin Voltage Range | 8–16 V operating - supports direct connection to 12 V battery terminal with robust noise immunity |
Pinout & Package
Package: Multiwatt8 (vertical, through-hole), ECOPACK® compliant, thermal resistance junction-to-case = 1.5 °C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - P | Phase input | Detects alternator phase voltage to initiate field regulation and enable LRC timing |
| 2 - FM | Field monitor output | Open-collector signal indicating active field drive state for diagnostics |
| 3 - R | Relay high-side driver | Drives relay coil up to 2.5 A with 300 µs activation delay and 0.2–0.6 V saturation |
| 4 - L | Lamp low-side driver | Sinks warning lamp current (≤2.5 A); senses key switch via wake-up threshold (0.8–1.1 V) |
| 5 - G | Power ground | Main return path for field, lamp, and relay drivers; referenced for all internal sensing |
| 6 - S | Battery sense input | Direct connection to battery + for accurate regulation; fallback to B pin if open |
| 7 - F+ | Field high-side driver output | Switches alternator field winding with 130 mΩ RON; includes short-circuit protection |
| 8 - B | Voltage supply & generator sense | Primary power input (8–28 V) and secondary regulation feedback path when S is disconnected |
Key Features
| Feature | Design Value |
|---|---|
| Z-shaped regulation curve | Complies with VW specification to maintain engine stability during HVAC or lighting load steps at idle |
| Fail-safe dual voltage sensing | Automatic switchover from S-pin to B-pin sensing if battery sense line opens - prevents overvoltage |
| Self-start via residual magnetism | Initiates field excitation without external key signal if L-pin connection is lost - ensures restart capability |
| Integrated lamp & relay drivers | Eliminates need for external discrete drivers; provides diagnostic signaling and ignition-coil interface |
| Complex diagnostics with delay | Filters transient faults with 0.8–1.2 s confirmation window to prevent false warning lamp activation |
Applications
| Passenger Vehicle Alternator Control | Commercial Truck Generator Management |
|---|---|
|
Use Scenario: 12 V alternator in gasoline-powered sedan regulating battery charge while powering HVAC, infotainment, and lighting loads. IC Role / Device Role / Timing Role: Primary voltage regulator with LRC activation below 310 Hz to suppress engine shudder during AC compressor engagement at idle. Use Value: Prevents driver-perceived vibration by ramping field current over 2.1–2.9 s instead of abrupt step change. |
Use Scenario: Heavy-duty diesel truck alternator supplying high-current loads (air compressors, trailer lighting) under wide ambient temperature range. IC Role / Device Role / Timing Role: Dual-sense regulator (S-pin for precision, B-pin fallback) ensuring ≤200 mV load regulation error across 10–90% load swing. Use Value: Maintains stable 14.5 V battery voltage despite 100+ A load transients, reducing deep-cycle battery stress. |
| Automotive Aftermarket Replacement Module | Engine Test Bench Power System |
|
Use Scenario: Drop-in replacement regulator for legacy Bosch or Denso alternators in repair workshops. IC Role / Device Role / Timing Role: Direct-fit Multiwatt8 package with pin-compatible field/lamp/relay interfaces and VW-compliant Z-curve regulation. Use Value: Enables OEM-equivalent performance without rewiring; supports key recognition and pre-excitation for reliable cold starts. |
Use Scenario: Controlled alternator testing on dynamometer rigs simulating real-world load profiles and thermal stress. IC Role / Device Role / Timing Role: Regulator with thermal shutdown (175 °C), diagnostic FM output, and traceable field current control for validation reporting. Use Value: Provides repeatable, instrumented field drive behavior and fault logging for ISO 16750-2 compliance testing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar alternator voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| L9409TR | Same die, but in tape-and-reel packaging (vs. tube); identical electrical specs and pinout | No functional difference - selected for automated SMT assembly vs. manual through-hole insertion | Choose L9409TR for high-volume PCB assembly; L9409F remains optimal for prototyping and service replacement |
| L9409D | Includes enhanced ESD protection (±4 kV HBM vs. ±2 kV) and extended transient immunity (60 V pulse 3 vs. 40 V load dump) | Required for vehicles with aggressive ISO 7637-3 pulse 3 environments (e.g., premium EV platforms with regenerative braking spikes) | Select L9409D where system-level EMC validation requires higher transient robustness; L9409F suffices for standard ICE platforms |
Compared with L9409TR and L9409D, the L9409F offers identical regulation performance and diagnostics in a tube-packaged Multiwatt8 format optimized for serviceability and manual integration, while trading off ESD/transient headroom for cost-sensitive 12 V ICE applications.
Availability
L9409F is available at Aetrix Electronics and suitable for passenger vehicle alternator control, commercial truck generator management, and automotive aftermarket replacement modules requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for L9409F includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power ICs, sensors, and automotive-grade analog devices since 1987.
The L9409F belongs to ST's automotive power management product line, engineered specifically for intelligent alternator regulation in 12 V ICE vehicles-emphasizing fail-safe operation, engine vibration suppression, and diagnostic transparency.
FAQ
What is the purpose of the S pin versus the B pin in the L9409F?
The S pin provides direct battery voltage sensing for precise regulation, requiring a dedicated wire to the battery positive terminal. If the S connection opens, the L9409F automatically switches regulation to the B pin (generator output), maintaining safe operation without overvoltage. This dual-sense architecture delivers fail-safe redundancy critical for automotive reliability.
How does Load Response Control (LRC) reduce engine vibration?
LRC activates only below 160 Hz (idle/low-RPM alternator speed) and delays field current ramp-up by 2.1–3.5 s before gradually increasing duty cycle over 2.1–2.9 s. This controlled torque rise prevents sudden alternator drag on the engine crankshaft during HVAC or headlight load steps, eliminating perceptible shudder at idle.
Can the L9409F operate without connection to the L (lamp) pin?
Yes-the L pin serves dual roles: driving the dashboard warning lamp and detecting ignition switch status. If L is unconnected, the L9409F initiates field excitation using residual magnetism in the alternator rotor, enabling self-start. Lamp functionality is lost, but regulation and LRC remain fully operational.
What thermal protection mechanisms does the L9409F implement?
The L9409F features thermal shutdown at 175 ±15 °C, verified across its full -40 to 150 °C junction range. It also includes thermal compensation of the regulation set-point (e.g., -10 mV/°C between -10 and 100 °C), preventing overcharging at high temperatures. The Multiwatt8 package's 1.5 °C/W junction-to-case resistance supports effective heatsinking in automotive mounting configurations.
L9409F Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- Multiwatt-8 (Straight Leads)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Applications:
- -
- Voltage - Input:
- -
- Number of Outputs:
- -
- Voltage - Output:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- Multiwatt-8 (Straight Leads)
L9409F FAQ
1.How can I place an order for L9409F through Aetrix?
Please submit a Request for Quotation (RFQ) for L9409F on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for L9409F reliable?
The price and inventory of L9409F are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L9409F is usually 5 days.
3.What payment methods are accepted for L9409F?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L9409F transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L9409F?
L9409F orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L9409F order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for L9409F?
For technical support, including L9409F datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L9409F requirements.
6.How does Aetrix verify that L9409F is sourced from the original manufacturer or authorized distributors?
All L9409F products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that L9409F meets industry standards.
7.What is the process for return or replacement of L9409F?
All L9409F units undergo pre-shipment inspection (PSI). If there is an issue with L9409F, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The L9409F part is unused and in its original packaging.
Return procedure for L9409F:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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