STMicroelectronics L9473J

Overview

L9473J from STMicroelectronics is a monolithic automotive alternator voltage regulator IC with high-side field driver, thermistor-compensated set-point control, thermal shutdown at 175°C ±15°C, 9.0 A field limit current at 25°C, and integrated lamp/relay/phase/DF monitoring - deployed in 12 V/24 V vehicle charging systems to maintain stable battery voltage under variable load and temperature.

For engineers reviewing the L9473J datasheet, L9473J pinout, L9473J application, or L9473J equivalent, this page delivers verified electrical specs (e.g., 340–460 Hz PWM frequency, 14.41–15.3 V set-point range), package mapping to Multiwatt8, thermal protection behavior, and real-world fault-handling logic for generator regulation design validation.

Technical Context

The L9473J implements closed-loop voltage regulation via variable-frequency PWM control of the alternator's field winding, using phase-sense (P) and field-monitor (DF) feedback to initiate and terminate regulation phases based on rotor speed thresholds (FP-IR = 123–167 Hz, FP-TR = 59–86 Hz). It integrates autostart logic that activates only when VP exceeds 1.1 V and FP exceeds 123 Hz.

Thermal compensation uses either an external NTC thermistor (10 kΩ @ 25°C) connected between VGO and TS or a default curve activated when TS is open; set-point voltage varies from 13.4 V to 15.3 V across -40°C to +120°C junction temperature, with load regulation held to ≤300 mV and speed regulation to ≤100 mV.

Key Specifications

Pinout & Package

The L9473J is housed in a Multiwatt8 package with exposed metal tab (Pin 5) thermally connected to the die substrate for direct heatsink mounting. Pin 5 must not be used as signal ground; ASVR ground is exclusively Pin 3.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar automotive alternator regulation applications.

Compared with LM34907T and UC3906N, the L9473J delivers full-system integration - combining field drive, thermal compensation, phase sensing, and multi-output diagnostics in one Multiwatt8 package - reducing external component count by ≥7 parts and enabling faster fault response (<1.3 s).

Availability

L9473J is available at Aetrix Electronics and suitable for automotive battery charging systems, engine control unit interfaces, thermally compensated alternators, and relay-driven auxiliary load control requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for L9473J 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 L9473J belongs to ST's Automotive Power Management product line, engineered specifically for intelligent alternator regulation in ICE and mild-hybrid vehicles - emphasizing thermal robustness, fault resilience, and seamless integration with engine control architectures.

FAQ

What is the function of the TS pin on the L9473J?

The TS pin accepts an external NTC thermistor (10 kΩ @ 25°C) to provide ambient temperature compensation for the voltage set-point. When left unconnected, the device defaults to a factory-defined compensation curve. The TS pin does not source or sink significant current and must be biased only via the thermistor between VGO and TS.

How does the L9473J handle thermal overload?

The L9473J incorporates a thermal shutdown circuit that disables the field driver when junction temperature reaches 175°C ±15°C. Recovery occurs automatically once temperature drops below hysteresis threshold (~160°C). The Multiwatt8 package's low R_{th j-case} (1.5°C/W) enables effective heatsinking through the exposed metal tab (Pin 5).

Can the L9473J operate without a battery connected?

Yes - the L9473J supports no-battery operation with generator output voltage maintained between VSP −2 V and VSP +2 V at 2 A load. However, lamp diagnostics and autostart sequencing require minimum VGO voltage (≥10.95 V) and phase signal presence to initiate regulation.

What is the purpose of the P (Phase) pin?

The P pin detects AC voltage from the alternator's stator phase winding to determine rotor speed. Regulation begins only when phase frequency exceeds FP-IR (123–167 Hz) and voltage exceeds VP-IR (1.1–1.5 V), ensuring stable operation after engine start and preventing premature field activation during cranking.