STMicroelectronics L9915-CB

Overview

L9915-CB from STMicroelectronics is a monolithic C-terminal alternator voltage regulator (CTAVR) for automotive 12 V/24 V systems. It implements closed-loop regulation of generator output via PWM-controlled high-side field driver (f_FSW = 212.5–287.5 Hz), supports ECU-driven external regulation (C-terminal protocol, 100–500 Hz), provides thermally compensated internal reference (VBISP = 14.37–14.73 V @ 30 °C), and integrates lamp driver, self-start, load response control (LRC), and field monitor (FM) output.

For engineers reviewing the L9915-CB datasheet, L9915-CB pinout, L9915-CB application, or L9915-CB equivalent, this device is selected for engine control integration, battery voltage stability under dynamic load, fault-aware warning lamp signaling, and thermal-safe field current management in modern alternator control units.

Technical Context

The L9915-CB operates in three primary modes: pre-excitation (fixed F duty cycle DFPreex = 11–14 %), internal regulation (temperature-compensated VBISP with ±3.5 mV/°C drift), and external regulation (C-terminal PWM duty cycle mapping to set-point: 10 % → 11.5–11.9 V, 73 % → 14.37–14.73 V, 90 % → 15.1–15.5 V). It transitions between modes using PH pin frequency thresholds: fPHPrex = 102–138 Hz (exit pre-excitation), fPSS = 255–345 Hz (self-start activation), and fPLRC = 272–368 Hz (LRC entry/exit).

Its protection architecture includes field short-circuit detection (IFOVP = 8.5–15 A), thermal shutdown (Tj-sd = 160–190 °C), cranking security (VBLOW = 6–7 V freeze, VBUV = −400 mV recovery), and phase regulation (VPprTh = 6.7–8.7 V). The FM pin delivers synchronized 212.5–287.5 Hz PWM with 5–95 % duty cycle for real-time field current monitoring by the ECU.

Key Specifications

Pinout & Package

Package: Multiwatt8 (vertical mount, 8-pin SIP, JEDEC MS-012AC), thermal resistance R_{th_j-case} = 1.5 °C/W, operating junction temperature range T_j = −40 to +150 °C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLE6820-2G and MC33VR5000, the L9915-CB offers simpler C-terminal PWM integration, autonomous self-start behavior, and lower standby current (≤350 μA), making it optimal for cost-sensitive, ECU-light, or legacy protocol-based alternator control designs.

Availability

L9915-CB is available at Aetrix Electronics and suitable for automotive powertrain control, battery management systems, and 12 V/24 V alternator assemblies requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for L9915-CB 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 specializing in automotive, industrial, and power management ICs, with broad portfolio coverage and AEC-Q100 qualified products.

The L9915-CB belongs to ST's automotive alternator regulator product line, designed specifically for robust, protocol-flexible, and thermally resilient voltage control in engine-driven generators.

FAQ

What is the purpose of the "XX" pin on the L9915-CB?

Pin 2 ("XX") is a reserved pin with no internal electrical function and must be connected to GND per the datasheet. It serves mechanical stabilization and thermal conduction roles in the Multiwatt8 package but does not participate in regulation, communication, or protection logic.

How does the L9915-CB handle battery voltage collapse during engine cranking?

During cranking, the L9915-CB monitors pin B voltage and enters "frozen" mode when VB drops below VBLOW (6–7 V). In this state, F and FM outputs disable, but L remains active to illuminate the warning lamp. Regulation resumes only after VB rises above VBUV (−400 mV), preventing erratic behavior during transient low-voltage events.

Can the L9915-CB operate without an ECU connection on the C pin?

Yes-the L9915-CB defaults to internal regulation mode using its thermally compensated reference (VBISP = 14.37–14.73 V @ 30 °C) when the C pin is floating or disconnected. Self-start functionality further ensures regulation initiates autonomously once PH frequency exceeds fPSS = 255–345 Hz.

What is the functional difference between DFPreex and DFSS duty cycles?

DFPreex (11–14 %) applies during pre-excitation-activated by key-on or C-terminal activity before alternator rotation. DFSS (4–8 %) applies during self-start-triggered solely by PH frequency exceeding fPSS, with no C-terminal or L-pin stimulus. Both initiate field current but serve distinct system states: controlled readiness vs. autonomous cut-in.