STMicroelectronics L9678P

Overview

L9678P from STMicroelectronics is an AEC-Q100 qualified automotive user-configurable airbag and battery cut-off IC. It integrates energy reserve boost regulation (23 V or 33 V ±5%), dual linear supplies (5.0 V/7.2 V ±4%), a fully integrated 3.3 V ±4% regulator, squib/pyroswitch deployment drivers (4-channel HSD/LSD), PSI-5 remote sensor interface, ISO9141 transceiver, and safing logic - deployed in low-end airbag control units for occupant restraint activation.

For engineers reviewing the L9678P datasheet, L9678P pinout, L9678P application, or L9678P equivalent, this device supports critical safety-critical power sequencing, multi-level squib diagnostics (Rmeasure, STB, STG, leakage), configurable safing logic, and system voltage monitoring via integrated ADC - essential for functional safety compliance in ASIL-B airbag systems.

Technical Context

The L9678P implements a hierarchical power architecture: high-frequency (1.882 MHz) ERBOOST switching regulator feeds energy reserve capacitors, while three independent linear regulators (VDD5, VDD3V3, VSF) supply subsystems with ±4% accuracy. Its deployment drivers support programmable current profiles (1.2 A @ 2 ms, 1.75 A @ 0.5/0.7 ms) and integrated safing FET regulation (20 V/25 V nominal).

System intelligence includes dual oscillators (7.5/16 MHz), 32-bit SPI interface with 50+ configuration/diagnostic registers, two-channel PSI-5 asynchronous remote sensor interface (L9678P-S variant), four-channel DC sensor interface, and watchdog timer with retry logic - all operating across -40 °C to +95 °C with minimum 6 V supply voltage.

Key Specifications

Pinout & Package

LQFP64 (10 × 10 × 1.4 mm) package with exposed thermal pad; RoHS-compliant, AEC-Q100 Grade 2 qualified.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar airbag system controller applications.

Compared with MC33816 and RAA215200, the L9678P uniquely combines ERBOOST regulation, PSI-5 interface, ISO9141 transceiver, and COVRACT switch in one AEC-Q100 package - enabling complete airbag controller functionality with minimal external components.

Availability

L9678P is available at Aetrix Electronics and suitable for low-end airbag systems, battery cut-off systems, and pyro fuse management requiring stable component supply through June 2026 production lifecycle.

Supply support for L9678P 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 of functional safety-certified components.

The L9678P belongs to ST's SAFETY line of ASIL-B-compliant airbag system ICs, designed specifically for cost-optimized, high-reliability occupant restraint controllers in entry-level vehicles.

FAQ

What is the purpose of the COVRACT pin?

The COVRACT pin controls the internal crossover switch used for battery cut-off during crash events. It enables direct connection to external MOSFET gates or optocouplers to isolate the 12 V battery, with guaranteed <3 Ω on-resistance and 600 mA continuous current capability - meeting UNECE R100 isolation requirements without external drivers.

Does the L9678P support both PSI-5 and ISO9141 simultaneously?

Yes - the L9678P integrates a dedicated ISO9141 (K-line) transceiver and, in the L9678P-S variant, two asynchronous PSI-5 channels. Both interfaces operate concurrently: ISO9141 handles diagnostic communication with the vehicle ECU, while PSI-5 acquires real-time acceleration data from remote sensors - with independent clock domains and fault-isolated signal paths.

How does the ERBOOST regulator achieve 23 V or 33 V output selection?

Output voltage selection is configured via SPI register SYS_CFG[ERBOOST_SEL]. The internal 1.882 MHz boost controller adjusts duty cycle and feedback reference to deliver either 23 V ±5% or 33 V ±5% to the external energy reserve capacitor. Selection is non-volatile and retained across power cycles when configured in OTP memory.

What diagnostic coverage does the L9678P provide for squib circuits?

The L9678P performs five distinct squib diagnostics: resistance measurement (Rmeasure), short-to-battery (STB), short-to-ground (STG), leakage current detection, and high/low-side FET integrity testing. All are executed via dedicated analog front-end circuitry and reported through LPDIAGSTAT and LPDIAGREQ registers - supporting ASIL-B fault coverage per ISO 26262 Annex G.