STMicroelectronics L9659TR

Overview

L9659TR from STMicroelectronics is an octal high-voltage squib driver ASIC designed for automotive airbag safety systems. It integrates eight independently controllable high-side/low-side MOSFET pairs, supports SPI-selectable firing currents (1.2 A min/2 ms, 1.75 A min/1.0 ms, or 1.75 A min/0.65 ms), operates across VRES = 7–37 V, and delivers full diagnostic coverage including squib short-to-ground/battery detection and analog resistance measurement.

For engineers reviewing the L9659TR datasheet, L9659TR pinout, L9659TR application, or L9659TR equivalent, this device requires attention to VRES voltage range compliance, fire-enable timing coordination across four FEN inputs, SPI register mapping for diagnostic mode selection, and thermal derating above 130 °C junction temperature during deployment cycles.

Technical Context

The L9659TR implements a dual-MOSFET per channel architecture with independent high-side (SQHx) and low-side (SQLx) drivers, enabling flexible squib firing configurations and robust open/short diagnostics. Its internal BCD5 process supports simultaneous 8-channel deployment while maintaining <25 µs POR de-glitch timing and 5.5 MHz SPI interface operation.

Diagnostic capability is embedded at silicon level: analog output (AOUT) provides squib resistance measurement, SPI registers report fault status (e.g., squib short-to-ground), and HSS/VRESx selection enables per-channel voltage margin testing under load dump conditions up to 37 V.

Key Specifications

Pinout & Package

Package: LQFP64 (10 mm × 10 mm × 1.4 mm), RoHS-compliant, ST proprietary BCD5 (0.65 µm) technology.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar squib driver applications.

Compared with MC33816 and RAA230120, the L9659TR uniquely combines full 8-channel simultaneous firing, per-channel VRES/GND isolation, analog AOUT-based resistance measurement, and 37 V VRES tolerance - making it optimal for high-integrity, multi-squib automotive safety systems requiring ASIL-D-ready diagnostics.

Availability

L9659TR is available at Aetrix Electronics and suitable for automotive airbag control units, side-curtain deployment modules, driver knee airbag actuators, and passenger pretensioner systems requiring stable component supply across extended vehicle lifecycles.

Supply support for L9659TR 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, specializing in automotive, industrial, and power management ICs with broad IP portfolio and AEC-Q100-qualified manufacturing.

The L9659TR belongs to ST's automotive safety ASIC product line, engineered specifically for ASIL-B/C-compliant airbag and restraint system controllers requiring high-current squib driving and comprehensive hardware-level diagnostics.

FAQ

What is the maximum VRES voltage the L9659TR can safely handle during deployment?

The L9659TR supports VRES voltages from 7 V to 37 V during deployment, with absolute maximum rating of 40 V. Operation above 37 V is permitted only for up to 48 hours under degraded conditions; sustained deployment above 37 V risks permanent damage. The device guarantees 1.75 A minimum firing current at 37 V with appropriate VRES capacitance (≥68 nF per pair).

How does the L9659TR perform squib resistance measurement?

The L9659TR uses its AOUT pin (Pin 48) to deliver a current proportional to squib resistance, referenced to AGND (Pin 47). This analog output is scaled by the external IREF resistor (10 kΩ ±1%) and read by an external ADC. Diagnostic modes accessible via SPI allow isolation of individual channels and suppression of parasitic paths during measurement.

Can the L9659TR deploy all eight channels simultaneously, and what are the power supply implications?

Yes, the L9659TR supports simultaneous deployment of all eight channels. This requires adequate VSDIAG supply (7–37 V) and sufficient VRESx decoupling capacitance (≥68 nF per pair). Total peak current draw exceeds 14 A (8 × 1.75 A), so PCB layout must minimize inductance on VRESx and GNDx paths to avoid voltage droop-induced misfires.

What diagnostic faults are reported in SPI registers, and how are they accessed?

SPI registers report squib short-to-ground, short-to-battery, open-circuit, and high-resistance faults per channel, plus MOSFET failure indicators. These are accessed via dedicated diagnostic mode commands (e.g., "Diagnostic Mode 3" per Table 13) and returned in MISO responses. Fault status is latched until cleared by host MCU write, supporting fail-safe system behavior.