STMicroelectronics L9660TR

Overview

L9660TR from STMicroelectronics is a quad-channel high-side/low-side squib driver ASIC designed for automotive airbag deployment systems. It delivers configurable firing currents up to 1.75 A for durations as short as 0.65 ms across four independent channels, operates with VRES supply from 7 V to 37 V, and integrates full diagnostic capability including squib short-to-ground/battery detection and analog resistance measurement via AOUT. It is deployed in front/rear airbag control units requiring ASIL-B compliant pyrotechnic actuation.

For engineers reviewing the L9660TR datasheet, L9660TR pinout, L9660TR application, or L9660TR equivalent, key selection considerations include simultaneous multi-channel firing timing, SPI-configurable current/time profiles, integrated HSS/LSS diagnostics, and LQFP64 package compatibility with automotive PCB layout constraints.

Technical Context

The L9660TR implements four independent, digitally controlled squib deployment paths, each with dedicated high-side (SQHx) and low-side (SQLx) MOSFET drivers. Firing parameters-including current amplitude (1.2 A / 1.5 A / 1.75 A min) and pulse width (0.65 ms / 1.0 ms / 2.0 ms)-are selected via SPI configuration registers and validated under load-dump conditions (VRES = 7–37 V).

Diagnostic architecture includes real-time squib resistance measurement using IREF and AOUT, fault detection via SPI-accessible registers (short-to-battery, short-to-ground, open-circuit), and robust operation even with SQLx shorted to ground. The 5.5 MHz SPI interface supports command-driven deployment sequencing and status reporting with MISO response validation per Table 14.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC33816 and RAA278812, the L9660TR provides superior fault resilience (SQL short-to-ground operation), simpler VRES implementation (no external regulation), and integrated analog diagnostics (AOUT), making it optimal for mid-tier airbag controllers prioritizing functional safety and design simplicity over channel count or embedded communication.

Availability

L9660TR is available at Aetrix Electronics and suitable for automotive airbag control units, seat belt pretensioner modules, and side-curtain airbag systems requiring stable component supply, long-term lifecycle support, and ASIL-B compliance.

Supply support for L9660TR 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-grade ICs, power management, and smart sensing solutions.

The L9660TR belongs to ST's automotive safety ASIC product line, engineered specifically for pyrotechnic actuation in airbag systems with emphasis on diagnostic completeness, transient robustness, and ASIL-B functional safety compliance.

FAQ

What is the minimum VRES voltage required for guaranteed 1.75 A / 0.65 ms firing?

The L9660TR guarantees 1.75 A minimum firing current for 0.65 ms only when VRES is ≥7 V, as specified in Section 2.4.2 of the datasheet (DocID024714 Rev 2, p.11). Below 7 V, the device enters degraded operating mode and cannot meet this performance level - design must ensure VRES remains above 7 V during load dump per ISO 7637-2 Pulse 5a.

Can the L9660TR deploy squibs if one SQL pin is shorted to ground?

Yes. Section 3.4.4 explicitly states the L9660TR retains firing capability even when the low-side MOSFET (SQLx) is shorted to ground. This is achieved through internal diagnostic mode reconfiguration that bypasses the faulty SQL path while maintaining high-side drive and current monitoring via AOUT and IREF.

How is squib resistance measured without external components?

Squib resistance is measured using the internal IREF current source (10 kΩ ±1% reference resistor) and AOUT analog output. As described in Section 3.2.3 and Table 7, AOUT delivers a voltage linearly proportional to squib resistance (0.5–10 Ω range), referenced to AGND, eliminating need for external ADC or op-amp circuitry.

What SPI clock frequency tolerance does the L9660TR support?

The L9660TR supports a maximum SPI clock frequency of 5.5 MHz, with timing parameters defined in Table 8 (tSCLKH = 50 ns min, tSCLKL = 50 ns min). Operation outside this range risks MISO data corruption or missed command execution - designs must maintain SCLK duty cycle between 40% and 60% and limit jitter to <5 ns RMS per Figure 4.