L9691-TR [STMicroelectronics]

The L9691 is an advanced airbag system chip solution targeted for the global airbag market.

High frequency power supply design optimizes system cost by using smaller and less expensive external components. All switching regulators operate at 2 MHz and all buck converters have integrated synchronous rectifiers.

The reserve capacitor is electrically isolated from the boost regulator by integrated switches and external resistors, controlling in-rush current. A capacitor discharge switch is integrated to discharge the capacitor at shutdown.

Low quiescent current permits the device to be directly connected to battery. In this mode, device start-up and shutdown are controlled through the wake-up input pin (actually, shutdown needs also dedicated SPI command too). The power supply and crossover function are controlled automatically through the internal state machine.

For systems with high feature content, two L9691 devices can be used in a master/slave configuration.

The L9691 provides two fully isolated deployment voltage regulators, using the external safing FETs as power elements in the regulator loop. Deployment voltage is set to a nominal 18V value to further optimize system cost.

Integrated safing logic uses a rolling average algorithm and decodes all sensor information within the system remote sensor SPI bus. Number of samples and thresholds are user-programmable. An alternative safing function permits arming from an external source through the Global SPI bus (E2E communication).

Dual SPI interfaces separate device global functions and remote sensors. LIN interface is available, providing OCS message decoding for passenger loop inhibition.

• AEC-Q100 qualified
• Single chip and master/slave configurations
• Boost regulator for energy reserve
  • 2 MHz operation
  • Output voltage 24 V/33 V ±6%, user-selectable, peak inductor current regulation
  • Capacitor value and ESR diagnostics
• Boost regulator for low voltage system operation
  • 2 MHz operation
  • Output voltage, 10 V ±8%, 870 mA max
• Buck regulator for remote sensor
  • 2 MHz operation
  • Output voltage, 6.5 V/8 V ±4%, 700 mA max
• Buck regulator for micro controller unit
  • 2 MHz operation
  • Output voltage, 3.3 V ±3%, 450 mA max
• Remote sensor interface and SYNC pulse supply voltage inputs and monitorings
• Linear regulator with external power PNP transistor, 5 V ±5%, 135 mA max
• Integrated energy reserve crossover switch with switch active output indicator, configured as input for slave mode operation
• Battery voltage monitor and shutdown with wake-up control
• System voltage diagnostics with integrated ADCs
• Squib/LEA deployment drivers
  • 16 channel HSD/LSD for squib load
  • 2 over 16 channels supporting LEA load
  • 2 channel couples supporting common-return connection
  • 18 V deployment voltage
  • Low, high and automatic dynamic deployment current profiles
  • R measure, STB, STG and leakage diagnostics
  • High and low side driver FET tests
  • LEA presence diagnostics
• Two isolated high side safing FET regulators and diagnostics
• Eight channel PSI-5 v2.3 remote sensor interface
• Three channel general purpose low side drivers with 0-100% PWM control
• Twelve channel hall-effect, resistive or switch sensor interface
• User-programmable safing logic and rolling average algorithm
• E2E arming procedure through Global SPI
• Temporal watchdog timer
• End-of-life disposal interface
• Temperature sensor
• 32 bit Global SPI bus interface
• 32 bit Remote Sensor SPI bus interface, SafeSPI v1.0 compatible
• LIN v2.2A interface with OCS message decoding capability
• 5.4 V min operating voltage at VIN battery input for start-up
• Full ISO 26262 compliant, ASIL-D systems ready
• Packaging 128 pin