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 18 V 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.