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The L9680 is a chip that can be used in advanced airbag systems for mature airbag markets or in cut-off battery systems for integrated safety markets. This device is family compatible with the L9678 and L9679 devices. Safety system integration is enabled through higher power supply currents and integrated active wheel speed sensor interface. The active wheel speed interface is shared with the PSI-5 satellite interface to create a generic remote safety sensor interface compliant to both systems.
High frequency power supply design allows further cost reduction by using smaller and less expensive external components. All switching regulators operate at 1.882 MHz while buck converters have integrated synchronous rectifiers.
Additional attention is given to system integrity and diagnostics. The reserve capacitor is electrically isolated from the boost regulator by a 65 mA nominal fixed current source, controlling in-rush an additional capacitor discharge fixed current source is integrated to diagnose the reserve capacitor value and ESR. The same current sources can be used to discharge the capacitor at shutdown.
Thanks to low quiescent current, the device can be directly connected to battery. In this way, the device start-up and shutdown are controlled through the wake-up input function. The power supply and crossover function are controlled automatically through the internal state machine.
The user can select both ECU logic voltage (VCC at 3.3 V or 5.0 V) and energy reserve output voltage (at either 23 V or 33 V). Deployment voltage is set to a maximum of 25 V for all profiles and can be controlled through external safing switch circuit using the high side safing switch reference enabled through the system SPI interface or the arming logic.