L9679P datasheet(13/279 Pages) STMICROELECTRONICS

13 / 279 page

DS11627 Rev 7

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L9679P

Description

278

Description

The L9679P 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 L9680 devices. Safety system integration is enabled through

higher power supply currents and integrated PSI-5 satellite interface.

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 50 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.

L9679P Datenblatt(PDF) 13 Page - STMicroelectronics