L9679ETR datasheet(11/127 Pages) STMICROELECTRONICS

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Start-up and power control

5.1

Power supply overview

The L9679E IC contains an integrated power management system able to provide all necessary voltages for

internal functionality. External supplies are required to operate squib/pyroswitch drivers and RSU interfaces. The

power supply block contains the following features:

•

Two 3.3 V internal regulators for operating internal logic (CVDD) and analog circuits (VINT3V3). An

external CVDD pin is used to provide filtering capacitance to digital section supply rail. VSAT is the supply

of these two regulators. They are enabled when VSAT voltage goes above VSAT_ON threshold.

•

Sync pulse supply (VSYNC) input rail ensures a minimum voltage for operating the satellite sync signal and

running part of the squib/pyroswitch diagnostics set. At system level, it can be connected to the

SYNCBOOST output rail generated by L9679 or L9680 devices.

•

The VSAT input rail ensures the supply to operate the satellite interface. At system level, it can be

connected to the SATBUCK output rail generated by L9679 or L9680 devices.

•

The VCC input rail ensure the supply to operate the SPI interface, in particular the VCC rail is used only to

supply the MISO_G and MISO_RS output digital buffers.

5.2

Power mode control

Start-up and power down of the L9679E are controlled by the VCC pin, VSYNC pin, VSAT pin, RESET_N pin and

device status.

There are three main power modes: power-off, awake and active mode. Each power mode is described below

and represented in the state flow diagram shown in the following figure.

Figure 3. Power control state flow diagram

GADG0503181447PS

L9679E

Start-up and power control

DS12485 - Rev 8

page 11/127

L9679ETR Datasheet(PDF) 11 Page - STMicroelectronics