L9678P datasheet(26/203 Pages) STMICROELECTRONICS

26 / 203 page

Start-up power control

L9678P, L9678P-S

26/203

DocID029274 Rev 3

Figure 8. Normal power down sequence - VIN controlled

4.2.6

Operating states

Different states can be identified while operating the device. These states allow safe and

predictable initialization, test, operation and end of line disposal of the part (scrapping).

As soon as the RESET signal is de-asserted at the beginning of the ACTIVE mode, the

microcontroller powers up. At this stage, L9678P is in the Init state: during this state the

device must be initialized by the controller. In particular, the watchdog timer window can be

programmed during this state.

When the watchdog service begins (upon the first successful watchdog feed), the device

switches to Diag state for diagnostics purposes. The remaining configuration of the device is

allowed in this state, in particular for safing records and deployment masks. Several tests

are also enabled while in this state and all these tests are mutually exclusive to one another.

HS and LS switch tests of the squib drivers can only be processed during this diag state.

Also high side safing FET can only be run during this state. When not in diag state, any

L9678P 데이터시트(PDF) 26 Page - STMicroelectronics