L9679P datasheet(39/272 Pages) STMICROELECTRONICS

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L9679P

Start-up and power control

271

is done through the System Control (SYS_CTL) register. Boost converter diagnostics

include over voltage and under voltage and the circuit is fully protected against shorts. Boost

fault status is available through the SPI in Fault Status Register (FLTSR). The integrated

FET featuring the boost switch is protected against short to battery by means of a thermal

shutdown circuit. When thermal fault is detected the FET is switched off and latched in this

state until the related fault flag ERBST_OT in the FLTSR register is read. In case of loss of

BSTGND ground the FET is not turned on. Loss of ground can be detected also when the

FET is off thanks to a pull-up current present on the BSTGND pin. The FET will be

automatically reactivated as soon as ground connection is restored. Over-voltage protection

from load dump and inductive flyback is provided via an active clamp and an ER_Boost

disable circuitry, see Figure 11.

Figure 11. ERBOOST regulator block diagram

Normal run time power for the system is provided directly from the battery input, not from the

boost. Boost energy is available to the system through the energy reserve crossover switch

once battery is lost or a commanded system shutdown is initiated.

L9679P 데이터시트(PDF) 39 Page - STMicroelectronics