L9680 datasheet(47/286 Pages) STMICROELECTRONICS

47 / 286 page

DS11615 Rev 7

47/286

L9680

Start-up and power control

285

In case of loss of 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 a SYNC_Boost

disable circuitry, see Figure 21.

Figure 21. SYNCBOOST regulator block diagram

Figure 22. SYNCBOOST regulator state diagram

Comp

SYNCBST

Driver &

Control

CLAMP

syncbst _en

SYNCBSTSW

SYNCBOOST

BSTGND

SYNCBST_CLAMP _ENTH

SYNCBST_

DISABLE TH

VIN

GAPGPS02266

GAPGPS02267

SYNCBOOST ON

SYNCBOOST OFF

SYNC BOOST

power mode control

(SYNCBST_OT = 1

AND

“deployment not in progress”)

SYNCBST OT

Reset T1

T1 Timeout

SYNC_BST_STBY

Start T1 1ms

SYNCBST_OT = 0

POWER-OFF_MODE

OR SLEEP_MODE

SYNCBOOST

TEMP OFF

(Transition from RUN_STATE to ER _STATE )

AND (SYS_CTL(KEEP_SYNCBST_ON)=0)

(rising edge of SYNCBST_RESTART AND

SYS_CTL(RESTART_SYBST_SEL)=1)

(VIN_SYNCBST_RESTART =1 AND

SYS_CTL(RESTART_SYBST_SEL)=0)

(exit from ER_STATE )

(SPI received SYS_CTL(KEEP_SYNCBST_ON)=1)

VIN > VINGOOD

AND

SYS_CTL(SYNCBST_EN) =1

AND

BSTGND_loss = 0

AND

SYNCBST_DISABLE=0

AND

SYNCBST_OT = 0

AND

VINSYNC_DIS = 0

AND

SYNCBST_OV = 0

VIN < VINBAD

SYS_CTL(SYNCBST_EN) =0

BSTGND_loss = 1

SYNCBST_DISABLE=1

VINSYNC_DIS=1

SYNCBST_OV = 1

SYNCBST_OT = 1

Default SYS_CTL(SYNCBST_EN) =1 at POR

Default SYS_CTL(KEEP_SYNCBST_ON)=1 at POR.

SYNCBST_RESTART = 1 when SYNCBOOST output voltage < Vsyncbst_restart_th.

VIN_SYNCBST_RESTART = 1 when VIN voltage > Vvin_syncbst_restart_th.

Change of SYS_CTL(KEEP_SYNCBST_ON) bit is automatically denied when ER_STATE is active .

In SYNCBOOST_TEMP_OFF state if SYS_CTL(KEEP_SYNCBST_ON)=1 is received we move to OFF state .

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