L9679P datasheet(40/279 Pages) STMICROELECTRONICS

40 / 279 page

Start-up and power control

L9679P

40/279

DS11627 Rev 7

Figure 12. ERBOOST regulator state diagram

6.4

Energy reserve capacitor charging and discharging circuits

The energy reserve capacitor connected to VER pin can be charged in an efficient way by

means of a current generator. Its capability is 50 mA nominal, so that for example a 10 mF

capacitor can be charged in approximately 4.8 s to 24 V. The current generator is activated

or deactivated by SPI command only while in ACTIVE mode. When not in ACTIVE mode,

the generator is always switched off in order to decouple ERBOOST node voltage from VER

reserve voltage.

Figure 13. ER charge state diagram

L9679P also offers a safe control to discharge the ER capacitor by means of a fixed current

generator. This discharge can be controlled via SPI command while not in SLEEP mode.

Furthermore, this discharge circuit is mutually exclusive with the ER charging circuit, to

avoid inefficient way of controlling the charge on the VER energy reserve capacitor.

ER BST ON

(Active_mode = 1 AND

VBATMON > VBGOOD)

(ER_state=1 AND

SYS_CFG(KEEP_ERBST_ON)=1)

AND

VIN > VINGOOD

AND

SYS_CTL(ER_BST_EN)=1

AND

GNDBOOST_loss = 0

AND

ERBST_OT=0

AND

ERBST_DISABLE=0

Default SYS_CTL(ER_BST_EN) = 1

at POR = 1

[(Active_mode = 0 OR

VBATMON < VBBAD)

AND

(ER_state=0 OR

SYS_CFG(KEEP_ERBST_ON)=0)]

VIN < VINBAD

SYSCTL(ER_BST_EN) = 0

GNDBOOST_loss = 1

ERBST_DISABLE=1

ER BOOST

power mode control

ER BST OFF

ERBST_OT=1/

ER BST OT

SPI_FLTSR READ

AND

ERBST_OT=0

ERBST_OT=1

ER BST STBY

SPI_SYS_CTL(ER_BST_EN=1)

AND

ERBST_OT=0

POWER-OFF_MODE

OR SLEEP_MODE

GAPGPS02259

Active_mode = 1

AND

SYS_CTL(ER_CUR_EN[1:0]) = 01

AND

“ER CAP ESR DIAG not in progress”

Active_mode = 0

SYS_CTL(ER_CUR_EN[1:0])

SSM_Reset

ER CHARGE

OFF

ERCHARGE_OT=1

ER CHARGE

STBY

Default SYS_CTL(ER_CUR_EN[1:0]) = 00 at

SSM_RESET = 1

ERCHARGE_OT=1

SPI_SYS_CTL(ER_CUR_EN[1:0]) = 01

AND

ERCHARGE_OT=0

SPI_FLTSR READ

AND

ERCHARGE_OT=0

power mode control

ER Charge

GAPGPS02260

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