L5965 datasheet(49/73 Pages) STMICROELECTRONICS

49 / 73 page

A regulator is a “reset associated regulator” if it can issue a reset signal. This is decided by OTP. RESET_B de-

asserts only when the Power Good signals of all the “reset associated regulators” are high.

When a regulator starts the power up phase, a dedicated timer, whose duration is typically of 20ms, is started: if

the Power Good signal goes high before the time expires, then the state machine moves to the next regulator in

the sequence (after the OTP programmed delay). If the time expires and the Power Good is still low, then the

correspondent regulator power up phase is considered failed.

We can have two possible scenarios, depending on the regulator type (Main, or reset associated, or Post):

•

Main BUCK power up phase fails: the FAULT pin is asserted, RESET_B is kept low and the device goes to

a safe state (called REC state) waiting for a WKUP falling down transition to go back to STANDBY.

•

Reset associated regulator or post regulator power up phase fails: the FAULT pin is asserted, RESET_B

signal is kept low and SEC_UP phase is completed for the other regulators. Once the device has moved to

the ACTIVE state, it immediately goes back to SEC_UP state to retry to turn on the failed regulator. The

retry phase is done three times: if the fail is still present, then the device moves to REC state.

L5965

RAMPUP MAIN and SEC_UP

DS12567 - Rev 3

page 49/73

L5965 Datenblatt(PDF) 49 Page - STMicroelectronics