STPM066S datasheet(45/67 Pages) STMICROELECTRONICS

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Reset signal release is programmed via OTP: three OTP bits associate the reset signal to a regulator.

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 (Buck, or Reset associated, or Post):

•

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.

Figure 21. State machine for SEC UP

RAMPUP

BUCK

2nd REG

last REG

Active

2nd reg ok

(2nd PG = 1 before timer

expired) or time expired

last reg ok

(last PG = 1 before timer

expired) or time expired

SECUP fail <3

GADG0910180859PS

SECUP

STPM066S

RAMPUP and SEC_UP

DS12976 - Rev 2

page 45/67

STPM066S датащи(PDF) 45 Page - STMicroelectronics