SPSB100 datasheet(35/214 Pages) STMICROELECTRONICS

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3.7

Power-up and power-down sequence

Power-up and power-down sequences turn ON and OFF all the regulators automatically. The sequences are

executed by the device state machine as described in the Section 3.6: Functional overview - State machine and

are fully programmable through the USER-NVM space to cover a broad range of applications.

The sequences control BUCK1, 2, 3 and LDO1, 2 regulators, together with NRST pin.

3.7.1

Power-up sequence

Power-up sequence is made of 7 steps as described below.

Figure 22. Power-up sequence

Step #N:

Turn ON regulators & deassert NRESET (*) if

their PU_STEP_ON (resp

PU_STEP_DEASSERT ) = N,

no action on others.

Start

(At least one regulator has

been turned ON) AND

(PU_WAIT_PG_ON <N> = 1)

Start TimeOut counter,

wait regulators PG signal

of just turned ON

regulators

Wait for

PU_WAIT_DEL_ON <N> ms

Set N = N + 1

N ≥ 8 ?

Set PUretry = 0

Finished OK

INIT

state

PG OK before

TimeOut

reached

Execute Power -

Down sequence

Set PUretry =

PUretry + 1

(PUretry ≤

3) OR

(PU_LOOP

_FOR_EV

ER = 1) ?

Power-Up sequence

Power-Up retry loop

set N=1

End

Wait 100ms

End

Retry loop

failed

Set PUretry = 0

NVM-DL

REGfail & GoREC=1 on

any enabled regulator

Safety checks OK

AND VFBB_OK_R < VFBB < VFBB_OV

Each of BUCK-1, -2, -3, and LDO-1, -2 can be turned ON with USER-NVM bits BUCK1_PU_STEP_ENA,

BUCK2_PU_STEP_ENA, BUCK3_PU_STEP_ENA, LDO1_PU_STEP_ENA, LDO2_PU_STEP_ENA at any step

from 1 to 7. None, or more than one regulator can be turned ON at a step.

The NRST pin can be deasserted at any step from 1 to 7, with USER-NVM bits NRESET_PU_STEP_DEASSERT

independently of regulators setting. Note that the watchdog time-out starts at the step where NRST is deasserted.

After a regulator has been turned ON at step N the sequence offers the possibility to wait for power-good signal

with USER-NVM bits PU_WAIT_PG_ENA_X (X equal to steps from 1 to 7):

SPSB100

Functional description

DS14640 - Rev 1

page 35/214

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