L9963T datasheet(22/45 Pages) STMICROELECTRONICS

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Figure 14. Wake up sequence

DIS_PULLDOWN

3.3.2

Reset state

When VDD is below the value triggering the power up, the device is not functional. No operation is possible while

under reset.

3.3.3

Stand-by state

This state is entered either from Reset state or from Regulators disabling state:

•

Transition from Regulators disabling state only occurs upon DIS low → high transition while L9963T is in

Normal state. DIS input signal is filtered in both analog (TRC_DELAY) and digital (TDIS_DEGLITCH) domains.

•

Transition from Reset state only occurs upon first power up, after POR_STBY release.

While in standby, the logic checks the FirstPowerupDone latch, whose reset value is ‘0’ upon first power up:

•

In case FirstPowerupDone = 0, the first power up has never been accomplished. Hence, the device moves

to Regulators enabling state, regardless of any wake up source state.

•

In case FirstPowerupDone = 1, the first power up has already been accomplished. Hence, the device is

kept in Stand-by state and eventual transitions are determined by the wake up sources.

When a wake up source is asserted, it triggers the wake up sequence that will move L9963 to Regulators

enabling state. The possible wakeup sources are:

•

The deassertion of DIS pin, pulled down by an external open drain source (TRC_DELAY + (1/ fSTBY_OSC) filter

applies).

•

The detection of at least NMIN_ISO_WUP_EDGES pulses within TWAKEUP_TIMEOUT_ISO on the ISOline.

3.3.4

Regulators enabling state

This is a transitional state reached from Stand-by state.

While L9963T is in this state, it enables the V3V3 regulator and the OSCI_MAIN.

During this process lasting TWAKEUP the device must not be sensitive to DIS pin, SPI interface and ISOline

sources.Once a wake up sequence is started, it cannot be interrupted.

L9963T

Device functional states

DS13590 - Rev 4

page 22/45

L9963T Datasheet(PDF) 22 Page - STMicroelectronics