L9963T datasheet(23/45 Pages) STMICROELECTRONICS

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The Regulators enabling state is left upon POR_MAIN release. Next state depends on FirstPowerupDone

latch:

•

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

toTrimming & Config Latch.

•

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

moves to Normal state.

3.3.5

Trimming and config latch

This state is entered from the Regulators enabling state the first time the device is powered up

(FirstPowerupDone = 0).

While in this state, the device must:

•

Download the OTP data.

•

Latch the configuration inputs (NSLAVE, CPHA, CPOL, SPICLKFREQ)storing them into the STBY logic

registers according to Table 7.

SPICLKFREQ comes from a set of comparators that must be checked by an internal BIST before latching the

comparator output. In case the BIST fails, a default 0 value (corresponding to the slowest SPI configuration) must

be stored into the related stand-by internal register.

Stand-by registers hold their value as long as the POR_STBY stays deasserted.

While in this state, L9963T is not sensitive to SPI/VIF activity and wake up conditions (DIS/VIF).

This phase must safely go to an end and may last a maximum time interval of TSETUP_LATCH.

After this phase has come to an end, the FirstPowerupDone latch is set to "1" in the standby logic and the device

moves to Normal state.

3.3.6

Normal state

While in this state, all references and main logic are powered. Both communication interfaces are ready for data

TX/RX activity.

This state is reached either from Trimming & Config Latch (first power up) or from Regulators enabling state

(following a normal wake up sequence):

•

When woken up by an activity on the ISOline, once Normal state is reached, the device must neglect the

DIS pin value (even if it is high) and, on the contrary, it must drive the DIS pin low for TDIS_PULLDOWN

(please note that DIS is an input/output pin). Such a strategy allows to generate an interrupt into the MCU,

or to trigger a wake up into a PMIC device. Once TDIS_PULLDOWN expires, L9963T releases the DIS pull

down and unmasks the DIS deglitched input. If the MCU or the PMIC have been correctly woken up, they

will confirm their activity by pulling down the DIS pin externally, so that L9963T will be kept in Normal state.

Otherwise, DIS will be found asserted (high) and the IC will move back to Regulators disabling state.

•

When woken up by the DIS pin itself the device must start listening to the deglitched DIS pin as soon as it

enters the Normal state.

To detect a "Go to Sleep" condition, the DIS pin status must be constantly monitored through a synchronous-

deglitch filter (TDIS_DEGLITCH, implemented in the main logic through the main oscillator).

Its effect is cascaded to the passive RC filter placed on the input comparator (TRC_DELAY).

When DIS is sensed "high", the main logic raises a signal that triggers the “Go To Sleep” sequence in the IC FSM.

L9963T moves to Regulators disabling state and finally to Stand-by state.

3.3.7

Regulators disabling state

This is a transitional state reached from Normal state during a "Go To Sleep" sequence.

While in this state, the V3V3_MAIN regulator and main oscillator enable signals are deasserted, leading to

POR_MAIN assertion and reset of the main logic.

POR_MAIN assertion marks the transition to Stand-by state.

Even if the main logic is still alive while the device is in Regulators disabling state, it must not be sensitive

to external pins (wake up sources, COM interfaces, etc.). Once started, a "Go To Sleep" sequence cannot be

interrupted.

L9963T

Device functional states

DS13590 - Rev 4

page 23/45

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