WM8311 datasheet(37/302 Pages) WOLFSON

37 / 302 page

Pre-Production

WM8311

PP, May 2012, Rev 3.1

The WM8311 monitors the DC-DC Converters and LDOs during the ON sequence to ensure that the

required circuits have powered up successfully before proceeding to the next timeslot. The nominal

timeslot durations are extended if necessary in order to wait for the selected DC-DC Converters or

LDOs to power up. If the ON sequence has not completed within 2 seconds of starting the transition,

then a Power Sequence Failure has occurred, resulting in the OFF state being forced.

Note that, when the OFF state is forced as a result of a Power Sequence failure, all converters and

regulators will be shut down. The shutdown sequence is not controlled in this case; all enabled

converters and regulators will be disabled immediately on detection of a Power Sequence failure.

The most recent ON or WAKE event can be determined by reading the bits in the “ON Source”

Source” register, R400Fh.

The “ON Source” register is updated when a new ON event occurs. The “OFF Source” register is

updated when a new OFF event occurs. Note that some Reset conditions (see Section 24) result in

an OFF transition followed by an ON transition; these events are recorded as Reset events in the “ON

Source” register.

The ON Source and OFF Source register fields are defined in Table 2.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R16387

(4003h)

Power State

CHIP_ON

Indicates whether the system is

ON or OFF.

0 = OFF

1 = ON (or SLEEP)

OFF can be commanded by

writing CHIP_ON = 0.

Note that writing CHIP_ON = 1 is

not a valid ‘ON’ event, and will not

trigger an ON transition.

CHIP_SLP

Indicates whether the system is in

the SLEEP state.

0 = Not in SLEEP

1 = SLEEP

WAKE can be commanded by

writing CHIP_SLP = 0.

SLEEP can be commanded by

writing CHIP_SLP = 1.

11:10

PWRSTATE_DLY

Power State transition delay

00 = No delay

01 = No delay

10 = 1ms

11 = 10ms

R16398

(400Eh)

ON Source

ON_TRANS

Most recent ON/WAKE event type

0 = WAKE transition

1 = ON transition

ON_GPIO

Most recent ON/WAKE event type

0 = Not caused by GPIO input

1 = Caused by GPIO input

ON_SYSLO

Most recent WAKE event type

0 = Not caused by SYSVDD

1 = Caused by SYSLO threshold.

Note that the SYSLO threshold

cannot trigger an ON event.

ON_PEN_DOWN

Most recent WAKE event type

0 = Not caused by Pen Down

1 = Caused by Touch Panel Pen

Down detection.

Note that the Pen Down detection

cannot trigger an ON event.

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