WM8352 datasheet(108/336 Pages) WOLFSON

108 / 336 page

WM8352

Production Data

PD, February 2011, Rev 4.4

108

14.3 POWER SEQUENCING AND CONTROL

14.3.1

STARTUP

The WM8352 moves from OFF or HIBERNATE states to the ACTIVE state when a startup event

occurs. Startup events include:



A trigger signal on the ON pin lasting more than 40ms. The active polarity of this input is

set by the register field ON_POL.



A trigger signal on a GPIO pin configured as /WAKEUP lasting more than 40ms. The

active polarity of this input is set by GPn_CFG for the applicable GPIO pin (see

Section 20).



A trigger signal on a GPIO pin configured as PWR_ON input lasting more than 40ms. The

active polarity of this input is set by GPn_CFG for the applicable GPIO pin (see

Section 20).



Programmed ALARM from RTC module, if enabled (see Section 22).



Wall adaptor plug-in (WALL_FB rises above 4.0V).



USB plug-in (USB pin rises above 4.0V).

The start-up events are only valid provided also that the available supply voltage, sensed on the

LINE pin, is greater than the start-up threshold set by PCCMP_ON_THR, as defined in Section 18.

Start-Up by Wall adaptor plug-in occurs when the Wall Adapter feedback pin detects a voltage

greater than 4.0V. See Section 17.1 for a description of the WALL_FB pin function.

Start-Up by USB plug-in occurs when the USB voltage rises above the LINE voltage. If USB

Suspend mode is invoked, then USB plug-in starts the WM8352 on battery power, if available. When

USB Suspend Mode is not invoked, this start-up event will lead to starting the WM8352 on USB

power, and USB 100mA trickle charging of the battery is enabled.

Note that applying a battery voltage is not a start-up event, i.e. connecting a battery pack does not

start the WM8352. The WM8352 starts up on battery power if a startup event occurs and battery

power is the only power source available, provided the battery voltage is above the startup threshold.

(The start-up threshold is set by PCCMP_ON_THR, as defined in Section 18.)

In the ACTIVE state, the host processor can read the Interrupt status fields in Register R31 in order

to determine what action initiated the start-up. These fields indicate, for example, if the start-up was

due to a reset caused by an error condition, or if the start-up was caused by a PWR_ON input, or if

the start-up was caused by an RTC alarm. The first-level interrupt WKUP_INT is triggered whenever

any of the second-level interrupt events described in Table 56 is set. See Section 24 for further

details of Interrupt.

ADDRESS

BIT

LABEL

DESCRIPTION

R31 (1Fh)

Comparator

Interrupt

Status

WKUP_OFF_STATE_EINT

Indicates that the chip started from the

OFF state.

(Rising Edge triggered)

Note: This bit is cleared once read.

WKUP_HIB_STATE_EINT

Indicated the chip started up from the

hibernate state.

(Rising Edge triggered)

Note: This bit is cleared once read.

WKUP_CONV_FAULT_EINT

Indicates the wakeup was caused by a

converter fault leading to the chip being

reset.

(Rising Edge triggered)

Note: This bit is cleared once read.

WKUP_WDOG_RST_EINT

Indicates the wakeup was caused by a

watchdog heartbeat being missed, and

hence the chip being reset.

(Rising Edge triggered)

Note: This bit is cleared once read.

WM8352 Datasheet(PDF) 108 Page - Wolfson Microelectronics plc

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