WM8321 datasheet(64/253 Pages) WOLFSON

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WM8321

Production Data

PD, February 2012, Rev 4.0

15.4 OPERATING MODE CONTROL

15.4.1 DC-DC SYNCHRONOUS BUCK CONVERTERS

The DC-DC Converters DC-DC1 - DC-DC4 can be configured to operate in four different operating

modes. The operating modes are summarised in Table 30. For more detailed information on the DC-

DC (Buck) Converter operating modes, see Section 15.14.2.

DC-DC CONVERTER

OPERATING MODE

DESCRIPTION

Forced Continuous Conduction

Mode (FCCM)

High performance mode for all static and transient load

conditions.

Auto Mode: Continuous /

Discontinuous Conduction with

Pulse-Skipping Mode (CCM/DCM

with PS)

High efficiency mode for all static and transient load

conditions. Performance may be less than FCCM mode for

heavy load transients.

Hysteretic Mode

High efficiency mode for light static and light transient loads

only. Maximum load current is restricted; output voltage ripple

is increased.

LDO Mode

Power saving mode for light loads only. High efficiency for

ultra light loads. Low current soft-start control.

Table 30 DC-DC Synchronous Buck Converter Operating Modes

The operating mode of the DC-DC Converters in the ON power state is selected using the

DCm_ON_MODE register fields. The operating mode of the DC-DC Converters in the SLEEP power

state is selected using the DCm_SLP_MODE register fields.

When changing the operating mode of the DC-DC Converters in preparation for an increased load, a

set-up time of 100

s should be allowed for the operating mode to be established before applying the

new load.

Note that the operating mode of the DC-DC Converters may also be controlled by the Hardware

Control inputs. The Hardware Control inputs are alternate functions supported via GPIO. See

Section 15.8 for details of Hardware Control.

15.4.2 LDO REGULATORS

The LDO Regulators LDO1 - LDO10 can be configured to operate in Normal operating mode or in

Low Power mode.

The operating mode of the LDO Regulators in the ON power state is selected using the

LDOn_ON_MODE register fields. The operating mode of the LDO Regulators in the SLEEP power

state is selected using the LDOn_SLP_MODE register fields.

For the standard LDOs, LDO1 - LDO6, two different Low Power modes are provided, offering limited

load current capability and reduced quiescent current. When Low Power mode is selected in the ON

or SLEEP power states, then the LDOn_LP_MODE register bits determine which Low Power mode is

selected.

Note that the operating mode and output voltage of the LDO Regulators may also be controlled by the

Hardware Control inputs. The Hardware Control inputs are alternate functions supported via GPIO.

See Section 15.8 for details of Hardware Control.

15.5 OUTPUT VOLTAGE CONTROL

15.5.1 DC-DC SYNCHRONOUS BUCK CONVERTERS

The output voltage of the DC-DC Converters 1-4 in the ON power state is selected using the

DCm_ON_VSEL register fields. The output voltage of these converters in the SLEEP power state is

selected using the DCm_SLP_VSEL register fields.

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