WM8351 datasheet(134/330 Pages) WOLFSON

134 / 330 page

WM8351

Production Data

PD, April 2012, Rev 4.5

134

14.7 CONFIGURING THE LDO REGULATORS

The configuration of the LDO Regulators is described in the following sections. Some of the control

fields form part of the Custom Mode configuration settings and therefore will not require to be set in

software in some applications.

14.7.1

LDO REGULATOR ENABLE

The LDO Regulators can be enabled in software using the register fields defined in Table 82. To

reduce supply in-rush current, individual regulators should be programmed to start in different time

slots within the start-up sequence.

In the WM8351 ACTIVE state, the LDO Regulators can be enabled in software using the LDOn_ENA

bits. Setting these bits whilst in the Pre-Active state (see Figure 65) will not immediately enable the

corresponding LDO Regulators; these bits will only become effective once the WM8351 has reached

the ACTIVE state.

Each Regulator may be programmed to switch on in a selected timeslot within the start-up sequence.

The WM8351 will set the LDOn_ENA field for any LDO Regulator that is enabled during the start-up

sequence. Note that setting the LDOn_ENSLOT fields in software is only relevant to the Development

Mode, as these fields are assigned preset values in each of the Custom Modes.

Each Regulator may be programmed to switch off in a selected timeslot within the shutdown

sequence. If a Regulator is not allocated to one of the 14 shutdown timeslots, it will be disabled when

the WM8351 enters the OFF state.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R13 (0Dh) or

R176 (B0h)

DC-DC / LDO

requested

LDO1_ENA

LDO1 enable

0 = disabled

1 = enabled

Note: internal conditions may prevent the

converter from actually switching on -

see DCDC/LDO Status register for actual

converter status.

LDO2_ENA

LDO2 enable

0 = disabled

1 = enabled

Note: internal conditions may prevent the

converter from actually switching on -

see DCDC/LDO Status register for actual

converter status.

LDO3_ENA

LDO3 enable

0 = disabled

1 = enabled

Note: internal conditions may prevent the

converter from actually switching on -

see DCDC/LDO Status register for actual

converter status.

LDO4_ENA

LDO4 enable

0 = disabled

1 = enabled

Note: internal conditions may prevent the

converter from actually switching on -

see DCDC/LDO Status register for actual

converter status.

Note:

These bits can be accessed through R13 or through R176. Reading from or writing to either

R201 (C9h)

for LDO1

R204 (CCh)

for LDO2

13:10

LDOn_ENSL

OT [3:0]

0000

Time slot for LDOn start-up

0000 = Disabled (do not start up)

0001 = Start-up in time slot 1

… (total 14 slots available)

1110 = Start-up in time slot 14

WM8351 Datasheet(PDF) 134 Page - Wolfson Microelectronics plc

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