wm8351 Wolfson Microelectronics plc, wm8351 Datasheet - Page 126

• Manufacturer Part Number: wm8351
• Description: Wolfson Audioplus? Stereo Codec With Power Management
• Manufacturer: Wolfson Microelectronics plc

WM8351
14.6 CONFIGURING THE DC-DC CONVERTERS
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The configuration of the DC-DC converters 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.
14.6.1
The DC-DC Converters can be enabled in software using the register fields defined in Table 70. All
DC-DC converters include a soft-start feature that helps to reduce the inductor current at start up. In
order to further reduce supply in-rush current, individual converters should be programmed to start in
different time slots within the start-up sequence.
In the WM8351 ACTIVE state, the DC-DC Converters can be enabled in software using the
DCn_ENA bits. Setting these bits whilst in the Pre-Active state (see Figure 65) will not immediately
enable the corresponding DC-DC converter; these bits will only become effective once the WM8351
has reached the ACTIVE state.
Each Converter may be programmed to switch on in a selected timeslot within the start-up sequence.
The WM8351 will set the DCn_ENA field for any DC-DC converter that is enabled during the start-up
sequence. Note that setting the DCn_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 Converter may be programmed to switch off in a selected timeslot within the shutdown
sequence. If a Converter is not allocated to one of the 14 shutdown timeslots, it will be disabled when
the WM8351 enters the OFF state.
Note: n is a number between 1 and 6 that identifies the individual DC-DC converter
R13 (0Dh) or
R176 (B0h)
Note: These bits can be accessed through R13 or through R176. Reading from or writing to either
register location has the same effect.
R181 (B5h) for
DC-DC1
R184 (B8h) for
DC-DC2
R187 (BBh) for
DC-DC3
R190 (BEh) for
DC-DC4
Note: n is number between 1 and 4 that identifies the individual DC-DC converter
Table 70 Enabling and Disabling the DC-DC Converters
14.6.2
The DC-DC converters are controlled by an internally generated clock signal from the RC Oscillator
with a constant frequency of around 2.048MHz for DC-DC 1, 3 and 4, and a constant frequency of
around 1.024MHz for DC-DC 2.
ADDRESS
DC-DC CONVERTER ENABLE
CLOCKING
0,1,2,3
13:10
BIT
9:6
DCn_ENA
DCn_ENSLO
T [3:0]
DCn_SDSLO
T [3:0]
LABEL
Dependant on
Dependant on
CONFIG[1:0]
CONFIG[1:0]
DEFAULT
settings
settings
0000
DCDCn converter 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.
Time slot for DC-DCn 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
1111 = Start up on entering ACTIVE
Time slot for DC-DCn shutdown.
0000 = Shut down on entering OFF
0001 = Shutdown in time slot 1
…. (total 14 slots available)
1110 = Shutdown in time slot 14
1111 = Shut down on entering OFF
DESCRIPTION
PD, June 2009, Rev 4.1
Production Data
126