wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 139

• Manufacturer Part Number: wm8400
• Description: Wolfson Audioplustm Hi-fi Audio Codec And Power Management Unit For Mobile Multimedia
• Manufacturer: Wolfson Microelectronics plc

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Pre-Production
DC-DC CONVERTER OPERATING MODES
The DC-DC Converters have three distinct operating modes, which are as follows:
The DC-DC Converter operating modes are selected using the register bits described in Table 84.
In Active mode, the DC-DC Converters operate to their highest level of performance. The DC-DC
Converters will automatically select PWM or Pulse-Skipping operation according to the load
condition. This enables the power efficiency to be maximised across a wide range of load conditions.
It is possible to force the Converters to use the higher performance PWM mode by setting
DC1_FRC_PWM or DC2_FRC_PWM.
In Standby/Hysteretic Mode, the DC-DC Converters use a hysteretic mode of operation in order to
reduce power consumption. The load regulation is degraded in this mode of operation.
In Hibernate Mode, the DC-DC Converters are either disabled or are reconfigured as low power
LDOs, according to user settings.
Table 84 DC-DC Converter Operating Modes
When the WM8400 is placed in Soft Sleep or Deep Sleep Modes (see Table 79), this may take
precedence over the _SLEEP and _ACTIVE register selections. In summary, the DC-DC Converter
Operating mode is selected according to the following truth table for DC1. The equivalent logic
applies for DC2 Converter.
Note that the DC-DC Converters must also be enabled in hardware or software as described earlier.
Table 85 DC1 Converter Operating Mode Selection
R70 (46h)
R71 (47h)
R72 (48h)
R73 (49h)
Active
Soft Sleep
Deep Sleep
OPERATING MODE
REGISTER
ADDRESS
WM8400
-
-
-
Active
Standby/Hysteretic
Hibernate
BIT
14
13
13
14
13
13
DC1_ACTIVE
DC1_SLEEP
DC1_FRC_PW
M
DC2_ACTIVE
DC2_SLEEP
DC2_FRC_PW
M
DC1_SLEEP
LABEL
X
0
0
1
0
1
DEFAULT
1b
0b
0b
1b
0b
0b
DC1_ACTIVE
DC1 Active Mode select
0 = Standby/Hysteretic Mode selected
1 = Active Mode selected
DC1 Sleep Mode select
0 = Not selected
1 = Selected
DC1 Force PWM operation
0 = Not selected
1 = PWM operation forced
DC2 Active Mode select
0 = Standby/Hysteretic Mode selected
1 = Active Mode selected
DC2 Sleep Mode select
0 = Not selected
1 = Selected
DC2 Force PWM operation
0 = Not selected
1 = PWM operation forced
X
X
X
X
0
1
DESCRIPTION
Standby/Hysteretic
Active
Hibernate
Standby/Hysteretic
Hibernate
Hibernate
PP, April 2009, Rev 3.0
OPERATING MODE
DC1
WM8400
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