wm8351 Wolfson Microelectronics plc, wm8351 Datasheet - Page 130

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

WM8351
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HIBERNATE
A summary of the Mode Control and Voltage Control for DC-DC Converter 1 is provided in Table 75.
Note that “Hibernate” in Table 75 refers to a GPIO Hibernate input or to the applicable Hibernate
signal selected by the DC1_HIB_TRIG field.
The equivalent logic applies for DC-DC 3 and 4. Note that the DC-DC Converters must also be
enabled as described in Table 70.
Table 75 DC1 Converter Operating Mode Selection
14.6.4
DC-DC Converter 2 is a boost converter which can be configured to operate in different operating
modes, using the register bits described in Table 76.
In Switch mode, the DC-DC Converter acts as a switch between VP2 and L2. The switch is enabled
(closed) by setting DC2_ENA = 1. The switch is disabled (opened) by setting DC2_ENA = 0. Note
that the switch voltage source on VP2 must be >1.2V to ensure reliable operation.
In Boost mode, the DC-DC Converter operates as a step-up converter, employing current-mode
architecture, capable of powering LED lights. The output voltage can be higher than the input
voltage, but cannot be lower. Different configurations of voltage feedback are available in boost
mode, to control the output voltage in different ways. The voltage feedback mode is selected by the
DC2_FBSRC register field.
When DC2_FBSRC = 00, the converter’s output voltage is set by two external resistors connected to
FB2. See Section 29 for Applications Information covering the selection of suitable components.
When DC2_FBSRC = 01, the converter uses the ISINKA pin as feedback and adjusts its output
voltage in order to achieve the required ISINKA current.
When DC2_FBSRC = 11, the converter’s output voltage is set by two internal resistors, resulting in a
fixed 5V output, suitable for USB interfaces.
The current-controlled configuration using ISINKA is intended for controlling a string of serially-
connected LEDs driven by the DC-DC boost converter. See Table 96 for a definition of the CS1_ISEL
register field which determines the required ISINKA current. In this mode, external resistors
connected on the FB2 pin determine the maximum output voltage. See Section 29 for Applications
Information covering the selection of suitable components.
In all configurations, the input pin VP2 must be externally wired to one of the supply rails, BATT or
LINE. Using LINE has the advantage that the converters can operate when the battery is flat,
defective or absent. Note that VP2 should not be connected to the USB supply rail.
The DC2_RMPH and DC2_RMPL bits defined in Table 76 should be set according to the desired
output voltage in order to optimise the transient response of the converter. Selecting a different value
could result in sub-harmonic oscillation of the converter.
0
0
0
1
DC-DC BOOST (STEP-UP) CONVERTER CONTROL
DC1_HIB_MODE DC1_SLEEP DC1_ACTIVE
000
001
010
011
100
101
110
111
X
X
X
X
X
X
X
X
X
0
0
1
0
0
1
0
0
1
X
X
X
X
X
X
X
X
X
0
1
0
1
0
1
Standby/Hysteretic
Standby/Hysteretic
Standby/Hysteretic
Standby/Hysteretic
Standby/Hysteretic
OPERATING
LDO Mode
LDO Mode
LDO Mode
LDO Mode
LDO Mode
Disabled
Disabled
MODE
Active
Active
Active
PD, June 2009, Rev 4.1
Production Data
VOLTAGE
DC1_VSEL
DC1_VSEL
DC1_VSEL
DC1_VSEL
DC1_VSEL
DC1_VSEL
DC1_VIMG
DC1_VIMG
DC1_VIMG
DC1_VSEL
DC1_VIMG
DC1_VSEL
DC1_VIMG
OUTPUT
N/A
N/A
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