wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 134

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

WM8400
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POWER MANAGEMENT SUBSYSTEM
INTRODUCTION
POWER SEQUENCING AND CONTROL
The WM8400 provides 2 DC-DC converters and 4 LDO regulators which each deliver high efficiency
across a wide range of line and load conditions. These power management components are
designed to support application processors and associated peripherals. They are also suitable for
providing power to the analogue and digital functions of the on-board CODEC and GPIO features of
the WM8400.
The output voltage of all the converters is programmable in software through control registers. The
DC-DC converters and two of the LDOs can also be configured through hardware pins under start-up
conditions.
The power control sequencer can be used to enable the on-board DC-DC converters and two of the
LDO regulators in accordance with the desired start-up sequence. It can also be used to activate
other system peripherals if required.
The WM8400 can be commanded to Soft Sleep mode, from which the CODEC and the converters
may be placed in a low power condition, whilst still permitting a rapid return to the previous operating
states. The WM8400 also supports a Deep Sleep mode, in which the CODEC is shut down entirely
and the converters are placed in a user-configurable low power state.
POWER MANAGEMENT POWER DOMAINS
Operation of the power management functions requires appropriate power supplies to be connected
to the HBVDD, MBVDD and LINE power domains. These supplies are referenced to GND. The
operating ranges for these supplies are detailed in the “Recommended Operating Conditions”
section.
HBVDD and MBVDD are power connections for the digital functions within the Host Buffer and Multi
Media Buffer processors. LINE is the power supply input for support functions such as the UVLO,
Reset and Oscillator functions. VINT is a regulated supply generated from the LINE input.
See ‘”Applications Informations for further details of external components required for VINT.
ENABLING THE DEVICE
The WM8400 is enabled by setting a logic high level on the NPDN pin (referenced to the HBVDD
power domain). On start-up, a controlled sequence of events is initiated. When NPDN is set low to
disable the device, a ‘soft shutdown’ is executed, where the CODEC and Power Management
functions are disabled in a controlled manner, avoiding audio pops and other undesirable effects.
Note that the NPDN pin should not be connected directly to LINE as this will result in excessive
leakage current through the device.
The PWRGOOD is used to indicate whether the device is in an active state or not. During device
start-up or under a fault condition the PWRGOOD will be held in a logic low.
See “Chip Reset” for other requirements associated with device Start-Up.
See “Applications Information” for details of external components required to enable correct
operation of the WM8400.
PP, April 2009, Rev 3.0
Pre-Production
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