WM8321 Datasheet, PDF (94/253 Pages) Wolfson Microelectronics plc – Processor Power Management Subsystem

WM8321
Production Data
15.15.2 LDO REGULATORS
The LDO Regulators are configurable circuits which generate accurate, low-noise supply voltages for
various system components. The LDO Regulators are dynamically programmable and can be re-
configured at any time. Two low power modes are provided for the general purpose LDOs 1-6; a
single low power mode is provided for the analogue LDOs 7-10; this enables the overall device power
consumption to be minimised at all times.
The LDOs 1-10 can also operate as current-limited switches, with no voltage regulation; this is useful
for ‘Hot Swap’ outputs, i.e. supply rails for external devices that are plugged in when the system is
already powered up - the current-limiting function prevents the in-rush current into the external device
from disturbing other system power supplies.
The input voltage to these LDOs is provided on pins LDO3VDD, LDO4VDD, LDO5VDD, LDO6VDD
for LDO3 through to LDO6 respectively. The other LDO inputs are shared on pins LDO1_2VDD,
LDO7_8VDD and LDO9_10VDD for each corresponding pair of LDOs.
The LDO input supply pins may be connected to the PVDD power supply voltage node, or else can be
connected to the output pin of one of the DC-DC buck converters. Note that the LDO input supply
pins must not be connected to a voltage higher than PVDD.
LDO11 is a configurable LDO intended for ‘always-on’ functions external to the WM8321. The
WM8321 contains a further two non-configurable LDOs which support internal functions only.
The connections to LDO Regulator 1 are illustrated in Figure 22. The equivalent circuit applies to
LDO2 through to LDO10.
Figure 22 LDO Regulator Connections
An input and output capacitor are recommended for each LDO Regulator, as illustrated above.
See Section 30.4 for details of specific recommended external components.
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PD, February 2012, Rev 4.0
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