Production Data
WM8352
14.9 LDO REGULATOR OPERATION
The WM8352 provides four identical LDO voltage regulators to generate accurate, low-noise supply
voltages for various system components. The LDOs 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 LDO regulators are dynamically programmable. Each regulator output is current-limited; the
output voltage is automatically throttled back if the load current exceeds the limit.
A single supply pin (LDOVDD) provides the core supply for all four LDOs. The input voltage
connection to LDO1 and LDO2 is provided on the VINA pin. The input voltage connection to LDO3
and LDO4 is provided on the VINB pin. These input voltages can be provided from one of the DC-DC
Converters or from the LINE voltage.
Note that separate voltage regulators are provided to generate the backup supply VRTC and the
microphone bias voltage MICBIAS.
The connections to LDO Regulator 1 are illustrated in Figure 71. The equivalent circuit applies to
LDO2, LDO3 and LDO4.
Figure 71 LDO Regulator Connections
An input and output capacitor are recommended for each LDO Regulator, as illustrated above. See
Section 29.5 for details of the recommended external components.
PD, February 2011, Rev 4.4
143
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
