wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 148

• 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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LDO REGULATOR OPERATION
CURRENT REFERENCE
The WM8400 provides four LDO Regulators. All of these are dynamically programmable in software;
LDO1 and LDO2 may also be enabled and configured in hardware.
In a typical application, LDO3 and LDO4 are suitable for powering the CODEC circuits. In such a
case, LDO3 could supply 3.0V to AVDD/HPVDD and LDO4 could supply 1.8V to DCVDD.
The principal characteristics of the LDOs are summarised in Table 96.
Table 96 LDO Regulator Characteristics
The connections to the LDO Regulator 1 are illustrated in Figure 86. The equivalent circuit applies to
LDO2, LDO3 and LDO4 also.
Figure 86 LDO Regulator Connections
An input and output capacitor are recommended for each LDO Regulator, as illustrated above. See
“Applications Information” for details of these external components.
The Power Management functions on the WM8400 use an integrated current reference circuit. This
circuit requires the connection of an external resistor to the RIREF pin. A 100kΩ resistor is
recommended - see “Applications Information”.
Converter Type
Input Voltage Range
Output Voltage Range
Maximum Load Current
Drop-Out Voltage (Vout < 1.8V)
Drop-Out Voltage (Vout > 1.8V)
PARAMETER
Low Drop-Out Regulator (LDO)
2.5V to 5.5V
0.9V to 3.3V
150mA (short term output up to 250mA is possible)
700mV (typical)
200mV (typical)
VALUE
PP, April 2009, Rev 3.0
Pre-Production
148