wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 204

• 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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The magnitude of the inductor current ripple is dependant on the inductor value and can be
determined by the following equation:
As a minimum requirement, the DC current rating should be equal to the maximum load current plus
one half of the inductor current ripple:
To be suitable for the application, the chosen inductor must have a saturation current that is higher
than the peak inductor current given by the above equation. To maximise the converter efficiency,
the inductor should also have a low DC Resistance (DCR), resulting in minimum conduction losses.
Care should also be taken to ensure that the inductor is effective at the applicable operating
temperature.
Wolfson recommends the following external components for use with DC-DC Converters 1 and 2.
Note that the choice of output capacitor should be determined as described above.
Table 108 Recommended External Components - DC-DC1 and DC-DC2
LDO REGULATOR COMPONENT SELECTION
An input and output capacitor are recommended for each LDO Regulator. The recommended
connections are illustrated in Figure 107.
Figure 107 LDO Regulator External Components
When selecting suitable capacitors, is it imperative that the effective capacitance is within the
required limits at the applicable input/output voltage of the converter. Ceramic X7R or X5R types are
recommended.
COMPONENT
C
C
OUT
L
IN
VALUE
2.2µH
4.7µF
22µF
Murata LQM31PN2R2M00 (0.9A)
Murata GRM188R60J475KE19D
Murata GRM21BR60J226M
PART NUMBER
PP, April 2009, Rev 3.0
Pre-Production
1206
0805
0603
SIZE
204