wm8350 Wolfson Microelectronics plc, wm8350 Datasheet - Page 331

• Manufacturer Part Number: wm8350
• Description: Wolfson Audioplus? Stereo Codec With Power Management
• Manufacturer: Wolfson Microelectronics plc

Production Data
29.2 DC-DC (STEP-DOWN) CONVERTER EXTERNAL COMPONENTS
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The recommended connections to the DC-DC (Step-Down) Converters are illustrated in Figure 88.
Figure 88 DC-DC (Step-Down) Converters 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. It should be noted that some
components’ capacitance changes significantly depending on the DC voltage applied. Ceramic X7R
or X5R types are recommended.
The choice of output capacitor for DC-DC1 and DC-DC6 varies depending on the required transient
response. A value of 30μF is recommended in the first instance. Larger values (up to 100μF) may be
required for optimum performance under large load transient conditions. Smaller values (down to
10μF) may be sufficient for a steady load in some applications.
For layout and size reasons, users may choose to implement large values of output capacitance by
connecting two or more capacitors in parallel.
To ensure stable operation, the register fields DC1_CAP and DC6_CAP must be set according to the
output capacitance, as detailed in Table 155.
Table 155 Register Control for DC-DC1 and DC-DC6 Output Capacitor
When selecting a suitable output inductor, the inductance value and the saturation current must be
compatible with the operating conditions of the converter.
The magnitude of the inductor current ripple is dependant on the inductor value and can be
determined by the following equation:
R180 (B4h)
R195 (C3h)
ADDRESS
15:1
15:1
BIT
4
4
DC1_CAP
DC6_CAP
LABEL
DEFAULT
00
00
DC-DC1 Output Capacitor
00 = 10uF, 30uF, 45uF
01 = 60uF, 85uF
10 = Not used
11 = 100uF
DC-DC6 Output Capacitor
00 = 10uF, 30uF, 45uF
01 = 60uF, 85uF
10 = Not used
11 = 100uF
DESCRIPTION
PD, June 2009, Rev 4.1
WM8350
331