WM8351 Datasheet, PDF (325/330 Pages) Wolfson Microelectronics plc – Wolfson AudioPlus™ Stereo CODEC with Power Management

Production Data
WM8351
29.4.3 DC-DC (STEP-UP) CONVERTER - USB MODE
USB mode is selected by setting DC2_FBSRC[1:0] = 11 as described in Section 14.6.4. This mode
generates a 5V output, suitable for USB interfaces. The recommended connections to the DC-DC
(Step-Up) Converter in this mode are illustrated in Figure 91.
Figure 91 DC-DC (Step-Up) Converter External Components - USB Mode
In the USB mode, the DC-DC (Step-Up) Converter uses an internal resistor chain to control the output
voltage. This results in a fixed 5V output, suitable for USB interfaces.
The DC-DC (Step-Up) Converter may be configured as USB OTG supplement by setting USB_MSTR
= 1 as described in Section 17.4. (The DC-DC Converter USB mode must also be selected by setting
DC2_FBSRC[1:0] = 11). The output of the DC-DC Converter should be connected to the USB pin in
order to provide voltage feedback.
The choice of Capacitors, Inductor and FET in constant current mode is the same as for the constant
voltage mode; see Section 29.4.4 for specific recommended component details.
29.4.4 DC-DC (STEP-UP) CONVERTER RECOMMENDED COMPONENTS
Wolfson recommends the following external components for use with DC-DC Converter 2. Note that
the choice of output capacitor should be determined as described in Section 29.4.1.
COMPONENT
L
C_OUT
CIN
FET
VALUE
10H
0.47F
4.7F
10F
4.7F
PART NUMBER
Taiyo Yuden NR4012T100M (0.7A)
Murata GRM21BR71E474KC01L
Murata GRM188R60J475KE19D
Murata GRM219R60J106KE19B
Murata GRM188R60J475KE19D
On Semiconductor NTHD4N02F
N-Channel FETKY
Table 159 Recommended External Components - DC-DC2
SIZE
0805
0603
0805
0603
w
PD, April 2012, Rev 4.5
325