Production Data
WM8352
29.4.3 DC-DC (STEP-UP) CONVERTERS - USB MODE
USB mode is selected by setting DCn_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) Converters in this mode are illustrated in Figure 91.
Figure 91 DC-DC (Step-Up) Converters External Components - USB Mode
In the USB mode, the DC-DC (Step-Up) Converters use 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) Converters may be configured as USB OTG supplement by setting
USB_MSTR = 1 as described in Section 17.4. (The DC-DC Converters USB mode must also be
selected by setting DCn_FBSRC[1:0] = 11). The output of the applicable 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) CONVERTERS RECOMMENDED COMPONENTS
Wolfson recommends the following external components for use with DC-DC Converters 2 and 5.
Note that the choice of output capacitor should be determined as described in Section 29.4.1.
COMPONENT
VALUE
10μH
0.47μF
4.7μF
10μF
PART NUMBER
SIZE
L
Taiyo Yuden NR4012T100M (0.7A)
Murata GRM21BR71E474KC01L
Murata GRM188R60J475KE19D
Murata GRM219R60J106KE19B
Murata GRM188R60J475KE19D
COUT
0805
0603
0805
0603
CIN
4.7μF
FET
On Semiconductor NTHD4N02F
N-Channel FETKY
Table 159 Recommended External Components - DC-DC2 and DC-DC5
PD, February 2011, Rev 4.4
331
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
