WM8310 datasheet(281/291 Pages) WOLFSON

281 / 291 page

Pre-Production

WM8310

PP, May 2012, Rev 3.1

281

30.4 DC-DC (STEP-UP) CONVERTER EXTERNAL COMPONENTS

The recommended connections to the DC-DC (Step-Up) Converter are illustrated in Figure 35.

Figure 35 DC-DC (Step-Up) Converters External Components

In the constant current mode, the DC-DC Converter output voltage is controlled by the WM8310 in

order to achieve the required current in ISINK1 or ISINK2. The required current is set by the

CSn_ISEL register fields, as described in Section 16.2.2. A typical application for this mode would be

a white LED driver, where several LEDs are connected in series to achieve uniform brightness.

The DC-DC (Step-Up) Converter is capable of generating output voltages of up to 30V. The maximum

output voltage is determined by the two external resistors R1 and R2, which form a resistive divider

between load connection and the voltage feedback pin DC4FB. The maximum output voltage is set

as described in the following equation:

Setting R2 to 47kΩ is recommended for most applications; R1 can be calculated using the following

equation, given the required output voltage:

R1 = R2 . (2VOUT –1)

Note that the resistors determine the maximum output voltage. The actual voltage will be determined

by the selected ISINK current, subject to the device limits.

When selecting a suitable capacitor, 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. The choice of output capacitor for DC-DC4 varies depending on the required output

voltage. See Table 110 for further details.

WM8310 Datasheet(PDF) 281 Page - Wolfson Microelectronics plc