WM8352 datasheet(326/336 Pages) WOLFSON

326 / 336 page

WM8352

Production Data

PD, February 2011, Rev 4.4

326

29.2 VOLTAGE REFERENCE (VREF) COMPONENTS

A decoupling capacitor is required between CREF and REFGND; a 2.2uF X5R capacitor is

recommended.

A reference resistor is required between RREF and REFGND; a 100k

Ω (1%) resistor is

recommended.

29.3 DC-DC (STEP-DOWN) CONVERTER EXTERNAL COMPONENTS

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 30

μF 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

μF) 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 156.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R180 (B4h)

15:14

DC1_CAP

DC-DC1 Output Capacitor

00 = 10uF, 30uF, 45uF

01 = 60uF, 85uF

10 = Not used

11 = 100uF

R195 (C3h)

15:14

DC6_CAP

DC-DC6 Output Capacitor

00 = 10uF, 30uF, 45uF

01 = 60uF, 85uF

10 = Not used

11 = 100uF

Table 156 Register Control for DC-DC1 and DC-DC6 Output Capacitor

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