WM8281ECSSLASHR datasheet(287/392 Pages) CIRRUS

287 / 392 page

WM8281

Rev 4.0

287

SPREAD SPECTRUM FLL CONTROL

The WM8281 can apply modulation to the FLL outputs, using spread spectrum techniques. This can

be used to control the EMI characteristics of the circuits that are clocked via the FLLs.

Each of the FLLs can be individually configured for Triangle modulation, Zero Mean Frequency

Modulation (ZMFM) or Dither. The amplitude and frequency parameters of the spread spectrum

functions is also programmable, using the registers described in Table 109.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R393

(0189h)

FLL1

Spread

Spectrum

5:4

FLL1_SS_AMPL

[1:0]

FLL1 Spread Spectrum Amplitude

Controls the extent of the spread-

spectrum modulation.

00 = 0.7% (triangle), 0.7% (ZMFM, dither)

01 = 1.1% (triangle), 1.3% (ZMFM, dither)

10 = 2.3% (triangle), 2.6% (ZMFM, dither)

11 = 4.6% (triangle), 5.2% (ZMFM, dither)

3:2

FLL1_SS_FREQ

[1:0]

FLL1 Spread Spectrum Frequency

Controls the spread spectrum modulation

frequency in Triangle mode.

00 = 439kHz

01 = 878kHz

10 = 1.17MHz

11 = 1.76MHz

1:0

FLL1_SS_SEL

[1:0]

FLL1 Spread Spectrum Select

00 = Disabled

01 = Zero Mean Frequency (ZMFM)

10 = Triangle

11 = Dither

R425

(01A9h)

FLL2

Spread

Spectrum

5:4

FLL2_SS_AMPL

[1:0]

FLL2 Spread Spectrum Amplitude

Controls the extent of the spread-

spectrum modulation.

00 = 0.7% (triangle), 0.7% (ZMFM, dither)

01 = 1.1% (triangle), 1.3% (ZMFM, dither)

10 = 2.3% (triangle), 2.6% (ZMFM, dither)

11 = 4.6% (triangle), 5.2% (ZMFM, dither)

3:2

FLL2_SS_FREQ

[1:0]

FLL2 Spread Spectrum Frequency

Controls the spread spectrum modulation

frequency in Triangle mode.

00 = 439kHz

01 = 878kHz

10 = 1.17MHz

11 = 1.76MHz

1:0

FLL2_SS_SEL

[1:0]

FLL2 Spread Spectrum Select

00 = Disabled

01 = Zero Mean Frequency (ZMFM)

10 = Triangle

11 = Dither

Table 109 FLL Spread Spectrum Control

WM8281ECS/R Datenblatt(PDF) 287 Page - Cirrus Logic

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