WM8281ECSSLASHR datasheet(96/392 Pages) CIRRUS

96 / 392 page

WM8281

Rev 4.0

NOISE GENERATOR

The WM8281 incorporates a white noise generator, which can be routed within the digital core. The

main purpose of the noise generator is to provide ‘comfort noise’ in cases where silence (digital mute)

is not desirable.

Noise Generator (0Dh)

White Noise

Generator

NOISE_GEN_ENA

NOISE_GEN_GAIN

NOISE_GEN_RATE

Figure 35 Digital Core Noise Generator

The noise generator can be selected as input to any of the digital mixers or signal processing

functions within the WM8281 digital core. The bracketed number (0Dh) in Figure 35 indicates the

corresponding *_SRCn register setting for selection of the noise generator as an input to another

digital core function.

The sample rate for the noise generator is configured using the NOISE_GEN_RATE register - see

Table 23. Note that sample rate conversion is required when routing the noise generator output to any

signal chain that is asynchronous and/or configured for a different sample rate.

The noise generator is enabled using the NOISE_GEN_ENA register bit as described in Table 20.

The signal level is configured using NOISE_GEN_GAIN.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R112

(0070h)

Comfort

Noise

Generator

NOISE_GEN_EN

Noise Generator Enable

0 = Disabled

1 = Enabled

4:0

NOISE_GEN_GA

IN [4:0]

00h

Noise Generator Signal Level

00h = -114dBFS

01h = -108dBFS

02h = -102dBFS

…(6dB steps)

11h = -6dBFS

12h = 0dBFS

All other codes are Reserved

Table 20 Noise Generator Control

HAPTIC SIGNAL GENERATOR

The WM8281 incorporates a signal generator for use with haptic devices (eg. mechanical vibration

actuators). The haptic signal generator is compatible with both Eccentric Rotating Mass (ERM) and

Linear Resonant Actuator (LRA) haptic devices.

The haptic signal generator is highly configurable, and includes the capability to execute a

programmable event profile comprising three distinct operating phases.

The resonant frequency of the haptic signal output (for LRA devices) is selectable, providing support

for many different actuator components.

The haptic signal generator is a digital signal generator which is incorporated within the digital core of

the WM8281. The haptic signal may be routed, via one of the digital core output mixers, to a Class D

speaker output for connection to the external haptic device, as illustrated in Figure 36. (Note that the

digital PDM output paths may also be used for haptic signal output.)

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