WM8998 datasheet(37/307 Pages) WOLFSON

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WM8998

PD, October 2014, Rev 4.0

DEVICE DESCRIPTION

INTRODUCTION

The WM8998 is a highly integrated low-power audio hub CODEC for mobile telephony and portable

devices. It provides flexible, high-performance audio interfacing for handheld devices in a small and

cost-effective package. It is optimised for the needs of tablet devices and multimedia phones using

SLIMbus application processors.

The WM8998 digital core provides configurable capability for signal processing algorithms, including

parametric equalisation (EQ) and dynamic range control (DRC). Highly flexible digital mixing,

including stereo full-duplex asynchronous sample rate conversion, provides use-case flexibility across

a broad range of system architectures. A signal generator for controlling haptics vibe actuators is

included.

The WM8998 provides multiple digital audio interfaces, including SLIMbus, in order to provide

independent and fully asynchronous connections to different processors (eg. application processor,

baseband processor and wireless transceiver).

A flexible clocking arrangement supports a wide variety of external clock references, including

clocking derived from the digital audio interface. Two integrated Frequency Locked Loop (FLL) circuits

provide additional flexibility.

Unused circuitry can be disabled under software control, in order to save power; low leakage currents

enable extended standby/off time in portable battery-powered applications. Configurable ‘Wake-Up’

actions can be associated with the low-power standby (Sleep) mode.

Versatile GPIO functionality is provided, and support for external accessory / push-button detection

inputs. Comprehensive Interrupt (IRQ) logic and status readback are also provided.

HI-FI AUDIO CODEC

The WM8998 is a high-performance low-power audio CODEC which uses a simple analogue

architecture. Input path multiplexers select from up to 6 analogue mic/line and 3 digital microphone

inputs; combinations of up to 3 inputs can be supported. 7 DACs are incorporated, providing a

dedicated DAC for each output channel.

The analogue outputs comprise a 28mW (122dB SNR) stereo headphone amplifier with ground-

referenced output, a flexible (single-ended or differential) line output, a 100mW differential (BTL)

earpiece driver, and a Class D stereo speaker driver capable of delivering 2W per channel into a 4Ω

load. Six analogue inputs are provided, each supporting single-ended or differential input modes. In

differential mode, the input path SNR is 96dB. Up to 3 analogue or digital input paths can be

supported at one time.

The audio CODEC is controlled directly via register access. The simple analogue architecture,

combined with the integrated tone generator, enables simple device configuration and testing,

minimising debug time and reducing software effort.

The WM8998 output drivers are designed to support as many different system architectures as

possible. Each output has a dedicated DAC which allows mixing, equalisation, filtering, gain and other

audio processing to be configured independently for each channel. This allows each signal path to be

individually tailored for the load characteristics. All outputs have integrated pop and click suppression

features.

The headphone, line and earpiece output drivers are ground-referenced, powered from an integrated

charge pump, enabling high quality, power efficient headphone playback without any requirement for

DC blocking capacitors. Ground loop feedback is incorporated, providing rejection of noise on the

ground connections.

The Class D speaker drivers deliver excellent power efficiency. High PSRR, low leakage and

optimised supply voltage ranges enable powering from switching regulators or directly from the

battery. Battery current consumption is minimised across a wide variety of voice communication and

multimedia playback use cases.

The WM8998 is cost-optimised for a wide range of mobile phone applications, and features two

channels of Class D power amplification. For applications requiring more than two channels of power

amplification (or when using the integrated Class D path to drive a haptics actuator), the PDM output

channels can be used to drive two external PDM-input speaker drivers. In applications where stereo

loudspeakers are physically widely separated, the PDM outputs can ease layout and EMC by avoiding

the need to run the Class-D speaker outputs over long distances and interconnects.

WM8998 Datasheet(PDF) 37 Page - Wolfson Microelectronics plc

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