The WM8998 is a highly-integrated low-power audio hub codec for smartphones, tablets and other portable audio devices. It is optimised for the needs of multimedia devices using SLIMbus application processors.
The WM8998 digital core combines fixed-function signal processing blocks with a fully-flexible, all-digital audio mixing and routing engine, for extensive use-case flexibility. Signal processing blocks include filters, EQ, dynamics processors and sample rate converters.
A SLIMbus interface supports multi-channel audio paths and host control register access. Multiple sample rates are supported concurrently via the SLIMbus interface. Three further digital audio interfaces are provided, each supporting a wide range of standard audio sample rates and serial interface formats. Automatic sample rate detection enables seamless wideband/narrowband voice call handover.
The stereo headphone driver provides ground-referenced outputs, with noise levels as low as 1μVRMS for hi-fi quality line or headphone output. The codec also features a stereo line output, stereo 2W Class-D speaker outputs, a dedicated BTL earpiece output, PDM for external speaker amplifiers, and an IEC-60958-3 compatible S/PDIF transmitter. A signal generator for controlling haptics devices is included; vibe actuators can connect directly to the Class-D speaker output, or via an external driver on the PDM output interface. All inputs, outputs and system interfaces can function concurrently.
The WM8998 supports up to six analog mic/line inputs, and up to three PDM digital inputs. The input multiplexers support up to three signal paths. Microphone activity detection with interrupt is available. A smart accessory interface supports most standard 3.5mm accessories. Impedance sensing and measurement is provided for external accessory and push-button detection.
The WM8998 power, clocking and output driver architectures are all designed to maximise battery life in voice, music and standby modes. Low-power ‘Sleep’ is supported, with configurable wake-up events. The WM8998 is powered from a 1.8V external supply. A separate supply is required for the Class D speaker drivers (typically direct connection to 4.2V battery).
Two integrated FLLs provide support for a wide range of system clock frequencies. The WM8998 is configured using the I²C or SLIMbus interfaces. The fully-differential internal analog architecture, minimal analog signal paths and on-chip RF noise filters ensure a very high degree of noise immunity.