Wolfson mono DAC and speaker amplifier

The WM9081 benefits from an integrated high efficiency 2.6W switchable class AB/D speaker amplifier, dynamic range controller and ReTune(tm) Mobile 5 band Parametric Equalizer. WM9081 achieves audio performance of 92dB SNR in Class D mode and 1 percent THD+N @ 2.4W output power into 4 ohm speaker loads. Compared to typical two chip solutions which use a DAC and separate class D amplifier the WM9081 consumes approximately 30 percent less PCB area and achieves an average 20 percent BOM cost reduction.

The WM9081 integrates a ReTune(tm) Mobile 5 band Parametric Equaliser with fully programmable coefficients allowing speaker frequency response compensation and music profiles to be defined by the end user. Programmable dynamic range control is integrated to help boost low-level signals to maximise volume for improved intelligibility. The WM9081 features a limiter designed to prevent audio signal clipping and distortion, which can overload the battery and potentially damage the speakers.

A digital audio interface gives the system designer several advantages in terms of noise immunity/reduction. Digital input allows the WM9081 to be located close to the speakers in multi-channel systems without the need for long analogue connections. By locating the driver close to the speaker the need for bulky and expensive class D filters is removed, whilst PCB track lengths, which carry noisy high frequency switching currents, can be minimised.

The WM9081's integrated register write sequencer helps to minimise software development time. A number of signal paths (such as DAC to speaker mode) can be enabled and disabled by just one register write. To do this, the internal sequencer initiates a sequence of pre programmed multiple writes independently within the WM9081, offloading control interface communication between the processor and WM9081.

David Brown, Audio Amps Product Line Manager, Wolfson Microelectronics comments: With the WM9081, designers of portable navigation devices and other similar systems do not need to sacrifice audio performance to maximise output power. Drawing on our audio expertise, Wolfson has developed a single-chip integrated device, which not only enables OEMs to make significant savings on PCB space and BOM cost, but also achieves a radically improved user experience by squeezing the absolute best, in terms of performance, intelligibility and noise immunity, from low cost speakers.

The WM9081 supports four control interface addresses and four-channel TDM to allow multiple devices to be configured and driven independently. Controlling the device is done via a standard 2-wire, 3-wire, or 4-wire control interface or by hardware control pins.