The device comes with a combination of safety features that include adaptive excursion control and real-time temperature protection, the TFA9887 monitors speakers through a current-sensing amplifier and enables safe operation while working at near peak output at all times.
“Poor mobile sound quality is often taken for granted. As speakers have become smaller, the quiet, tinny sound we’ve come to associate with mobile devices has got even worse,” said Shawn Scarlett, director of marketing, mobile audio product line, NXP Semiconductors. “Our new audio system looks to transform the listening experience, enabling louder, richer sound quality from virtually any mobile device. Consumers, handset makers and operators will immediately hear the difference.”
Speaker makers have to balance good sound, small size and reliability. As micro speakers have shrunk, designers have been forced to limit output power and sound quality. Amplifiers could easily deliver enough power to destroy the speaker at one frequency, while under-powering it at others. Until now, it has been impossible for system designers to know for sure when it was safe to apply extra power. The rule has therefore been to cut out bass frequencies and limit output power to avoid blowing the speaker – a common cause of failures in mobiles.
By incorporating circuits that monitor speaker performance and prevent damage, the NXP TFA9887 IC allows designers to break this rule. Adaptive excursion control measures the actual excursion of the speaker membrane to ensure that it never exceeds its rated limit. Real-time temperature protection measures the voice-coil temperature directly to prevent thermal damage.
Because the speaker is fully protected, the system can deliver significant levels of extra power to make the sound louder and better than before. The TFA9887 optimises the audio signal based on the movement of the speaker, using the full capabilities of the speaker without pushing beyond the limits.
An advanced clip avoidance algorithm monitors audio performance and prevents clipping, even when the power supply begins to sag. Bandwidth extension increases the low frequency response well below speaker resonance. And an intelligent DC-to-DC boost converter maximises audio headroom from any supply level despite battery under-voltage.
The TFA9887 automatically adapts to any changes in the speaker – including ageing, damage to the enclosure, and blocked speaker ports – helping to optimise performance and maintain the desired sound quality.
The entire system is integrated into a single chip with digital interfaces for portable devices. The IC incorporates NXP’s CoolFlux audio DSP, a high-efficiency class-D amplifier with current sensing, and a DC-to-DC boost converter. The advanced, embedded algorithms require no separate licensing. Additional tools allow designers to customize audio sound quality and choose how to optimize mobile device performance.