In a bid to provide better sound quality and more output volume, mobile phone makers have been raising the internal voltage used to drive micro speakers – from 3.3V through to 5V, and recently as high as 8V. At this year’s Mobile World Congress 2013, NXP Semiconductors launches the new TFA9890 speaker driver IC, which can provide a 9.5V boost voltage from an integrated DC/DC converter. Increasing the voltage headroom in the audio driver IC prevents amplifier clipping and keeps sound quality high at maximum volume.
The most powerful driver yet for micro speakers, the TFA9890 safely drives a record 4W of peak power into a standard 8-ohm speaker that is typically rated at 0.5 W, making a clear improvement to the sound output and quality of mobiles, tablets, TVs and portable speakers.
“As handsets increasingly become multimedia devices, the message from consumers is loud and clear: Better sound quality can be the difference between a phone you tolerate and a phone you love,” said Shawn Scarlett, director of marketing, mobile audio solutions, NXP Semiconductors.
Whereas traditional approaches have required cutting bass frequencies to avoid damaging the speaker, the TFA9890 builds on the advanced speaker protection introduced in the TFA9887 to enable safe operation while working at near-peak output at all times. The fully integrated protection includes adaptive excursion control, a unique approach that compensates for real-world changes in the acoustic environment. The IC measures current and voltage to the speaker, and uses the information to adapt the protection algorithm to account for changes like ageing, damage to the enclosure, and blocked speaker ports.
The feedback-controlled excursion protection algorithm enables the TFA9890 – a single chip that includes NXP’s CoolFlux DSP, a Class-D amplifier with current sensing, and a DC-to-DC converter – to provide nearly twice as much power into 8-ohm speakers, with sound output typically 6-12 dB higher than the TFA9887. In addition to increasing the speaker volume, the DC-to-DC converter’s 9.5V boost voltage improves sound quality by increasing voltage headroom and eliminating amplifier clipping.
Other circuits and algorithms which improve sound quality include an advanced clip avoidance algorithm, which 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. Further, the intelligent DC-to-DC boost converter in the TFA9890 also prevents the audio system from causing battery under-voltage issues for the mobile device. The advanced, embedded algorithms require no separate licensing and allow designers to customise their audio sound quality and choose how to optimise the phone’s performance.