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NXP Release New Sound Chip for Mobile Micro Speakers

TFA9890 audio driver IC pumps out a record 4 W of peak power into a standard 8-ohm speaker

In a push for better sound quality and more output volume, leading 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. NXP have now released the new TFA9890 speaker driver IC, which enables an unprecedented 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 4 W 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.

TFA9890 High Performance Audio Amplifier IC

“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. “The commercial success of the TFA9887 audio IC we introduced last year has been game-changing - and with the TFA9890, we're raising the bar for sound quality from mobile devices.”

Advanced speaker protection for outstanding sound quality
Whereas traditional approaches have required cutting bass frequencies to avoid damaging the speaker, the TFA9890 builds on the advanced speaker protection introduced in the award-winning 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.

TFA9890 High Performance Audio Amplifier IC

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 customize their audio sound quality and choose how to optimize the phone's performance.

Features of the TFA9890 Audio Driver IC

  • Sophisticated speaker-boost and protection algorithm that maximizes speaker performance while protecting the speaker:
    • Fully embedded software, no additional license fee or porting required
    • Total integrated solution that includes DSP, amplifier, DC-to-DC, sensing and more
  • Adaptive excursion control - guarantees that the speaker membrane excursion never exceeds its rated limit
  • Real-time temperature protection - direct measurement ensures that voice coil temperature never exceeds its rated limit
  • Environmentally aware - automatically adapts speaker parameters to acoustic and thermal changes including compensation for speaker-box leakage
  • Speaker error detection (detects faulty speakers and enclosures)
  • Output power: 3.6 W (RMS) into 8 Ω at 3.6 V supply voltage (THD = 1 %)
  • Clip avoidance - DSP algorithm prevents clipping even with sagging supply voltage
  • Bandwidth extension option to increase low frequency response
  • Compatible with standard Acoustic Echo Cancellers (AECs)
  • High efficiency and low power dissipation
  • Wide supply voltage range (fully operational from 2.7 V to 5.5 V)
  • Two I²S inputs to support two audio sources
  • I²C-bus control interface (400 kHz)
  • Dedicated speech mode with speech activity detector
  • Speaker current and voltage monitoring (via the I²S-bus) for Acoustic Echo Cancellation (AEC) at the host
  • Fully short-circuit proof across the load and to the supply lines
  • Sample frequencies from 8 kHz to 48 kHz supported
  • 3 bit clock/word select ratios supported (32x, 48x, 64x)
  • Option to route I²S input direct to I²S output to allow a second I²S output slave device to be used in combination with the TFA9890A
  • TDM interface supported (with limited functionality)
  • Volume control
  • Low RF susceptibility
  • Input clock jitter insensitive interface
  • Thermally protected
  • 15 kV system-level ESD protection without external components
  • ‘Pop noise' free at all mode transitions

The NXP website address is www.nxp.com
[Reprinted with kind permission from NXP]