High Efficiency Class-D Audio Amplifier
Rev. 1 — 14 May 2019
Product data sheet
1 General description
The TFA9894D is a high efficiency 10 V boosted class-D audio amplifier with a
sophisticated SpeakerBoost and protection algorithm. It can deliver up to 5.6 W (AVG)
output power into an 8 Ω speaker and up to 6.2 W (AVG) output power into 4 Ω speaker,
at a battery supply voltage of 4.0 V. The internal adaptive DC-to-DC converter raises the
power supply voltage up to 10 V, providing ample headroom for major improvements in
A safe working environment is provided for the speaker under all operating conditions.
The TFA9894D maximizes acoustic output while ensuring membrane displacement
and voice coil temperature do not exceed their rated limits. This function is based on a
speaker box model that operates in all speaker environments (e.g. free air, closed box
or vented box). Furthermore, advanced signal processing ensures that the quality of
the audio signal is never degraded by unwanted clipping or distortion in the amplifier or
The adaptive sound maximizer algorithm uses feedback to calculate both the
temperature and the excursion accurately, allowing the TFA9894D to adapt to changes in
the acoustic environment.
Internal adaptive DC-to-DC conversion boosts the supply rail to provide additional
headroom and power output. The supply voltage is only raised when necessary. This
maximizes the output power of the class-D audio amplifier while limiting quiescent power
The device can be configured to drive either a hands-free speaker for audio playback,
or a receiver speaker, for handset playback, allowing it to be embedded in platforms
supporting both a hands-free speaker and a handset speaker. The maximum output
power, the gain, and the noise levels are lower in handset call use case than in hands-
free call use case.
The TFA9894D also incorporates battery protection. By limiting the supply current
when the battery voltage is low, it prevents the audio system from drawing excessive
load currents from the battery, which could cause a system undervoltage. This circuitry
minimizes the impact of a falling battery voltage by preventing unexpected device switch
off due to excessive current drawn from the battery.
The device features a second order closed loop architecture, used in a class-D audio
amplifier, providing excellent audio performance and high supply voltage ripple rejection.
The audio input interface is TDM and the control settings are communicated via an I2C-
The TFA9894D is available in a 48-bump wafer level chip-size package (WLCSP) with a
400 μm pitch.