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Audio Amplifier

TFA9871: 8.5V Highly Power-Efficient Class-D Audio Amplifier


The TFA9871 is a high-efficiency 8.5 V boosted Class-D audio amplifier. It can deliver up to 8 W peak output power into an 8 Ω speaker and up to 10 W peak output power into a 6 Ω speaker, at a supply voltage of 4.0 V. The internal adaptive DC-to-DC converter raises the supply voltage up to 8.5 V, providing ample headroom for major improvements in sound quality.

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 consumption.

The TFA9871 also comes with battery protection feature. 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 might harm a system under low voltage.

The TFA9871 is available in a 36-bump WLCSP (Wafer Level Chip-Size Package) with a 400 μm pitch.


  • High output power: 4.1 W (average) into 8 Ω at 4.0 V supply voltage (THD = 1%)

  • Supports handset (16 Ω or 32 Ω) and hands-free (4 Ω to 8 Ω) speaker configurations

  • High-efficiency, low power dissipation and low-noise speaker driver

  • Adaptive DC-to-DC converter increases the supply voltage smoothly while switching between Fixed Boost and Adaptive Boost modes, preventing large battery supply spikes and limiting quiescent power consumption

  • Wide supply voltage range (fully operational from 2.7 V to 5.5 V)

  • Very low noise output voltage<15 μV with -60 dBFS input at fs = 48 kHz)

  • Low battery current consumption<118 mA (Po = 380 mW, average music power)

  • I2C-bus control interface (400 kHz)

  • Speaker current and voltage monitoring (via the TDM-bus) for Acoustic Echo Cancellation (AEC) at the host

  • 16 kHz/32 kHz/44.1 kHz/48 kHz sample frequencies supported

  • Ultrasonic support via TDM running at 96 kHz

  • Programmable interrupt control via a dedicated interrupt pin

  • Low RF susceptibility

  • Thermal foldback and overtemperature protection

  • 15 kV system-level ESD protection without external components on amplifier output

System Block Diagram

Application Block Diagram


  • TFA9871 SDS

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