3W Stereo/6W Mono Class-D Audio Amplifier with I2C/PWM/Fixed Gain Volume Control

General Description

The ALC122 is a Stereo BTL or Mono PBTL Class-D audio amplifier that can drive speakers at a typical 4Ω in BTL mode or 2Ω in PBTL mode. Its maximum output power is up to Stereo BTL 3W at 5V power supply or Mono PBTL 6W at 5V power supplied when PBTL=H.

The ALC122 provides three volume control mechanisms; 64 steps I2C Volume Control, 64 steps PWM Duty Volume Control, and 4-Steps Fixed gain Volume Control.

PWM Duty Volume Control is patented by Realtek and useful for volume control in LCD monitor systems. With Realtek proprietary Class-D amplifier technology, the ALC122 offers good audio quality, high power-efficiency, requires fewer external components, and supports analog input.

The ALC122 can output power directly to the speaker with less power dissipation inside the silicon. This high efficiency with less run-time power consumption can greatly extend the battery life of portable consumer electronic devices and notebook PCs.


  • Stereo single-ended analog inputs
  • Output Power
    • Stereo BTL Po = 3W/CH at 4Ω load and 5V power with 10% THD+N ratio
    • Stereo BTL Po = 3W/CH at 4Ω load and 5V power with 10% THD+N ratio
  • Filter-less design for output
  • 64-steps PWM Duty Volume Control and range is from 30dB to -24dB monotonic steps
  • 64-steps I2C Volume Control with range from 30dB to -24dB monotonic steps
  • 4-steps Fixed Gain Volume Control (11dB /14dB /19dB /24dB)
  • Volume control types: I2C, PWM Input, and Fixed gain control
  • Pop noise suppression during Power Up/Down and Mute/Un-mute
  • Over-Current Protection (OCP) and short-circuit protection
  • Auto-recovery function to help sound recovery from OCP
  • Zero cross detection with soft volume function
  • External pin control for Shut Down mode
  • Speaker amplifier power supplies from 3V to 5.25V
  • 24-pin QFN4x4 Package


  • Notebook PCs
  • Portable Navigation Device/DVD Player/Games
  • All-in-One PC
  • Monitor, TV
  • Digital Photo Frame
  • USB Speaker