This part is a kind of semiconductor called STA335BW.

Function of this product has 2.1 channels high efficiency digital audio system.

Manufacturers : STMicroelectronics

Image and pinout :

Some of the text within the PDF file :

STA335BW 2.1 channels high efficiency digital audio system Preliminary Data Features ■ ■ Wide supply voltage range (5 to 24V) 4 Power Output Configurations – 2 channels of ternary PWM (stereo mode) (2 x 20 W @ 8 Ω , 18 V) – 3 channels - left, right using binary and LFE using ternary PWM (2.1 mode) (2x10W + 1x20 W @ 2 x 4 Ω , 1 x 8 Ω, 20 V) – 1 channel PWM output (parallel-mode) (1 x 40 W) – 2 channels of ternary PWM (2 x 20 W) + stereo lineout ternary 2.1 Channels of 24-Bit DDX® >94dB SNR and Dynamic Range Selectable 32 KHz to 192 KHz Input Sample Rates I2C control with Selectable Device Address Digital Gain/Attenuation +48 dB to -80 dB in 0.5 dB steps Soft Volume Update Individual Channel and Master Gain/Attenuation Dual Independent Limiters/Compr [ ... ]

STA335BW PDF Datasheet Download