This post explains for the Audio Power Amplifier.
The Part Number is RT9108NB.
The function of this semiconductor is 15W Stereo Class-D Audio Power Amplifier.
The package is TSSOP 28 Pin type
Preview images :
The RT9108NB is a 15W per channel, high efficiency Class D stereo audio amplifier for driving Bridge Tied Load (BTL) speakers. The RT9108NB can drive stereo speakers with load as low as 4Ω. Its high efficiency eliminates the need for an extra heat sink when playing music. The gain of the amplifier can be controlled by two gain select pins. The outputs are fully protected against shorts to GND, PVCC, and output to output with an auto recovery feature and monitored output […]
1. 8V to 26V Input Supply Range
2. 6W/CH for an 8Ω Load, 10V Supply at 10% THD +N
3. 90% Efficiency Eliminates Need for Heat Sinks
4. Four Selectable or Fixed Gain Settings
5. Mute Function Amplifier
6. Robust Pin- to-Pin Short Circuit Protection
7. Thermal Protection with Auto Recovery Option
8. Speaker Protection with Adjustable Power Limit