With LCD/OLED TVs, soundbars, and home theater audio-visual systems advancing towards high performance, low power consumption, and miniaturization, Richtek has introduced...RT9125Dual-channel digital input audio amplifier, providing a more flexible and efficient solution for audio systems.
RT9125Supports 30W dual-channel output, combined with Richtek's patented Common Mode Hopping (CMH) technology, effectively reducing power consumption at typical listening volumes (output power less than 5W). Additionally, it features a unique built-in Dynamic Range Compression (DRC) function, allowing independent adjustment of the left and right channels, making it suitable for multi-channel applications, effectively simplifying design and enhancing system flexibility.
RT9125It also supports a Class-D switching frequency of up to 768kHz, which effectively reduces the required inductance value for external low-pass filters, simplifying PCB layout design. When operating at a voltage below 15V, it can even achieve an inductance-free architecture, further reducing overall component costs. Combined with its low noise characteristics, it meets the comprehensive performance and size requirements of modern audio devices. This article will provide an in-depth introduction.RT9125Technical features and applications to help you create audio products that combine sound quality and efficiency.
1 Product Features
1.1 Patented CMH technology effectively reduces power consumption.
RT9125Adopting the patented Common Mode Hopping (CMH) technology from Leaptronix, it is specifically designed to enhance the efficiency of audio amplifiers under light load conditions. In most daily usage scenarios, audio devices often operate at lower output power levels (e.g., less than 5W). During these conditions, traditional BD architecture maintains a fixed 50% switching duty cycle, resulting in larger inductor current ripple, which increases system power consumption.
The core concept of CMH technology is to actively adjust the switching duty cycle under light load conditions, as shown in Figure 1.RT9125Dynamically adjust the originally fixed 50% duty cycle (red dashed line) in the BD architecture to approximately 25% (blue solid line) to effectively reduce the amplitude of the inductor current ripple.
According to the formula for inductor current ripple: Iripple = (Duty × PVDD) / (2 × fs × L)
It is clear that reducing the switch duty cycle can decrease the ripple current on the inductor, thereby reducing the average inductor current and overall power consumption. Figure 2 shows the actual efficiency measurement results, where the efficiency using CMH technology under light load conditions can reach up to 91%, saving approximately 3% of power consumption compared to traditional methods, significantly extending the battery life of powered products.
Figure 1. Comparison of BD and CMH inductance ripple
Figure 2. BD vs. CMH light load efficiency comparison chart
1.2 Independent DRC control, supports multi-channel speakers
RT9125Equipped with dynamic range compression (DRC) functionality that allows independent control of the left and right channels, it is specifically designed to meet the protection needs of dual-channel and multi-channel speaker systems. Traditional dual-channel amplifiers typically use a shared DRC setting to control both channels, making it difficult to provide precise protection tailored to speakers with different characteristics (such as tweeters and woofers). This also increases the complexity of PCB design.
RT9125Effectively addressed the aforementioned issues, allowing users to independently set DRC thresholds for the left and right channels. As shown in Figure 3, users can adjust different compression thresholds based on the specific requirements of the tweeter in the left channel and the woofer in the right channel, thereby significantly enhancing hardware protection and preventing speaker damage caused by distortion.
Furthermore, in the multi-channel application scenario as shown in Figure 4,RT9125It is also possible to independently optimize DRC settings for each channel speaker's characteristics, which not only enhances the flexibility of system design but also simplifies PCB routing and reduces electromagnetic interference (EMC) caused by complex wiring.
Figure 3. Diagram of stereo (tweeter and woofer) application
Figure 4. Diagram of multi-channel speaker application
1.3 Simplified design, complete protection
RT9125Under an 8Ω load, it supports a maximum output power of 2 × 30W. At PVDD = 12V / 8Ω and an output power of 2 × 10W, the conversion efficiency can reach up to 94%, as shown in Figure 5.RT9125It can operate stably without the need for additional external heat sinks, effectively reducing the manufacturing cost of the system.
Figure 5. Efficiency curve chart under 8Ω load
In terms of audio performance,RT9125Featuring an extremely low continuous output noise floor (35μV), it delivers pure and detailed sound quality. Even under low power output or light load conditions, it accurately reproduces sound details, ensuring a high-quality listening experience.
In terms of system design,RT9125Supports switching frequencies up to 768kHz, allowing the use of smaller filter components; when the operating voltage is below 15V, it also supports an inductor-less architecture, which helps simplify PCB layout and achieve a more compact system size.
Moreover,RT9125It also features a comprehensive system protection mechanism, including DC-blocking filtering, short-circuit detection, and over-temperature protection, to ensure the reliability and stability of the system under various operating conditions.
2 Application Examples
RT9125Supports up to 16 groups of independent I²C address settings, making it particularly suitable for multi-channel systems. This significantly reduces the need for multiple I²C control signals from the system-on-chip (SoC), effectively simplifying signal routing and interface design. Figure 6 illustrates this.RT9125A typical application diagram for a Soundbar multi-channel audio system; Figure 7 shows a reference application example of its use in an LCD/OLED TV multi-channel system. Through flexible multi-address settings,RT9125Can meet the needs of different channel configurations, enhancing the flexibility of system integration.
Figure 6. Example of Soundbar System Application
Figure 7. Example of a Multi-Channel System for LCD/OLED TVs
Source: Richtek Technology Corporation
►场景应用图
►展示板照片
►方案方块图
►核心技术优势
The RT9125 is a high-efficiency 2S input stereo channel audio power amplifier capable of delivering 2x30W to an 8Ω BTL speaker load. It offers over 94% power efficiency and does not require a heatsink. The built-in protection circuitry provides over-temperature, over-current, over-voltage, DC, and under-voltage protection while reporting error status. The RT9125 is an I2S device that receives all clocks from external sources. A fully programmable data path routes these channels to the internal speaker drivers. The RT9125 features three-band DRC and a flexible multi-band dual fourth-order setup for anti-clipping, power limiting, and speaker equalization. The recommended junction temperature range is -40°C to 150°C, and the ambient temperature range is -40°C to 85°C.
►方案规格
30W dual-channel audio amplifier