TAS5825 is a closed loop class-D audio amplifier with 38 watt stereo output. Here are two parameters which show the excellent audio performance. The first one is idle channel noise, which is lower than 35 microwatts, which means at least the 110 dB signal noise reach you. 

And the second one is lower than 20 milliampere quiescent current at 12 watt PVDD. Regarding audio processing, TAS5825 has a 128 micro [INAUDIBLE] DSP core to provide powerful processing capability. And it can support true 192 kilohertz processing and optional smart amplifier algorithm for speaker protection. What's more, it also has sub-channel digital output for echo cancellation. TI also provides easy to use PPC graphical user interface for parameter tuning. 

Let's start with the first [INAUDIBLE] feature for longer battery lifetime, hybrid modulation. In order to compare the efficiency between traditional BD mode and hybrid mode, both PVDD and DVDD current are measured at the same condition of playing music. So orange color shows the PVDD current with BD mode. Otherwise, the blue one is for hybrid mode. It's obvious that PVDD power consumption on hybrid mode is less than BD mode. 

Based on time integration of current data, for 12 watt PVDD, the loss of hybrid modulation is 11.5 ampere second, and BD mode is 18.8 ampere second, which means almost a 39% saving. And for 3.3 watt DVDD, the loss of hybrid modulation is 8.1 watt ampere second. BD mode is 17.7 ampere second, which means almost 54% saving. 

If only considering audio amplifier PVDD and DVDD power consumption, hybrid modulation will make [INAUDIBLE] speaker battery life 1.72 times longer than traditional BD modulation. It's a great improvement for power saving. So here comes the question, how hybrid modulation significantly reduces power use? 

We need to begin with which power loss is happening when playing music. The first part is amplifier internal MOSFET switching loss. Normally this loss is related to RDSon, which means [INAUDIBLE] resistant to MOSFET in the PWM switching frequency. What's more, the internal switching loss goes higher along with bigger RDSon or higher PWM switching frequency. 

The second part is internal inductor loss. Based on empirical formula, the peak output of inductor [INAUDIBLE] current [INAUDIBLE] is positively correlated with PWM switching duty cycle, but negatively correlated with PWM switching frequency and inductance. And for switching through the cycle, this lower right corner figure shows blue curve with higher duty cycle and red curve with lower duty cycle. We can see higher duty cycle will make the peak output of inductance ripple current much bigger, which normally [INAUDIBLE] for a big internal inductor power loss. 

Our target is to get higher efficiency, which means lower power loss. Here are some methods to reduce loss based on previous analyses. From the perspective of internal switching loss, we needed to make RDSon smaller. However, it always means bigger die size and more expensive, so it's not the best choice. We can also reduce PWM switching frequency for smaller internal switching loss. But does it mean we can get a higher efficiency? Let's leave this question and talk more details later. 

Another point is to reduce internal inductor loss. The first method is to use a bigger inductor, which also means bigger PCB size and more expensive. So we do not consider it temporarily. The second choice is asking us to increase PWM switching frequency. Here is the same question, does higher PWM switching frequency mean higher efficiency? The answer is, not sure, because higher PWM switching frequency also means bigger internal switching loss. 

Based on different LC filter configurations, it's hard to decide whether increase or decrease switching frequency can get higher efficiency. So till now, we just have one remaining option, which is to reduce positive and negative [INAUDIBLE] switching to the cycle. 

So can we just simply reduce the common switching to the cycle for higher efficiency? The answer is, not exactly. Traditional BD modulation is using fixed 50% common duty, which means lower efficiency, but better THD performance due to always differential BD output. What [INAUDIBLE] modulation is trying to improve with efficiency by changing the common duty cycle to fix the 15%. But the drawback is worse THD performance, because the output [INAUDIBLE] will be single switching with big output power. 

Hybrid modulation can implement better THD performance and higher efficiency. What it does is to dynamically maintain differential switching output status with several common duty options. Except for more efficient, benefit, hybrid modulation can also maintain qualitative performance which is almost the same as BD modulation. As the right figure shows, the cyan stands for hybrid mode THD plus noise performance versus output power, which is almost the same as current BD mode, and much better than magenta [INAUDIBLE] mode. 

What's more, due to the noise of the common duty cycle with idle status, the hybrid mode idle current is also smaller than BD mode, and even [INAUDIBLE] mode. Now, based on detailed theoretical explanation of hybrid modulation, we can easily understand how it implements these three benefits.