8.3.2.4 Digital Clipper

A digital clipper is integrated in the oversampled domain to provide a component-free method to set the clip point of the speaker amplifier. Through the "Digital Clipper Level x" controls in the I²C control port, the point at which the oversampled digital path clips can be set directly, which in turns sets the 10% THD+N operating point of the amplifier. This is useful for applications in which a single system is designed for use in several end applications that have different power rating specifications. Its place in the oversampled domain ensures that the digital clipper is acoustically appealing and reduces or eliminates tones which would otherwise foldback into the audio band during clipping events. Figure 39 shows a block diagram of the digital clipper.

Figure 39. Digital Clipper Simplified Block Diagram

As mentioned previously, the audio signature of the amplifier when the digital clipper is active is very smooth, owing to its place in the signal chain. Figure 40 shows the typical behavior of the clipping events.

Figure 40. Digital Clipper Example Waveform for Various Settings of Digital Clip Level [19:0]

It is important to note that the actual signal developed across the speaker will be determined not only by the digital clipper, but also the analog gain of the amplifier. Depending on the analog gain settings and the PVDD level applied, clipping could occur as a result of the voltage swing that is determined by the gain being larger than the available PVDD supply rail. The gain structures are discussed in detail below for both Hardware Control Mode and Software Control Mode.