User manual

The Audio shut-down signal (AUD_SD) is used to mute the audio output. It is connected to
Zynq PL pin T17. To use the audio output, this signal must be driven to logic high.
The frequency response of SK Butterworth Low-Pass Filter is shown in Figure 13.2. The AC
analysis of the circuit is done using NI Multisim 12.0.
Figure 13.2. Audio Output Frequency Response.
13.1 Pulse-Width Modulation
A pulse-width modulated (PWM) signal is a chain of pulses at some fixed frequency, with each
pulse potentially having a different width. This digital signal can be passed through a simple
low-pass filter that integrates the digital waveform to produce an analog voltage proportional to
the average pulse-width over some interval (the interval is determined by the 3dB cut-off
frequency of the low-pass filter and the pulse frequency). For example, if the pulses are high for
an average of 10% of the available pulse period, then an integrator will produce an analog value
that is 10% of the Vdd voltage. Figure 13.1.1 shows a waveform represented as a PWM signal.
Figure 13.1.1. PWM Waveform.