Similar to Δ Σ ADC, there is a type of DAC that also uses delta-sigma technology to improve conversion accuracy. Generally speaking, most audio DACs will use ΔΣ technology to improve the quality of audio output. As shown in the figure below, it is a block diagram of the internal module of the 24-bit oversampling audio DA converter PCM175x.
The ΔΣ DAC internally includes an interpolation filter and a ΔΣ modulator (modules including a digital integrator, a quantizer, and a feedback loop), a switched capacitor DAC, and an analog low-pass filter. Its key module is a Δ modulator, and its basic working principle is similar to that of a Δ Σ ADC. At its heart is a delta modulator, see the figure below. The input signal X1 is modulated into X2 through the Δ modulator. Inside the modulator, the input signal is first integrated. When the integrated value is greater than the input signal X1, the output of X2 is positive, otherwise, the output of X2 is negative. After such adjustments, we can find that the result of integrating X2 is X3. For the X2 signal, it is converted into an analog signal by a 1-bit switched capacitor DAC, and the analog signal corresponding to the original digital input signal can be restored by integration, and then the high-frequency noise is filtered out by low-pass filtering, and the signal is smoothed to obtain a high precision analog output signal. In an actual DAC, the following integration work will be moved to the beginning of the signal, that is, before X1. Doing so avoids the corresponding delay of the delta modulator to a rapidly changing input signal, as well as its inability to respond to DC.
