PWM DAC vs Delta-Sigma DAC

[bamboo]

pwm dac

Hello,
If anyone can explain what's the different between the PWM DAC and
Delta-Sigma DAC?
If they can be used in the same purpose of audio? They tell us PWM
DAC can use pure logic process and Delta-Sigma DAC need mixed signal
process .
Thanks in advance.

 

[chun_hung86]

delta sigma dac

do you design a PWM?

 

[eda4you]

delta-sigma dac

Both dacs need "mixed-signal" processes since the output stages need analog post processing!

while pwm vaires the pulse width of the output linearly to the digital input (V_out rms ~ V_in_digital) , a sigma-delta dac has a more complex signal processing. the quantization noise of the pwm dac is constant over the whole spectrum, while due to (sigma-delta) noise-shaping signal processing most of the quantization noise is shifted out of your signal bandwidth (oversampling required!). Therefore the SNR is better as for pwm for same power dissipation and convertion rates. another benefit over the pwm consists in good DNL and INL compared to the pwm dac.

in both cases, the output of the dacs are filtered (passive or active) afterwards in order to supress the "high frequency" noise.

 

[yeechyan]

dac pwm

For your information: **broken link removed**

Class D audio amplifiers implements PWM DAC at the output stage.

 

[okguy]

sigma delta pwm

But why can't you use class D with sigma-delta DAC :?:

 

[eda4you]

pwm vs dac

But why can't you use class D with sigma-delta DAC :?:

Maybe,because the baudrate shouldn't be to high? 1-bit sigma-delta needs OSR > min. 16 to make sense.