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Most controller/processor come with PWM output and integrated standalone DAC module....

My need is to generate 50/60Hz analog signal for testing purpose! Which would be the good choice PWM DAC or Standalone DAC?

Better in terms of: * Simple electronics * Simple coding * Quality signals (lesser distortion) * Sine wave generation

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    \$\begingroup\$ What do you define as "better"? Not all DACs are the same. Many high performance "standalone" sigma-delta DACs actually generate a (sort of) PWM signal. Also a 50/60Hz analog signal means little, a 50 Hz signal can have very different requirements depending on shape of the signal and its bandwidth. \$\endgroup\$ Commented Feb 18, 2019 at 11:05
  • \$\begingroup\$ Sine or square wave? \$\endgroup\$
    – winny
    Commented Feb 18, 2019 at 11:07
  • \$\begingroup\$ Better in terms of: * Simple electronics * Simple coding * Quality signals * Sine wave generation \$\endgroup\$ Commented Feb 18, 2019 at 11:08
  • \$\begingroup\$ Do you only care about generating pure sine tones, or more complicated waveforms should be supported? \$\endgroup\$
    – anrieff
    Commented Feb 18, 2019 at 12:29

2 Answers 2

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Given the MCU_PWM_DAC has electro-static-discharge protection diodes on the (inputs and) outputs of the MCU, your signal will always have MCU_CLOCK and MCU_program_related spikes and trash that are non-random.

Use this filter on the "DAC"

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ I like this approach. If parts allow, the filter corner can be made a little sharper (less overdamped) by keeping the RC of each section constant. In principle for this example 1k/10u , 3k3/3u3 , 10k/1u ... this is prob more reasonable with higher freq filter (a bit smaller caps) \$\endgroup\$
    – Pete W
    Commented Feb 13, 2021 at 18:33
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I'm assuming that a Sinewave output is required here.

Any primitive DAC you implement will work fine but will likely be noisy unless a fair bit of design is carried out to filter it etc.

All things considered the PWM DAC you implement yourself is likely to be much noisier than a standalone one - purely for the reason that it has been optimized for a particular usage / price point. On the other hand a PWM one will likely be cheaper and easier to get working - because you will not need to figure out the comms and configuration registers of the external DAC.

So for simple I would go with the PWM option - but for better quality I would use the external DAC.

Actually if it's just the signal that is of interest, I would just use a computer with sound card to generate the signals if that is an option. You should get a very clean signal at these frequencies with 16-24bits of resolution.

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