ESP32 Forum

Good day esteemed colleagues,

We are currently using the first gen ESP32 and we are utilizing the DAC
peripheral to adjust the Vout of a Buck Converter (TLV62569). The 8-bit
resolution was enough to allow us to adjust the Buck Converter's Vout from
1.10v to 3.60v. We did not require a high level of accuracy for the Vout,
but the Vout is monitored by the ADC peripheral and the DAC output
was adjusted when necessary.

We are planning to upgrade our current project to use the ESP32-S3 and we
are aware that it does not have a DAC peripheral in it's silicon. As much as
possible, we do not want to add an external DAC (via I2C or SPI) into our
design.

Upon reading this:
https://docs.espressif.com/projects/esp ... delta.html

It was suggested that using the Sigma-delta Modulation with a Sallen-Key Low Pass Filter
will allow us to have a "Pseudo DAC" output.

My question is, will this "Pseudo DAC" be enough to achieve similar effects
as what the 8-bit DAC achieved for the TLV62569 Buck Converter?

Our voltage requirements are the same, 1.10v to 3.60v Vout and the ADC peripheral
will monitor the Vout and adjust the Sigma-delta Modulation peripheral if necessary.

Best Regards,
Brad Roberts

That should work. Depending on the feedback loop speed required, you may even get away with a simple & stupid RC filter to smooth out the signal. Note that if you require more resolution than the 8-bit of that sigma-delta peripheral, the I2S device has a PDM mode that you could also abuse to get a sigma-delta signal.

There is nothing "pseudo" about a delta-sigma DAC; it is one of the m most widely used DAC implementations out there.

ESP_Sprite wrote: ↑

Sun May 29, 2022 1:23 am

That should work. Depending on the feedback loop speed required, you may even get away with a simple & stupid RC filter to smooth out the signal. Note that if you require more resolution than the 8-bit of that sigma-delta peripheral, the I2S device has a PDM mode that you could also abuse to get a sigma-delta signal.

I find the documentation of the I2S module used as PDM generator not very clear. Does it work in the same way as the GPIO PDM modulator? And then a 16 bit resolution can be achieved? I don't need it right now, but it may come in handy some time.