<div dir="ltr"> Well I have the low pass RLC filter into the OpAmp. I get less ripple at the higher PWM frequencies however at those frequencies I have much less granularity on the duty cycle. Trying to deal with the ripple. Guess I should look at different RLC filter values next. <br><div><br></div><div>The ADC input is on another board and I have no control over it. I need to supply a stable DC voltage to it. The current device (obsolete now) only deviates by 10 mV or less according to its raw ADC reads. I need to match that or the SW reading the ADC is not satisfied. My low pass filter attempt so far deviates at best by 50 mV. <br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Jun 29, 2020 at 11:57 PM Jon Wolfe <<a href="mailto:jonjwolfe@anibit.com">jonjwolfe@anibit.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<div dir="auto">
<div dir="auto">Yeah an rc low pass filter is the way to go. I've done it that way many times. The unity gain op amp could give you a buffer on the filter output, but I think ADCs are usually high impedance inputs. Depending on how fast you need the signal to change could impact what op amp you would need to use. You could play around in LT spice with different frequencies and component values to find something that works. Pete would know better than me, but I think the downside to higher frequency might be higher power draw, since more of the signal is going through the cap in the filter.</div><div dir="auto"><br></div>
<div id="gmail-m_6516571825788142142aqm-original" style="color:black">
<div dir="auto"><div style="color:black">
<p style="color:black;font-size:10pt;font-family:sans-serif;margin:8pt 0px">On June 29, 2020 10:32:55 PM Pete Soper via TriEmbed <<a href="mailto:triembed@triembed.org" target="_blank">triembed@triembed.org</a>> wrote:</p>
<blockquote type="cite" class="gmail_quote" style="margin:0px 0px 0px 0.75ex;border-left:1px solid rgb(128,128,128);padding-left:0.75ex">
The classic way to do this is with a low pass filter. If you google "PWM DAC" you'll find what you need. But the performance is going to be a function of the PWM frequency and how precisely you can change the duty cycle.<div dir="auto">Pete</div><div><br></div><div style="font-size:100%;color:rgb(0,0,0)" dir="auto"><div>-------- Original message --------</div><div>From: Charles A via TriEmbed <<a href="mailto:triembed@triembed.org" target="_blank">triembed@triembed.org</a>> </div><div>Date: 6/29/20 10:23 PM (GMT-05:00) </div><div>To: <a href="mailto:triembed@triembed.org" target="_blank">triembed@triembed.org</a> </div><div>Subject: [TriEmbed] PWM to Analog 0 to 5 VDC? </div><div><br></div></div><div dir="ltr">Anyone have a favorite circuit or chip to convert a PWM signal to a 0 to 5 VDC signal? The resulting voltage needs to be very stable. It feeds an ADC input. I've looked at an RL circuit into an OpAmp that also has a cap to ground at the OpAmp input. The DVM says it's stable but the ADC reading the voltage says it's not. I'm measuring 100 mV deviations. Would like to get to a 10 mV deviation. I've tried changing cap values on the input as well as adding caps on the output side of the OpAmp. Made improvements but still not good enough. So looking for suggestions please.<div><br></div><div>Thanks,</div><div>Chuck</div></div>
<div>_______________________________________________</div>
<div>Triangle, NC Embedded Computing mailing list</div>
<div><br></div>
<div>To post message: <a href="mailto:TriEmbed%40triembed.org" target="_blank">TriEmbed@triembed.org</a></div>
<div>List info: <a href="http://mail.triembed.org/mailman/listinfo/triembed_triembed.org" target="_blank">http://mail.triembed.org/mailman/listinfo/triembed_triembed.org</a></div>
<div>TriEmbed web site: <a href="http://TriEmbed.org" target="_blank">http://TriEmbed.org</a></div>
<div>To unsubscribe, click link and send a blank message: mailto:<a href="mailto:unsubscribe-TriEmbed%40bitser.net" target="_blank">unsubscribe-TriEmbed@bitser.net</a>?subject=unsubscribe</div>
<div><br></div>
<div><br></div></blockquote>
</div>
</div>
</div><div dir="auto"><br></div>
</div></div>
</blockquote></div>