DAC output not working

danieloneill9 · ‎2012-09-04

Posted on September 05, 2012 at 04:38

Hi All,

I had the DAC working using DMA to out put a sinewave continuously and it seems to have stopped working when I tried to change which timer I triggered off. After changing the timer configuration back it still doesn't work.

I believe I configure everything I need to and I have code that read DAC->DOR1 out via the USART and it shows this data updating as I expect but I don't see any voltage on the DAC pin.

Any ideas?

Regards,

Daniel

#dac

frankmeyer9 · ‎2013-01-29

Posted on January 29, 2013 at 20:45

I remember a similiar thread, who got probably lost in this forum ...

I'm pretty sure you enabled the output buffer for the DAC.

Take a closer look at the datasheet. With this output buffer enabled, you have an offset voltage of up to 200mV at zero output. Not exactly rail-to-rail, but not so bad compared to other opamps.

megapin · ‎2013-01-30

Posted on January 30, 2013 at 19:49

output buffer is desabled (:

if enable then voltage is 200 mV

it's bad.

frankmeyer9 · ‎2013-01-31

Posted on January 31, 2013 at 10:27

How do you load the DAC ?

To cite from the datasheet (5.3.18, tbl 46):

When the buffer is OFF, the Minimum resistive load between DAC_OUT and VSS to have a 1% accuracy is 1.5 MOhm.

I guess you need a buffer stage, or need to increase the input impedance of the existing one.