LPCXpresso LPC1769 board: why DAC is so noisy?

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by giusloq on Tue May 19 08:46:11 MST 2015
I'm using LPC1769 development board (OM13000) without a base board. I'm trying to use the DAC peripheral, but I have a problem.

When I set a 0 value, no problem. When I set 0x3FF (max value), the output value changes accordingly, but I see a noise signal with a scope. It seems it has bursts at about 20ms with a peak-to-peak level about 40mV.

I noticed the same noise signal is present on 3.3V rail too. I'm supplying the board through USB.

Is it normal? I'd like to use DAC for audio signal and this type of noise will be audible on the speaker.

I tried to change the clock divisor and DMA timeout for DAC peripheral, but the noise is the same.