Author Topic: MCP4725, CLK ripple at output  (Read 740 times)

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Offline Jan80Topic starter

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  • Country: au
MCP4725, CLK ripple at output
« on: March 02, 2019, 03:52:41 am »
Hi, I'm considering usage of popular MCP4725 for a project, but I'm facing an issue which I couldn't find described anywhere on forums.
It appears that CLK signal of the microprocessor causes a ripple at the output of the DAC.
I already tried basic stuff like blocking caps, various runs of GND, different values of I2C pull-ups, different Arduino boards, different power supplies, but without affect on the DAC output.
My test setup consists of MCP4725 breakout board, arduino nano supplied of 12V battery pack(Vin) for the lowest possible noise. DAC uses 5V of arduino linear regulator. 
Top picture shows the output signal while alternating DAC by 1bit in the middle of the output range. 1bit represents cca 1.2mV and the pp-ripple is about 30mV which is way too high to accept.
Middle picture shows Vcc of DAC and the output. As you can see there is just very little noise at Vcc, nothing what would explain the issue. 
Bottom picture shows correlation of i2C CLK  and output signals.

Can anyone confirm my findings? Any idea how to get rid of the ripple or is this a feature of MCP4725 ( can't tell if it's genuine). thanks




 


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