ADC reading ripple dissapears when programmer connected to board

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Anonymous
Not applicable
        Hi, I have a prototype etched board. I have two PSoC 29466 which comunícate with each other and then one of them sends that two the computer over bluetooth. Both PSoC are Reading different ADC channels using a DualADC. So far everything Works fine but we have found a problema. The ADC readings are plotted in a graph in real time and we can see a ripple in the readings. It is about 50mv to 100 mV. We want to remove this undesired effect and we have found that when whe leave the MiniProg 1 programmer conected to the programming header of one of the PSoC, the ripple dissapears. The programmer isn't supplying power. The power comes from a 5V DC Wall adapter which then is converted to 3.3V through a regulator. Everything is working at 3.3V. Does anyone have any idea of what can be causing the ripple?   
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Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Looks really like a bad power-supply or a bad grounding. Check your supply voltage with a scope turned to AC and high gain to measure the ripple of the supply voltage. Check the capacitor between Vcc and GND for proper value.

   

 

   

Bob

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ETRO_SSN583
Level 9
Level 9
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If you look at the Miniprog1 PCB looks like a sizable C connected to

   

Vdd at the interface pin. So you are seeing additional C when it is

   

attached to your header.

   

 

   

If you have a DSO you can see what spectral components are present

   

and tackle source problems appropriately. Eg, is it 50/60 Hz or a ripple

   

produced by some switching element. Then filter appropriately.

   

 

   

Regards, Dana.

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Anonymous
Not applicable

 Hi,

   

Thanks to both. I thought so too. The problems is that I don't have the PCB here, and the tests is being made by another person that doesn't understand much about electronics so I will try to use a better cap for next revision, anyway at the end it will work with batteries so no worries 🙂

   

Thank you!

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