I'm building a circuit on a breadboard with a microcontroller and a DAC. My breadboard ground/Vcc planes are set up like this: (The numbers indicate which lines are wired together, the supply voltage and ground are connected to the top rows.)
1----------- Digital ground
2----------- Vcc
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1----------- Digital ground
2----------- Vcc
1----------3 Digital ground
2----------- Vcc
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-----------3 Analog ground
2----------- Vcc
The Vcc buses are wired together, as are the digital ground buses. The analog ground is connected to the digital ground in only one place.
However, I'm getting lots of noise on the digital ground (amplitude between 100 and 200 mV). The noise on the analog ground is not as intense, but when a certain pin changes state on the microcontroller there is a glitch that is very noticeable on the analog ground.
How can I reduce noise on the ground lines, and prevent the digital glitches from leaking into the analog portion of my circuit? I know breadboards have lots of parasitic capacitance and shouldn't even be used for high-frequency digital circuits, but it's the best I can do for now. I'm using a regulated DC power supply at 5V and the voltage is very clean; the microcontroller is likely responsible for all the noise.
I can post scope readings and a schematic soon.
1----------- Digital ground
2----------- Vcc
||||||||||||
||||||||||||
1----------- Digital ground
2----------- Vcc
1----------3 Digital ground
2----------- Vcc
||||||||||||
||||||||||||
-----------3 Analog ground
2----------- Vcc
The Vcc buses are wired together, as are the digital ground buses. The analog ground is connected to the digital ground in only one place.
However, I'm getting lots of noise on the digital ground (amplitude between 100 and 200 mV). The noise on the analog ground is not as intense, but when a certain pin changes state on the microcontroller there is a glitch that is very noticeable on the analog ground.
How can I reduce noise on the ground lines, and prevent the digital glitches from leaking into the analog portion of my circuit? I know breadboards have lots of parasitic capacitance and shouldn't even be used for high-frequency digital circuits, but it's the best I can do for now. I'm using a regulated DC power supply at 5V and the voltage is very clean; the microcontroller is likely responsible for all the noise.
I can post scope readings and a schematic soon.