mrblueblue1234
Junior Member level 1
All,
I have an application where I will be receiving in a ground reference and two other analog signals that I am calling “Analog Ground and Signals” in the images below (left and green.) One of the pins of this connector goes directly to my analog ground reference plane (AGND).
Next I have a digital potentiometer that will take one of these analog signals, route through the potentiometer to the analog ground plane (AGND).
So far so good….
But since I want to use this digitally controlled potentiometer I will be connecting to a microcontroller that will send commands via I2C.
At this point I have introduced a second ground reference that I am calling digital ground (DGND). This will be the ground for my LDO regulator providing 3.3V and a ground for the microcontroller.
1.) At this point I was not 100% sure what to do with these ground references. Should I split these planes and connect at one point or just have one plane but keep things separated in distance? I have read different things on the web but I still was not 100% sure.
2.) What would be a recommend stackup for something like this? Two layer? Ground on the bottom and routing on the top? Then flood the top with ground?
3.) Then I was not sure which ground I should be referencing for the power supply return reference of the digital potentiometer. Should this be the digital or analog ground?
4.) Digital POT datasheet and layout recommendation:
MCP4651T-503E/ST
https://ww1.microchip.com/downloads/en/DeviceDoc/22096b.pdf
From the datasheet:
“The power source supplying these devices should be as clean as possible. If the application circuit has separate digital and analog power supplies, VDD and VSS should reside on the analog plane.”
Maybe for the digital potentiometer I should create a separate analog 3.3V (A3.3V) that powers up the potentiometers?
Thanks!
I have an application where I will be receiving in a ground reference and two other analog signals that I am calling “Analog Ground and Signals” in the images below (left and green.) One of the pins of this connector goes directly to my analog ground reference plane (AGND).
Next I have a digital potentiometer that will take one of these analog signals, route through the potentiometer to the analog ground plane (AGND).
So far so good….
But since I want to use this digitally controlled potentiometer I will be connecting to a microcontroller that will send commands via I2C.
At this point I have introduced a second ground reference that I am calling digital ground (DGND). This will be the ground for my LDO regulator providing 3.3V and a ground for the microcontroller.
1.) At this point I was not 100% sure what to do with these ground references. Should I split these planes and connect at one point or just have one plane but keep things separated in distance? I have read different things on the web but I still was not 100% sure.
2.) What would be a recommend stackup for something like this? Two layer? Ground on the bottom and routing on the top? Then flood the top with ground?
3.) Then I was not sure which ground I should be referencing for the power supply return reference of the digital potentiometer. Should this be the digital or analog ground?
4.) Digital POT datasheet and layout recommendation:
MCP4651T-503E/ST
https://ww1.microchip.com/downloads/en/DeviceDoc/22096b.pdf
From the datasheet:
“The power source supplying these devices should be as clean as possible. If the application circuit has separate digital and analog power supplies, VDD and VSS should reside on the analog plane.”
Maybe for the digital potentiometer I should create a separate analog 3.3V (A3.3V) that powers up the potentiometers?
Thanks!