BrianSw
Newbie level 3
This has always been a confusing factor for me in designing some circuits.
I am not sure what I should be connecting to my analog ground plane.
I can't put the schematic on here right now but I can describe the circuits involved. It starts with a (Analog Devices AD8211) current shunt amplifier connected to a resistor for measuring current at the high side. The output of this is then sent to a PGA (Microchip MCP6S22) with the gain and channel selected using SPI control by a Pic processor. Output of PGA is sent to an Active LowPass Filter using a single opamp. Output of the lowpass filter is then connected to a (Linear Technology LT1860) AD converter. Measurement data then is sent to PIC via SPI bus. Connected to the LT1860 is a (linear Technology LT1021) 5 V reference.
What I already have connected to my analog ground plane is the A/D converter Analog and Digital grounds as well as the supply, and voltage reference input bypass caps as per the data sheet. Think I good here.
I have also connected the lowpass filter grounds to the analog ground plane. It is a single opamp configured as a Sallen-Key filter. This includes the opamp bypass cap also. It is a single supply opamp not split. Probably good here too I think.
Questionable is the PGA and the Current shunt amplifier.
Not sure what to do with the PGA as it is both a Digital and Analog device that shares a common ground. Should this be connected to the Digital or Analog ground plane? And what to tie the supply bypass caps to?
Next in line is the Current shunt amplifier. Not a digitally controlled device so is it safe to assume I can tie this to the Analog Plane as well as it's supply bypass cap?
These circuits are part of a much larger design and will be mounted on a multilayer PCB board with seperate planes for power +5v, + 28, analog ground, digital grounds.
I'm not an electronics engineer. I'm electronics technician where I work doing some engineering design work. I have a pretty good electronics background just not alot of board layout designs.
Help is always greatly appreciated.
Thanks,
Brian
I am not sure what I should be connecting to my analog ground plane.
I can't put the schematic on here right now but I can describe the circuits involved. It starts with a (Analog Devices AD8211) current shunt amplifier connected to a resistor for measuring current at the high side. The output of this is then sent to a PGA (Microchip MCP6S22) with the gain and channel selected using SPI control by a Pic processor. Output of PGA is sent to an Active LowPass Filter using a single opamp. Output of the lowpass filter is then connected to a (Linear Technology LT1860) AD converter. Measurement data then is sent to PIC via SPI bus. Connected to the LT1860 is a (linear Technology LT1021) 5 V reference.
What I already have connected to my analog ground plane is the A/D converter Analog and Digital grounds as well as the supply, and voltage reference input bypass caps as per the data sheet. Think I good here.
I have also connected the lowpass filter grounds to the analog ground plane. It is a single opamp configured as a Sallen-Key filter. This includes the opamp bypass cap also. It is a single supply opamp not split. Probably good here too I think.
Questionable is the PGA and the Current shunt amplifier.
Not sure what to do with the PGA as it is both a Digital and Analog device that shares a common ground. Should this be connected to the Digital or Analog ground plane? And what to tie the supply bypass caps to?
Next in line is the Current shunt amplifier. Not a digitally controlled device so is it safe to assume I can tie this to the Analog Plane as well as it's supply bypass cap?
These circuits are part of a much larger design and will be mounted on a multilayer PCB board with seperate planes for power +5v, + 28, analog ground, digital grounds.
I'm not an electronics engineer. I'm electronics technician where I work doing some engineering design work. I have a pretty good electronics background just not alot of board layout designs.
Help is always greatly appreciated.
Thanks,
Brian