Difference between DGround/AGround?

[Megahertz]

I am making a circuit involving MCP3204 (ADC). This IC has 3 pins which I am unsure about and they are Digital Ground + Analog ground + Vref. Can someone please confirm on where to connect them. I have 3 pots which will be connected to CH0 ~ Ch2. They will have one side to +V and Second end to Ground with middle pin connected to the Channels 0 to 2. Where should AGnd be connected? I only have one ground in the whole PCB which will be connected to the DGnd as well I guess. Also VRef will be VDD, so should I just connect VRef to VDD direct?

[HenrikOlsson]

In a digital circuit there can be quite a bit of noise on the ground. When mixing digital and analog circuitry it's common to separate the grounds for the digital circuits from the ground for the analog circuit and then connect them together at a single common point. Since the ADC-chip uses digital signals to communicate with the uC it needs a reference for those signals (Digital Ground) and a reference for the analog signal (Analog Ground). If this doesn't make any sense, just connect them to ground.

The analog and digital ground pins are covered in the datasheet, section 6.4 and 6.5.

The voltage you feed into the VRef input is the voltage on the analog input which will give you a full scale reading. Since this is a 12 bit converter the result you'll get will be in the range 0-4095. If you feed 4.096V into the VRef input you'll get your results in units of 1mV. If you feed 2.048V into the VRef input you'll get your results in units 500uV and so on. In your case, with the pots connected across the power supply you want to connect VRef to the positive rail (5V?).

Please see the datasheet, section 4.2 for more info on the VRef input.

/Henrik.

[Megahertz]

Thanks a lot Henrik.