A/D converter lines

How to design an A/D converter circutry

The Analog to Digital converter lines are located on the Acme Systems modules on the following pins:

Signal Description RoadRunner Arietta Aria Terra Fox G20
3.3V 3.3 volt power line J4.5 D14.1 J6.1
AVDD Clean 3.24V out for A/D circuitry D14.2 J6.33
VREF A/D voltage reference input W19 D14.3 J6.34
AGND Analog GND D14.4 J6.35
AD0 Analog input 0 PD19 J4.34 W20 D14.5 J6.30
AD1 Analog input 1 PD20 J4.36 W21 D14.6 J6.29
AD2 Analog input 2 PD21 J4.38 W22 D14.7 J6.28
AD3 Analog input 3 PD22 J4.40 W23 D14.8 J6.27
AD4 Analog input 4 PD23
AD5 Analog input 5 PD24
AD6 Analog input 6 PD25
AD7 Analog input 7 PD25
AD8 Analog input 8 PD27
AD9 Analog input 9 PD28
AD10 Analog input 10 PD29
AD11 Analog input 11 PD30
GND Digital GND J4.9 W1 D14.10 J6.40

On Arietta and Aria the A/D resolution is 10 bits so using for example a Vfer or 3.3 volt the minimal resolution is about 3.2 mV.

On Arietta the VREF line is wired internally to the 3V3 volt so is not possible to change it.

By wiring the VREF pin to AVDD or VDD (max 3.3 volt) it's possible to read a max voltage of 3.24 volt with a resolution of 10 bit (1024 samples). In this way the max sample resolution we obtain is about 3.24V/1024 ~= 3mV.

On VREF no voltage higher than 3.3 Volt can be applied. If you need to read a higher signal use a schematic like this:

A module called DAISY-20 is available to use these lines in the range of 0 to 10 volts. Elsewhere use this schematic to test quickly the A/D lines:

Sergio Tanzilli - tanzilli@acmesystems.it
http://www.tanzilli.com - https://github.com/tanzilli