I finally got some spare time to try to finish up my ADC board. I used MCP3424 chip from Microchip, which has the capbility to work at 18, 16, 14 and 12 bit resolution, software selactable and it has 4ch (differential). For a specific use I needed a R/R rail to rail opamp (MCP6284) with shottky protection diodes as signal conditioners. The Board uses 5V, but has a standard circuit with N-Channel mosfet to manage 3.3V to/from 5V for I2C (hardware) to gadgeteer boards. This board need to be used in a middle power RF field very close to HF antennas, so I needed a R/R clean front-end to avoid RFI on the input.
Becouse I need 6 analog ch I used 2 MCP3424 chip on this board. I provide also a passthrough gadgeteer connector so you can attach 2 of this board obtaining 16ch, and a configuring jumper.
This ADC converter is not very fast indeed and it can reach 260 SPS at 12bit, but only 3.75 SPS at 18bit.
The board routing is just rough and not optimized nor gadgeteer compiant for the moment.
[Edit:] I used differential input as single- ended.
I’m thinking if may be better to have a single chip (4ch) board instead of two chip (6ch), becouse it will cost much less.
Any suggestion ?