16CH ADC SPI module with an ultra-high precision reference

16x 12bit ADC CH at 3MSps with a reference voltage capable of going as low as 1.3μVPP Noise!

3D Model of a 16CH ADC with SPI output and Ultra High PRecision Voltage Reference with MAC22231 and MAX6126 by Nadim Conti

What if you need a fast DAQ system capable of sampling up to 16CH at 3Msps? In case of an SPI capable microcontroller or CPU, here’s a solution using MAXIM MAX11131AUI+.

The MAX11131 is a 16CH SAR ADC IC with 70dB SINAD and not more than 1 +/- LSB INL and DNL. By pairing it with a MAX6126, this 42M3 module will give you 12bit of resolution from 0V to 3VDC.

Schematic of 16CH MAX11131AUI based ADC with ultra high precision voltage reference MAC6126 3V - By Nadim Conti
Schematic of a 16CH MAX11131AUI based ADC PCB with an ultra-high precision voltage reference (MAX6126 3V)

It is worth noting that this implementation requires a dual rail power supply, possibly with a low noise output, at both 5 and 3.3V (with MAX power out 50mW).

By controlling the module via a Raspberry Pi, it is in principle possible to hook up multiple modules so that one can build a pretty large DAQ system with many ADC channels (this is what I’m doing to build a 320CH ADC DAQ at INFN, even thou there I’m integrating everything on one single board by doing a copy and paste of this module on a bigger PCB).

Arduino (Atmega 328P Microcontroller from Atmel (Microchip)) should be able to read multiple modules, but not at 3MSPS since that speed requires a 48MHz clocked bus.

Assembly drawing of 16CH ADC with SPI output and ultra high precision voltage reference - by Nadim Conti
Assembly drawing. It should be possible to solder everything by hand.

Note: CS (chip select) and EOC (end of Conversion) pins are pulled high with a general purpose 10k resistor, this means that in normal operation ADC is disabled and EOC line pulled at 3.3V. When sampling EOC will be pulled low by the MAX11131 at each end of the conversion cycle.

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