16 bits ADC - MAX1162
16 bits ADC - SPI - MAX1162
Fig. 1 16 bits SPI ADC
Description:
This board is a 16 bits ADC with an SPI interface. It is based around 2 Maxim chip: the 16 bits analog-to-digital converter MAX1162, and a voltage reference MAX60xx. A different voltage reference chip was selected for this board than for the DAC SPI board, because of increased resolution. The MAX60xx voltage reference have a precision of 0.2%, whereas the MAX61xx voltage reference is about 1%. The DAC has a resolution of 8 bits, against 16 bits for this ADC.
It connects to a host with an SPI bus, up to 10 MHz.
The voltage reference can be choosen between MAX6012, 6021, 6025, 6030, 6041 or 6045 for a voltage reference (and maximum input voltage) of 1.247, 2.048, 2.5, 3, 4.096 or 4.5 V respectively.
The board can be powered from 4.5 to 5V. This is limited by the analog sectoin of the converter.
Schematic:
The schematic is as simple as it can get. R1/C1 filter the power supply to the analog section of the chip. C2 filters the digital section.
IC2 , a high precision chip, provides voltage reference to the ADC chip IC1.
IC2 can be selected from the MAX 60xx chips listed above. It determines the range and resolution of the board.
Specifications:
Input voltage 4.5 to 5V
InterfaceSPI 10MHz
CS selectable by jumper
Iutput voltage0 to Vref
16 bits resolution
Voltage referencedefined by chip MAX60xx
The MAX6041 was selected for it, simply because I had one in my drawer. It gives a voltage reference of 4.096 V, which over 16 bits gives a resolution of 62.5 uV. (62.5uV * 2^16 = 4.096V)
The board is powered with a 5V processor board.
The CS signal is pulled high by default with R2. U1 is active with CS low, so it keeps IC1 inactive by default. JP2 allows to select which CS line from the SPI interface is used.
The SPI interface is common across the SPI boards, and provides the following signals: SCK, MISO, MOSI, 3 chip select signals and power supply.
The input is on JP3, also common across analog boards.
Fig. 2 16 bits SPI ADC schematic
Construction:
The PCB fits on a small single sided board. The PCB is designed to fit on one of the typical size for the board designed here. All components are on the top side.
Fig. 3 16 bits ADC SPI layout
Start with the lowest components, IC1 and IC2, and continue with the higher ones. (On the top photo, this is a beta board, where the SPI connector is on the wrong side. This is corrected in the PDF or eagle file.
The connectors JP1 and JP3 are optional. You can either solder cables directly on the board, or use connector to connect various boards together.
Pads 1 to 4 can be drilled to 3mm to fix the board, or put spacers.
| 16 bits SPI ADC Component list |
|---|
| C1, C2, C4: 100 nF smd 1206 C3: 10 nF smd 1206 R1: 10 R2: 47k smd 1206 or 0603 IC1: MAX1162 U2: MAX6012, 6021, 6025, 6030, 6041 or 6045 JP2: jumper 3x2 JP1: Connector AMP MT 8 pins male (optional) JP3: Connector AMP MT 3 pins male (optional) |
How to use / Testing:
To check the board, connect the board to an SPI interface. Leave jumper off JP2 for now. Power up the board.
Check you have the Vcc supply on IC1 and the reference voltage.
To check the ADC is working, you need a processor board running the SPI ADC tutorial. Just make sure you set the switch on JP2 to the proper CS line.
Files and links:
Eagle PCB and schematics files for 16 bits SPI ADC.PDFs of PCB, layout and schematics of 16 bits SPI ADC.
Maxim MAX1162.
Maxim MAX6012, MAX6041, MAX6045.