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# Schematics PDF
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# Quick design explanation
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Here is a quick explanation of the design where each different part is
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Here is a quick explanation of the design where each different part is
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described in a few words. For more information, read the paper
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described in a few words. For more information, read the paper
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... | @@ -7,20 +7,23 @@ schematics PDF can be found here: document:"ADC board design PDF". All |
... | @@ -7,20 +7,23 @@ schematics PDF can be found here: document:"ADC board design PDF". All |
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the design has been done on KiCAD. For a better experience, it is
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the design has been done on KiCAD. For a better experience, it is
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advised to download the last KiCAD project from the repository. For
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advised to download the last KiCAD project from the repository. For
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example, this would give the reader the possibility to open the
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example, this would give the reader the possibility to open the
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components datasheet with three clicks (double click on the component
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components'datasheets with three clicks (double click on the component
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and then on the "Documentation" tab).
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and then on the "Documentation" tab).
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-----
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## The whole board
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## The whole board
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WholeBoard.jpg
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WholeBoard.jpg
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On this card will be connected all the future time measurement elements
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On this card will be connected all the future time measurement elements.
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will be connected. So, the goal of this board is only to convert the
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So, the goal of this board is only to convert the analog data in
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analog data in numerical ones. As we want the best possible resolution
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numerical ones. As we want the best possible resolution for the ADC, we
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for the ADC, we pay extremely attention to the noise generated by the
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pay extremely attention to the noise generated by other components. This
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other components. This board is a carrier card for the
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board is a carrier card for the
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[MicroZed](http://zedboard.org/product/microzed) board which will be
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[MicroZed](http://zedboard.org/product/microzed) board which will be
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used to process incoming data.
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used to process incoming data.
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The design schematics are divided into 5 different parts :
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The design schematics are divided into 5 different parts :
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\> \# the first ADC,
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\> \# the first ADC,
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... | @@ -33,6 +36,8 @@ This schematic is only to show the different connections between these |
... | @@ -33,6 +36,8 @@ This schematic is only to show the different connections between these |
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different parts. In addition to the power lines and data lines, we can
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different parts. In addition to the power lines and data lines, we can
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see the SPI bus between the MicroZed and both the ADC.
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see the SPI bus between the MicroZed and both the ADC.
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-----
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## The two ADC
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## The two ADC
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As the schematics for the two ADC are the same, we only put one of them
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As the schematics for the two ADC are the same, we only put one of them
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... | @@ -49,10 +54,13 @@ A particular attention is given to the power supply decoupling. Multiple |
... | @@ -49,10 +54,13 @@ A particular attention is given to the power supply decoupling. Multiple |
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capacitors with multiple values are placed to reduce the impedance on a
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capacitors with multiple values are placed to reduce the impedance on a
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large bandwidth and then avoid the noise to disturb the measurements.
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large bandwidth and then avoid the noise to disturb the measurements.
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This has been done as well for the analog power lines as for the digital
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This has been done as well for the analog power lines as for the digital
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ones.
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ones. To have the lowest ESR and the highest SRF, we only use ceramic
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capacitors (C0G/NP0 when possible, otherwise we use X7R).
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The clock signal arrives from the splitter on a differential line.
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The clock signal arrives from the splitter on a differential line.
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-----
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## The clock splitter
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## The clock splitter
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clockSplitter.jpg
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clockSplitter.jpg
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... | @@ -64,6 +72,8 @@ filter the input clock signal. The parameters of that filter can be set |
... | @@ -64,6 +72,8 @@ filter the input clock signal. The parameters of that filter can be set |
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using the `FILTA` and `FILTB` inputs. To be able to change the filter
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using the `FILTA` and `FILTB` inputs. To be able to change the filter
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and to adjust it to our needs, we put these inputs on jumpers.
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and to adjust it to our needs, we put these inputs on jumpers.
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-----
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## The power Supply
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## The power Supply
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PowerSupply.jpg
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PowerSupply.jpg
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... | @@ -72,12 +82,32 @@ We need enough power to supply all the components on the board but also |
... | @@ -72,12 +82,32 @@ We need enough power to supply all the components on the board but also |
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the MicroZed board. Furthermore, these components needs different
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the MicroZed board. Furthermore, these components needs different
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voltage levels.
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voltage levels.
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The first stage is a buck converter. It is use to convert the voltage
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The first stage is a buck converter. It is used to convert the voltage
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from 12 V to 5V DC. These 5 V are needed by the MicroZed board. We then
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from 12 V to 5V DC. These 5 V are needed by the MicroZed board. We then
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converter these 5 V in a 3.3 V one. This last is used to supply the
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converter these 5 V in a 3.3 V one. This last is used to supply the
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clock splitter. Finally, two LDO are used to regulate the digital and
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clock splitter. Finally, two LDO are used to regulate the digital and
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analog power supplies of the ADC.
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analog power supplies of the ADC.
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We put two different connectors for the power : a DC barrel jack and a
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MINI DIN 4. To be sure to have the right voltage polarity, we put a
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double rectifier bridge using Schottky diodes. These diodes are chosen
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to avoid a too high voltage drop at the input. A diode is also placed
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next the barrel jack to protect the circuit in case the polarity is
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inverted.
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The LM43603 has been chose because its switching frequency can be set up
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to 2.2 MHz. In addition, this frequency can be changed using an external
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clock. These high frequencies are easier to shield than lower ones. A
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further reason for choosing this buck converter is that its switching
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MOSFETS are inside the chip package, reducing considerably the "hot
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loop".
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Instead of using big capacitors at the input and the output of the
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converter, we decided to use different values to catch the high
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harmonics and then improve the noise rejection.
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-----
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## External connections
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## External connections
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FCI.jpg
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FCI.jpg
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