... | ... | @@ -4,12 +4,12 @@ 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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[Realisation of a low noise acquisition board : design
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choices](https://www.ohwr.org/project/r19-tdc-del-a/uploads/2de2fdf069410a4799144539158fcd45/Realisation_of_a_low_noise_acquisition_board__design_choices.pdf).
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The schematics PDF can be found here: document:"ADC board design PDF".
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All 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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example, this would give the reader the possibility to open the
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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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The PDF of the schematics can be found here: document:"ADC board design
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PDF". All the design has been done on KiCAD. For a better experience, it
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is advised to download the last KiCAD project from the repository and
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explore it. For example, this would give the reader the possibility to
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open the components' datasheets with three clicks (double click on the
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component and then on the "Documentation" tab).
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-----
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... | ... | @@ -32,22 +32,21 @@ The design schematics are divided into 4 different parts : |
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\> \# the MicroZed Board connections,
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\> \# the power supply
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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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see the SPI bus between the MicroZed and both the ADC.
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This first picture is only to show the different connections between
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these different parts. In addition to the power lines and data lines, we
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can see the SPI bus between the MicroZed and both the ADC. This bus can
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be used to configure the ADC.
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-----
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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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here.
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here. The other one is available
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[here](https://www.ohwr.org/4345).
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/4333
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\*To see the other ADC design schematic click
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[here](https://www.ohwr.org/4345)*
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We have two inputs for each ADC. On each input are one SMA connector for
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ground referenced signals and two others for differential ones. All
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inputs have an impedance around 50 ohm on a two decades bandwidth
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... | ... | @@ -75,7 +74,7 @@ line. |
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This part is used to synchronise both the ADC by giving them the same
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clock signal. This clock splitter allows us to use different clock
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frequencies in a range from 5 MHz to 125 MHz. This component can also
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filter the input clock signal. The parameters of that filter can be set
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filter the input clock signal. The parameters of the 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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and to adjust it to our needs, we put these inputs on
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jumpers.
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... | ... | @@ -92,23 +91,23 @@ voltage levels. |
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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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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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analog power supplies of the ADC.
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convert these 5 V in a 3.3 V one. This last is used to supply the clock
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splitter. Finally, two LDO are used to regulate the digital and analog
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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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next to 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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The LM43603 has been chosen because its switching frequency can be set
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up to 2.2 MHz. In addition, this frequency can be changed using an
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external clock. These high frequencies are easier to shield than lower
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ones. A further reason for choosing this buck converter is that its
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switching MOSFETS are inside the chip package, reducing considerably the
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"hot 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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... | ... | @@ -122,7 +121,8 @@ harmonics and then improve the noise rejection. |
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The connections to the MicroZed board are done via its FCI connectors.
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All these inputs can be configured to work in LVDS. As the output of our
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ADC are already in LVDS, it fits ideally with our project.
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ADC are already in LVDS, this configuration fits ideally with our
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project.
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In addition to these connections to the ADC, we also provide the board
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other connections to be able to use the other MicroZed GPIO.
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