|
# FMC Time to Digital Converter: FMC TDC 1ns 5cha
|
|
# FMC Time to Digital Converter: FMC TDC 1ns 5cha
|
|
|
|
|
|
![](/uploads/4b197628f86ba882512ac7639047bedc/EDA-02290-V2_Top.jpg)
|
|
https://www.ohwr.org/2026
|
|
*Top view** - ([Bottom
|
|
|
|
view](https://www.ohwr.org/project/fmc-tdc/uploads/d8502fe05dbd0672080bc614732b770a/EDA-02290-V2_Bot.jpg),
|
|
-----
|
|
[Front
|
|
|
|
view](https://www.ohwr.org/project/fmc-tdc/uploads/1222bac3ae1d7fb7a7c973832760447c/EDA-02290-V2_Front.jpg))
|
|
|
|
|
|
|
|
# System specifications
|
|
# System specifications
|
|
|
|
|
|
- 5 inputs, TTL with software selectable 50 Ohm termination.
|
|
<table>
|
|
- Time tags apply to rising edges of inputs. They are made of two
|
|
<tbody>
|
|
parts: 32 bits for the UTC second and as many bits as needed for the
|
|
<tr class="odd">
|
|
fractional part within the second (will depend on final choice of
|
|
<td>Input Channels</td>
|
|
resolution).
|
|
<td><strong>5 channels TTL</strong> with software selectable 50 Ohm termination.<br />
|
|
- 500 ps resolution or better.
|
|
Inputs need to be protected against +15V pulses with a pulse width of at least 10us at 50Hz</td>
|
|
- Accuracy (of time-tag differences between channels): */- (700 ps*
|
|
</tr>
|
|
timebase accuracy).
|
|
<tr class="even">
|
|
- Timebase accuracy: +/- 4ppm.
|
|
<td>Channels enable</td>
|
|
- Implementation details: timebase from a local TCXO on FMC card
|
|
<td>Possibility to <strong>enable/ disable</strong> all 5 channels</td>
|
|
and needs calibration. Much better accuracy will be reached when
|
|
</tr>
|
|
used on a White Rabbit enabled FMC carrier.
|
|
<tr class="odd">
|
|
- External inputs need to be protected against +15V pulses with a
|
|
<td>Timestamps buffer</td>
|
|
pulse width of at least 10us @ 50Hz (with protection diodes if
|
|
<td><strong>Circular buffer</strong> that keeps the last <strong>128 pulses</strong> (256 rising and falling edges);<br />
|
|
possible).
|
|
programmable interrupts implemented based on the number of accumulated timestamps or the amount of elapsed time</td>
|
|
- LEMO 00 connectors for all inputs. SMC connectors may be mounted
|
|
</tr>
|
|
instead.
|
|
<tr class="even">
|
|
- Minimum input pulse width: 100 ns. Narrower pulses should be
|
|
<td></td>
|
|
ignored.
|
|
</tr>
|
|
- A circular buffer will contain time tags for at least the last 100
|
|
<tr class="odd">
|
|
input pulses. These time tags will at first be rough UTC (counter
|
|
<td>Timestamps precision (deviation)</td>
|
|
initialized by SW) giving ~ms accuracy. Later, with a WR-enabled
|
|
<td><strong>+/- 700 ps</strong></td>
|
|
solution, they can be much more accurate. Differences between
|
|
</tr>
|
|
channels will not suffer from this accuracy problem because the
|
|
<tr class="even">
|
|
offset with respect to UTC will cancel.
|
|
<td>Timebase accuracy</td>
|
|
- Programmable (enable/disable) host interrupts on all 5 channels.
|
|
<td><strong>+/- 4 ppm</strong> from a local TCXO on FMC card; much better accuracy will be reached when used on a White Rabbit enabled FMC carrier</td>
|
|
- 6-layer PCB.
|
|
</tr>
|
|
- FMC mezzanine using a Low Pin Count (LPC) connector.
|
|
<tr class="odd">
|
|
- Vadj 2.5V or higher.
|
|
<td>Maximum input pulse rate</td>
|
|
|
|
<td>?</td>
|
|
|
|
</tr>
|
|
|
|
<tr class="even">
|
|
|
|
<td></td>
|
|
|
|
</tr>
|
|
|
|
<tr class="odd">
|
|
|
|
<td>Timestamps</td>
|
|
|
|
<td>Timestamps apply to both <strong>rising and falling edges</strong> of incoming pulses;<br />
|
|
|
|
on the software level the falling edges are only used for the calculation of the pulse width, ignoring pulses < 100 ns;<br />
|
|
|
|
the rising edges are always subtracted between them</td>
|
|
|
|
</tr>
|
|
|
|
<tr class="even">
|
|
|
|
<td>Minimum input pulse width</td>
|
|
|
|
<td><strong>100 ns</strong>, narrower pulses should be ignored on software level by subtracting a falling edge from the previous rising one</td>
|
|
|
|
</tr>
|
|
|
|
<tr class="odd">
|
|
|
|
<td>ACAM mode</td>
|
|
|
|
<td><strong>I-mode</strong>, 81ps resolution, +/- 500ps precision (6σ)</td>
|
|
|
|
</tr>
|
|
|
|
<tr class="even">
|
|
|
|
<td></td>
|
|
|
|
</tr>
|
|
|
|
<tr class="odd">
|
|
|
|
<td>Connectors</td>
|
|
|
|
<td><strong>LEMO</strong> 00</td>
|
|
|
|
</tr>
|
|
|
|
<tr class="even">
|
|
|
|
<td>FMC connector</td>
|
|
|
|
<td>Low Pin Count</td>
|
|
|
|
</tr>
|
|
|
|
<tr class="odd">
|
|
|
|
<td>PCB</td>
|
|
|
|
<td>6 layers</td>
|
|
|
|
</tr>
|
|
|
|
</tbody>
|
|
|
|
</table>
|
|
|
|
|
|
-----
|
|
-----
|
|
|
|
|
... | | ... | |