FMC Time to Digital Converter | FMC TDC 1ns 5cha

The FMC TDC 1ns 5cha Time to Digital Converter mezzanine board houses 5 input channels. It can calculate time differences between pulses arriving to the channels with a precision of +-700 ps.
It can be carried by any of the carrier boards: SPEC or SVEC. It is implemented using a dedicated time-to-digital converter IC from the European company Acam chip in I-mode.

Linux software support for the board is available in the dedicated project FMC TDC SW.
The provided software comprises: Linux device driver based on ZIO and stacked on the SPEC or SVEC driver | User space libraries | Documentation.

Top view of TDC mezzanine board

System specifications

Input Channels 5 channels TTL with software selectable 50 Ohm termination.
Inputs need to be protected against +15V pulses with a pulse width of at least 10us at 50Hz
Channels enable Software controlled switch that enables/ disables all 5 channels
Timestamps buffer Circular buffer that keeps the last 128 pulses (256 rising and falling edges);
programmable interrupts implemented based on the number of accumulated timestamps or the amount of elapsed time
Timestamps precision (deviation) +/- 700 ps
Timebase accuracy +/- 4 ppm from a local TCXO on FMC card; much better accuracy would be reached when used on a White Rabbit enabled FMC carrier
Maximum input pulse rate 31.25 MHz from all 5 channels
Timestamps Timestamps apply to both rising and falling edges of incoming pulses;
on the software level the falling edges are only used for the calculation of the pulse width, ignoring pulses < 100 ns;
the rising edges are always subtracted between them
Minimum input pulse width 100 ns, narrower pulses are ignored on software level by subtracting a falling edge from the previous rising one
ACAM mode I-mode, 81ps resolution, +/- 500ps precision (6σ)
Connectors LEMO 00
FMC connector Low Pin Count
PCB 6 layers

Project documents


Hardware EDMS: EDA-02290
Gateware Gateware release
Linux device drivers Software release


Project Status

Date Event
06-12-2010 Project start.
14-12-2010 First specification available for comments.
09-03-2011 First schematic available. (need to replace LEDs)
18-03-2011 Second schematics design review held.
08-04-2011 First layout made. Review made, needs moving of components Review08042011.
11-04-2011 Layout being modified. Planning: 3 assembled prototypes by 16 May.
19-04-2011 New layout received. Design review on 20-04-2011.
20-04-2011 Review held Review20042011. Layout office modifies the design.
29-04-2011 Layout office finalised the design.
30-05-2011 Three prototypes ready.
01-06-2011 Start of writing firmware.
05-08-2011 Design specification review held. [[]]
08-08-2011 Basic functionality OK. Several issues found that need a new PCB layout.
16-12-2011 New PCB layout made. Production files will be generated.
02-02-2012 V2 schematics and PCB made. Will be reviewed on 7 February. Foresee production 8 boards for 23 March.
07-02-2012 Schematics reviewed: (review07022012). Improved schematics ready by 21-02-2012 for new review.
30-05-2012 V2 boards received.
30-08-2012 V3 schematics and PCB being made. Input circuit modified.
23-10-2012 V3 schematics and PCB ready.
15-11-2012 Ordered 60 V3 boards (10 for delivery by begin March end April 2013, 50 by begin May 2013). (order)
04-12-2012 Feedback on design received. Can use same PCB. Other changes may be handled in a V4.
25-03-2013 Will make V3-1 design (only change of BOM) to handle five issues.
08-04-2013 Working on: correcting two firmware bugs, writing documentation, writing software to test firmware.
26-04-2013 No known firmware bugs left. Writing calibration test program.
06-05-2013 V3-1 design ready (only change of BOM) to handle five issues.
13-05-2013 CERN received 9 pre-series V3-1 boards.
22-05-2013 CERN accepted quality of pre-series V3-1 boards.
Production of 50 series (original foreseen for delivery in May 2013) started.
09-08-2013 51 V3-1 boards received.

Eva Gousiou | Javier Serrano | Erik van der Bij | 17 January 2014