OriginalSystemSpec
These are the original system specifications that were used for the design. These were made in December 2010 and January 2011. Certain features have been changed when designing the card in March 2011.
FMC Time to Digital Converter: FMC TDC 1ns 5cha
System specifications
- 5 inputs, TTL with 50 Ohm termination. Made termination software selectable
- Time tags apply to rising edges of inputs. They are made of two parts: 32 bits for the UTC second and as many bits as needed for the fractional part within the second (will depend on final choice of resolution).
- 500 ps resolution or better.
- Accuracy (of time-tag differences between channels): /- (250 ps timebase accuracy).
- Timebase accuracy: +/- 4ppm.
- Implementation details: timebase from a local TCXO on FMC card and needs calibration. Much better accuracy will be reached when used on a White Rabbit enabled FMC carrier.
- External inputs need to be protected against +15V pulses with a pulse width of at least 10us @ 50Hz (with protection diodes if possible).
- SMC connectors for all inputs. Actually lemo connectors are preferred by the main client (CERN's TE-ABT group), to be discussed. Decided to use LEMO 00 connectors
- Minimum input pulse width: 100 ns. Narrower pulses should be ignored.
- A circular buffer will contain time tags for at least the last 100 input pulses. These time tags will at first be rough UTC (counter initialized by SW) giving ~ms accuracy. Later, with a WR-enabled solution, they can be much more accurate. Differences between channels will not suffer from this accuracy problem because the offset with respect to UTC will cancel.
- Programmable (enable/disable) host interrupts on all 5 channels.
- FMC mezzanine using a Low Pin Count (LPC) connector.
- Vadj is 2.5V.
Erik van der Bij - 18-03-2011