FMC Time to Digital Converter: FMC TDC 1ns 5cha
Functional system specifications
- 5 inputs, TTL with 50 Ohm termination.
- Time tags apply to rising edges of inputs.
- 1 ns resolution or better.
- Accuracy (of time-tag differences between channels): /- (500 ps timebase accuracy).
- Timebase accuracy: +/- 4ppm.
- Implementation details: timebase from a local TCXO on FMC card and needs calibration. The 4ppm accuracy will only 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.
- Minimum input pulse width: 100 ns. Pulses shorter than 20ns 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.
- Clock for internal time base is fed to a 6th TDC channel from the FMC connector. This allows usage of the TCXO in the carrier, a WR-derived clock or one coming from alternative sources such as the e-SATA connectors in the PFC board.
Project Status
Date | Event |
06-12-2010 | Project start. |
14-12-2010 | First functional specification available for comments. |
Javier Serrano - 14 December 2010