The FMC DEL 1ns 4cha delay module will take in a TTL trigger signal
and will send it out to four different outputs. The delay from the
trigger input to each of the outputs can be set independently in a range
from 600 ns to 120 seconds. It is implemented using a dedicated
time-to-digital converter IC from the European company
TTL, outputs capable of driving a 50 Ohm load, > 2 V/ns slew rate
Pulse delay: on trigger, generates a pulse or series of pulses of given width and repetition rate on chosen outputs after a certain time programmed by the user. Single channel TDC: time tags incoming trigger pulses available via a circular buffer. Pulse generator: produces a pulse or a series of pulses of arbitrary length and repetition rate starting at a given UTC/TAI time.
Minimum input pulse width
100 ns. Pulses below 24 ns are ignored.
Maximum input pulse rate
1 MHz (minimum pulse spacing: 1 us)
Output pulse width
50 ns - 1 s (10 ps resolution)
Output pulse spacing
100 ns - 1 s (10 ps resolution)
Trigger to output delay
600 ns (min) to 120 seconds (max). Independent setting for each channel.
Output pulse repeat count (train generation)
1 - 65536 pulses or infinity (continuous mode)
± 2.5 ppm
The timebase from a local TCXO on FMC card needs calibration. The 2.5 ppm accuracy is the one of the on-board TCXO. Cesium-quality accuracy will be reached when used on a White Rabbit enabled FMC carrier.
TDC Precision (std. dev)
Baseline: < 300 ps average, < 1 ns peak-to-peak (minimum delay setting of 600 ns).
Accuracy is as good as the time base, e.g. for a delay of 1 s using internal time base, the worst case error will be (2.5 ppm x 1 s) = 2.5 us. The accuracy can be greatly improved by locking the card to GPS/Cesium clock source through White Rabbit.
Time tag buffer
1024-entries circular buffer with time tags for input/output pulses. Buffer interrupt (with timeout/threshold coalescing)