MR1 Timing The measuring unit is actuated by a START signal and stopped by a STOP signal. Based on the position of the ring oscillator and the coarse counter the time interval between START and STOP is calculated with a 20 Bit measurement range.
Digital TDCs use internal propagation delays of signals through gates to measure time intervals with very high precision. The diagram on the right clarifies the principal structure of such an absolute-time TDC. Intelligent circuit structures, redundant circuitry and special methods of layout on the chip make it possible to reconstruct the exact number of gates passed by the signal. The maximum possible resolution strongly depends on the maximum possible gate propagation delay on the chip.
The BIN size (LSB) is typically 65 ps at 3.6 V and 25 °C ambient temperature. The gate propagation delay times strongly depend on temperature and voltage. Usually this is solved doing a calibration. During such a calibration the TDC measures 1 and 2 periods of the reference clock. The measurement range is limited by size of the counter: tyy = BIN x 26224 ~ 1.8 µs
Time (Condition)
Description
tph
2.5 ns
Minimum pulse width
tpl
2.5 ns
Minimum pulse width
tss
3.5 ns min.
1.8 µs max.
Start to Stop
trr
15 ns
Rising edge to rising edge
tff
15 ns
Falling edge to falling edge
tva
560 ns uncalibrated
4.6 µs calibrated
Last hit to data valid
txx
No limits
Time interval between the stop channels
tyy
1.8 µs
Measurement range
GP2 - Measurement Range 2
1 stop channel referring to one start channel
Typ. 65 ps resolution
2xTref pulse pair resolution
3-fold multihit capability
Measurement range 500 ns to 4 ms
Selectable rising/falling edge sensitivity
Powerful windowing functionality
The BIN size (LSB) is typically 65 ps at 3.6 V and 25 °C ambient temperature. The gate propagation delay times strongly depend on temperature and voltage. In measuring range 2 the result is the sum of different fine and coarse-count results. Therefore it is necessary in measuring range 2 to make a calibration. During a calibration the TDC measures 1 and 2 periods of the reference clock.
MR2 Timing Digital TDCs use internal propagation delays of signals through gates to measure time intervals with very high precision (see also measurement range 1).
In measurement range 2 the maximum time interval is extended using a pre-divider. The resolution in LSB remains unchanged by that. In this mode the high-speed unit of the TDC does not measure the whole time interval but only time intervals from START and STOP to the next rising edge of the reference clock (fine-counts). In between the fine-counts theTDC counts the number of periods of the reference clock (coarse-count).
The measuring unit is actuated by a START signal and stopped by a STOP signal. Based on the position of the ring oscillator and the coarse counter the time interval between START and STOP is calculated with a 26 Bit measurement range.
The measurement range is limited by size of the coarse counter:
tyy = Tref x 16384 ~ 4 ms
