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PICOSTRAIN Capacitor Choice

For correct operation it is necessary to select the right capacitor value and the right capacitor material. Following the recommendation for the comparator circuit, the discharge time is about
t = 0.7*RSG*CLoad

In measurement range 2 the time interval measurement uses not only the high-speed unit of the TDC but also the reference clock (pre-divider). Doing this the measurement range of the TDC is extended to 100 µs. This allows update rates up to 10 kHz. For higher update rates the discharge time must be reduced. At update rates higher than 10 kHz measurement range 1 is recommended.

The following values are recommended for measurement range 2:

RSGCLoad
1 kOhm68 nF
350 Ohm220 nF

Capacitor material

The capacitor is an important part of the circuit and has direct influence on the quality of the measurement and the stability with temperature

We recommend the following materials (group 1):

  • CFCAP (Multilayer ceramic from Taiyo-Yuden)
  • C0G or NP0 ceramics
  • Polystyrene
  • Polyvenylsulfid

The PICOSTRAIN integrated circuits are realized without any analog component. Again, acam uses its TDC technology to set new standards in circuit design and takes the advantages of this principle like:

  • 2 channels with typ. 50 ps rms resolution
  • 65 ps Bin size
  • Measurement range 3.5 ns to 1.8 µs
  • 15 ns pulse-pair resolution with 4-fold multihit capability
  • 4 events can be measured arbitrarily against each other
  • Windowing for precise stop enable

Also these materials may be used but with some small losses in temperature stability (group 2):

  • X7R
  • Polyester

The following materials must not be used (group 3):

  • Z0G