The WaveCatcher family of SCA-based 12-bit 3.2-GS/s fast digitizers

The recent progresses in detector developments have raised the requirements for the associated readout electronics. High-end oscilloscopes are well adapted for test and characterization setups, but their cost per channel is high and their number of channels very limited. Precision test benches can also make use of ADC-based fast digitizers, but most of these modules are expensive and the most performing house very few channels. The recent progress of high speed Switch Capacitor Arrays (SCA) now permits offering sampling rates far above 1 GHz over 12 bits at low cost and low power consumption. The WaveCatcher board family has thus been developed for proposing an alternative to ADC-based digitizers (or even oscilloscopes). It is based on the SAMLONG SCAs developed since 2010 with the AMS CMOS 0.35-μm technology. All boards offer a wide DC-coupled dynamic range of 2.5 V (with adjustable offset) coded over 12 bits, a bandwidth of 500 MHz and a sampling rate ranging between 0.4 and 3.2 GS/s, which allows them to finely sample high speed signals like very short pulses. The sampling depth is of 1024 samples. The number of channels goes from 2 for the USB-powered version packaged in a friendly plastic box to 64 (optionally 72) for the version housed in an autonomous mini-crate. Thanks to the servo-controlled matrix structure of SAMLONG and the care taken in the board design, the sampling time precision is of the order of 5 ps rms, which permits using the system as a high-resolution TDC between any pair of channels, as this precision remains constant between chips and boards. The boards offer a lot of functionalities, like threshold-triggering on any channel and numerous trigger modes including coincidence. All system versions house a 480-Mbits/s USB interface permitting an easy connection to PC and a good readout speed. In parallel to hardware and firmware developments, we developed a powerful and user friendly acquisition software running on PC and transforming the latter into a 2 to 64-channel oscilloscope. It permits saving data files directly on disk, and is currently used in most WaveCatcher system applications. An increasing number of labs or companies are now using the WaveCatcher boards worldwide on their test benches or physics experiments.