Fasti - The Analog/Digital Conversion board (CAD)

The Conversion Subsystem (CAD) consists of a small number (4 for NICMOS3 and Hawaii) of analog to digital converters and some glue logic. There are a small part of approach we are considering for the CAD, and we can choose the best fit for each application.

16 bits conversion

This is the standard approach. It is well suited for medium velocity applications (around .5Mhz per channel).

14 bits conversion

This new approach proves successfully in fast (speckle) instruments. It uses fast 14 bit converters to digitize each pixel many times (4-16) and then apply a fast digital filter. This approach appeares best suited for slower data rates at low noise (less than 250Khz), and faster rates at a reduced resolution.

1 Bit conversion

This approach is suited for very fast (more than 16Mhz) photon counting mode of L3CCD Marconi detectors.