  The LAB4D is a new application-specific integrated circuit (ASIC) of the
Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR)
family, for use in direct wideband radio frequency digitization such as is used
in ultrahigh energy neutrino and cosmic ray astrophysics. The LAB4D is a single
channel switched-capacitor array (SCA) 12-bit sampler with integrated
analog-to-digital converters (ADC), developed in the TSMC 0.25um process. The
LAB4D, operating at 3.2GSa/s, contains 4096 total samples arranged in 32
windows, for a total record length of 1280ns. The 3dB bandwidth is
approximately 1.3GHz, with a directly-coupled 50ohm input. This represents a
factor of 16 increase in the sample depth and an increase in analog bandwidth
and sampling depth in comparison to the previous generation LAB3 digitizer.
Individually addressable windows allow for sampling and digitization to occur
simultaneously, leading to nearly deadtime-free readout for kHz readout rates.
All biases and current references are generated via internal digital-to-analog
converters (DACs), resulting in a stand-alone digitizer with no additional
support circuitry. In addition, the LAB4D contains sample cell timebase
trimming capabilities, reducing the intrinsic sample-to-sample time variance to
less than 5ps; an improvement of about 80%. This allows the LAB4D to be used in
precision timing applications with minimal post-hoc calibration.
