n-XYTER - Read-out ASIC for High Resolution Time and Amplitude Measurements

Introduction

The n-XYTER ASIC was developed in context of the EU-FP6 Integrated Infrastructure Initiative NMI3 in the Joint Research Activity DETNI as the common read-out solution for three different, solid converter based neutron counting area detectors. Because of the the statistical, non-triggerable nature of neutron data to be processed, the internal architecture of the chip is self triggered and data driven. It integrates 128 channels with low noise preamplifiers and shapers. Each channel has two different shapers with distinct time constants, one optimized for timing resolution, the other one optimized for energy (pulse height) resolution. A peak detector connected to the slower shaper allows for the application of a spectroscopic amplitude measurement. An internal time stamp generator provides the temporal reference that may be employed to identify time coincidences of signals on different detector channels and thus correlate their spatial point of origin. For testability and calibration purposes, a charge injector with adjustable pulse height was implemented. The bias settings and various other parameters can be controlled via a standard I2C-interface.

Key Features

• mixed signal chip
• process: AMS 0.35 μm CMOS
• 128 channels
• 1 test channel with analogue diagnostic output
• architecture for AC-coupling, employable for positive and negative signals
• self triggered, data driven de-randomizing, sparcifying readout at 32 MHz
• digital time stamp output
• analogue peak hight output
• maximum data loss at 32 MHz average input rate over 16 μs: 4%
• analogue pile-up registry
• programmable dead time
• local threshold adjustment
• Dynamic Range: 120000 e
• Shaping time and noise performance:
  • 18 ns fast shaper at 30 pF input, 850 enc for positive signals, 1000 enc for negative signals
  • 140 ns slow shaper at 30 pF input, 600 enc
• Timing resolution ~ 2-3 ns, time stamp resolution 1 ns

Documentation

• n-XYTER Reference Manual, describes in detail electrical specifications, operating conditions and port definitions of the readout chip n-XYTER 1.0.
  • Version 1.50 (Draft) of 15.12.2009 (Improvement in the documentation of time-stamp generation)
  • Version 1.40 (Draft) of 25.05.2009 (Improvements on strategies for finding Vcm settings and help for compensation of temp co.)
  • Version 1.30 (Draft) of 29.03.2009
  • Version 1.30 (Draft) of 29.07.2008
  • Version 1.30 (Draft) of 24.07.2008
  • Version 0.90 of 28.02.2008

Papers and Presentations

• C.J. Schmidt et al., Test results on the n-XYTER ASIC, a self triggered, sparcifying readout ASIC, Topical Workshop on Electronics for Particle Physics 2007, TWEPP-07, 3-7 September 2007, Prague
• A.S. Brogna et al., N-XYTER, a CMOS read-out ASIC for high resolution time and amplitude measurements on high rate multi-channel counting mode neutron detectors, Nucl. Instrum. Methods A 568 (2006) 301–308

-- WalterFJMueller - 30 Apr 2008