The RatCAP Front-End ASIC
| Autor: | Sachin Junnarkar, V. Radeka, Roger Lecomte, Sri Harsha Maramraju, Rejean Fontaine, Paul O'Connor, S. P. Stoll, D. Schlyer, Paul Vaska, Grzegorz Deptuch, Jack Fried, Jean-Francois Pratte, S. Krishnamoorthy, C. Woody |
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| Rok vydání: | 2008 |
| Předmět: |
Physics
Nuclear and High Energy Physics Discriminator Preamplifier business.industry Electrical engineering Avalanche photodiode Noise (electronics) Optics Nuclear Energy and Engineering CMOS Application-specific integrated circuit Low-power electronics Nuclear electronics Image noise Electronic engineering Electrical and Electronic Engineering business Encoder |
| Zdroj: | IEEE Transactions on Nuclear Science. 55:2727-2735 |
| ISSN: | 0018-9499 |
| DOI: | 10.1109/tns.2008.2004275 |
| Popis: | We report on the design and characterization of a new ASIC for the RatCAP, a head-mounted miniature PET scanner intended for neurological and behavioral studies of an awake rat. The ASIC is composed of 32 channels, each consisting of a charge sensitive preamplifier, a 5-bit programmable gain in the pole-zero network, a 3rd order bipolar semi-Gaussian shaper (peaking time of 80 ns), and a timing and energy discriminator. The energy discriminator in each channel is used to arm the zero-crossing discriminator and can be programmed to use either a low energy threshold or an energy gating window. A 32-to-1 serial encoder is embedded to multiplex into a single output the timing information and channel address of every event. Finally, LVDS I/O were integrated on chip to minimize the digital noise on the read-out PCB. The ASIC was realized in the TSMC 0.18 mum technology, has a size of 3.3 mm times 4.5 mm and a power consumption of 117 mW. The gate length of the N-channel MOSFET input device of the charge sensitive preamplifier was increased to minimize 1/f noise. This led to a factor 1.5 improvement of the ENC with respect to the first version of the ASIC. An ENC of 650 e-rms was measured with the APD biased at the input. In order to predict the achievable timing resolution, a model was derived to estimate the photon noise contribution to the timing resolution. Measurements were performed to validate the model, which agreed within 12%. The coincidence timing resolution between two typical LSO-APD-ASIC modules was measured using a 68Ge source. Applying a threshold at 420 keV, a timing resolution of 6.7 ns FWHM was measured. An energy resolution of 18.7% FWHM at 511 keV was measured for a 68Ge source. |
| Databáze: | OpenAIRE |
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