OWLs: A mixed-signal ASIC for optical wire-less links in space instruments

Comunicación presentada al "AMICSA 2012" celebrado del 27 al 28 de Agosto del 2012 en Noordwijk (Holanda).-- et al.This paper describes the design of a mixed-signal ASIC for space application and the techniques employed for radiation hardening and temperature effects compensation. The work is part of a planned long-term effort and collaboration between "Instituto de Microelectrónica de Sevilla (IMSE)", "Universidad de Sevilla (US)", and "Instituto Nacional de Técnica Aeroespacial (INTA)" aimed to consolidate a group of experienced mixed-signal space-ASIC designers. The initiative is partially funded by the Spanish National Research Program. The ASIC performs the function of an optical digital transceiver for diffuse-light intra-satellite optical communications. It has been designed in a 0.35μm CMOS technology from austriamicrosystems (ams). The chip has been manufactured and verified from a functional perspective. Radiation characterization is planned for the third quarter of 2012. Power- and temperature-stress tests, as well as life-tests are also planned for this next quarter, and will be carried out by Alter Technology TÜV Nord S.A.U. Given the previous characterization of the technology [1] and the hardening techniques employed in the design and layout, radiation is not expected to be a problem. The specified environmental limits are a pedestal hard limit of 50KRads with the goal of maximizing TID tolerance, SEU and SET LET-thresholds above 70MeV/(mg/cm2), and latchup free behavior up to the same LET limit. Concerning temperature, the specified operation range is from -90 to +125ºC, while the non-operating temperature range is from -135 to +150ºC.This work has been partially supported by the Spanish Plan Nacional de Investigación of the Ministerio de Ciencia e Innovación (MICINN), under projects MEIGA (AYA2009-14212-C05-04 and AYA2008-06420-C04-02).Peer Reviewe

Evaluation of the AMS 0.35 μm CMOS technology for use in space applications

Trabajo presentado al "AMICSA 2012" celebrado del 27 al 28 de Agosto del 2012 en Noordwijk (Holanda).-- et al.The design of mixed-signal ASICs requires a detailed knowledge of the behaviour of the technology which exceeds the needs of digital designs. For space applications, with its extended temperature and radiation environment, the job of the mixed-signal designer is more difficult as in most cases commercial foundries do not have or make available data on the behaviour of their devices under those new conditions. The first step has been to develop a plan to assess and characterize a commercial (AMS) 0.35μm CMOS technology when exposed to radiation or to temperatures below the standard industrial or automotive ranges. Development of a RHBD digital library is also in progress. The results is being initially applied in the design of two ASICs for instrumentation for missions to Mars. Three different characterization test chips have been designed with several objectives in mind: a) evaluate the behaviour of the individual devices at temperatures down to -110C; b) verify the algorithms to map the geometries of enclosed layout transistors; c) evaluate the impact of Total-Ionization-Dose (TID) on devices (Vth drift, leakage) and heavy-ions on single-event-effects (SEE). Each chip contained five multiplexed arrays of 4 x 4 transistors, allowing access to a maximum of 80 transistors using only 17 package pins. Temperature tests have been performed at IMSE-USE, and INTA. TID tests have been made in the facilities of the Laboratorio de Radiofísica of the Universidad de Santiago de Compostela (Spain) (LR-USC). Prior to the SEE tests, which have been made at the Heavy-Ion Irradiation Facility in the University of Louvain-la-Neuve (HIF-UCL), the SEE test system was debugged using a Californium (Cf-252) source at the Centro Nacional de Aceleradores of the University of Sevilla (CNA-US). Test results show that with the standard layout procedures for leakage reduction in NMOS transistors, the leakage and voltage drifts caused by radiation up to 300 krad are acceptable with slightly increased design margins for threshold voltage. Drift effects are more pronounced in transistors with close to minimum dimensions, and in transistors with thick oxide, intended to operate with 5 V supply. The behaviour at low temperatures did not show significant deviations from that predicted by the foundry models. LET threshold values were measured in the first test chip using shift-register chains with cells constructed using different layout styles. SEU LET threshold for the standard library cells was in the range of 5.5 MeV/mg/cm2; for SRs built using ringed-drain NMOS and improved substrate and guard connections, LET threshold increased to 15.6 MeV/mg/cm2, and to 35.2 MeV/mg/cm2 when fully enclosed layouts were used. Latch-ups were observed only in the logic implemented with the standard library, with a LET threshold in the order of 9 MeV/mg/cm2, but was not observed in the custom-designed digital cells up to a LET of 67.7 MeV/mg/cm2.Peer Reviewe

Four-channel self-compensating single-slope ADC for space environments

A multichannel high-resolution single-slope analogue-to-digital converter (SS ADC) is presented that automatically compensates for process, voltage and temperature variations, as well as for radiation effects, in order to be used in extreme environmental conditions. The design combines an efficient implementation by using a feedback loop that ensures an inherently monotonic and very accurate ramp generation, with high levels of configurability in terms of resolution and conversion rate, as well as input voltage range. The SS ADC was designed in a standard 0.35 μm CMOS technology. Experimental measurements of the performance and stability against radiation and temperature are presented to verify the proposed approach. © The Institution of Engineering and Technology 2014.Peer Reviewe

A Front-End ASIC for a 3-D Magnetometer for Space Applications by Using Anisotropic Magnetoresistors

This paper presents an application-specific integrated circuit (ASIC) aimed for an alternative design of a digital 3-D magnetometer for space applications, with a significant reduction in mass and volume while maintaining a high sensitivity. The proposed system uses magnetic field sensors based on anisotropic magnetoresistances and a rad-hard mixed-signal ASIC designed in a standard 0.35 μm CMOS technology. The ASIC performs sensor-signal conditioning and analogue-to-digital conversion, and handles calibration tasks, system configuration, and communication with the outside. The proposed system provides high sensitivity to low magnetic fields, down to 3 nT, while offering a small and reliable solution under extreme environmental conditions in terms of radiation and temperature.Peer reviewe

Gut microbiota composition is associated with body weight, weight gain and biochemical parameters in pregnant women

10 pages, 5 tables, 2 figures.-- Printed version published in July 2010.Obesity is associated with complications during pregnancy and increased health risks in the newborn. The objective of the present study was to establish possible relationships between gut microbiota, body weight, weight gain and biochemical parameters in pregnant women. Fifty pregnant women were classified according to their BMI in normal-weight (n 34) and overweight (n 16) groups. Gut microbiota composition was analysed by quantitative real-time PCR in faeces and biochemical parameters in plasma at 24 weeks of pregnancy. Reduced numbers of Bifidobacterium and Bacteroides and increased numbers of Staphylococcus, Enterobacteriaceae and Escherichia coli were detected in overweight compared with normal-weight pregnant women. E. coli numbers were higher in women with excessive weight gain than in women with normal weight gain during pregnancy, while Bifidobacterium and Akkermansia muciniphila showed an opposite trend. In the whole population, increased total bacteria and Staphylococcus numbers were related to increased plasma cholesterol levels. Increased Bacteroides numbers were related to increased HDL-cholesterol and folic acid levels, and reduced TAG levels. Increased Bifidobacterium numbers were related to increased folic acid levels. Increased Enterobacteriaceae and E. coli numbers were related to increased ferritin and reduced transferrin, while Bifidobacterium levels showed the opposite trend. Therefore, gut microbiota composition is related to body weight, weight gain and metabolic biomarkers during pregnancy, which might be of relevance to the management of the health of women and infants.The present study was supported by grants AGL2008-01440/ALI, Consolider Fun-C-Food CSD2007-00063 from the Spanish Ministry of Science and Innovation, AP-124/09 from Consellería de Sanitat (Valencia, Spain) and P06-CTS-02341 (Excellence Project PREOBE) from Consejería de Innovación, Ciencia y Empresa de la Junta de Andalucía. (Spain). M. C. C. was recipient of I3P fellowships from CSIC (Spain).Peer reviewe

Design methodology and development of mixed-signal ASICs for space applications in standard CMOS technology

Trabajo presentado a la 21st IFIP/IEEE International Conference on Very Large Scale Integration celebrada en Estambul del 7 al 9 de octubre de 2013.-- et al.The design of mixed-signal ASICs for on-board space applications can provide several advantages that would not otherwise be possible with discrete components. However, extreme environmental conditions in terms of radiation and temperature imply a detailed knowledge of the technology used while CMOS commercial foundries do not usually have or make available these data. The aim of this work is to overcome these obstacles and offer solutions for space applications based on mixed-signal ASICs in commercial CMOS technologies. This paper presents the methodology followed for the assessment of a commercial (Austria Microsystems, AMS) 0.35 µm CMOS technology and for the development of a radiation hardened by design (RHBD) digital library. In addition, the described methodology has been applied to the development of two mixed-signal ASICs. The first chip performs the function of an optical digital transceiver for diffused-light intra-satellite optical communications. The second one implements a front-end solution for sensor data acquisition and signal conditioning and consists in a set of configurable multi-mode dual slope ADCs with resolution up to 16 bits.Peer Reviewe

An adaptive approach to on-chip CMOS ramp generation for high resolution single-slope ADCs

Trabajo presentado al ECCTD celebrado en Alemania del 8 al 12 de septiembre de 2013.-- et al.Many image sensors employ column-parallel ADCs in their readout structures. Single-slope ADCs are ideally suited for these multi-channel applications due to their simplicity, low power and small overall area. The ramp generator, shared by all the converters in the readout architecture, is a key element that has a direct effect in the transfer characteristic of single-slope ADCs. Because a digital counter is inherently present in this conversion scheme, one common practice is to use a digital-to-analog converter driven by the counter to generate the ramp. Given the direct relationship between the DAC and the ADC transfer characteristics, one of the main issues is to ensure a sufficient linearity of the DAC, with special emphasis on its monotonicity. Very often, in particular when medium to high resolutions are aimed, this requires calibration of the DAC, which must be repeated every once in a while to account for temperature, process, power supply, and aging variations. This paper presents an inherently monotonic ramp generator with high levels of linearity and stability against any expected source of variations, combined with a very efficient realization and an inherent automatic adaptability to different resolutions. The ramp generator has been designed using radiation hardening by design (RHBD) techniques, allowing its use in space applications.Peer Reviewe

A front-end ASIC for a 16-bit three-axis magnetometer for space applications based on anisotropic magnetoresistors

Trabajo presentado a la XXVIII Conference on Design of Circuits and Integrated Systems celebrada en San Sebastián del 27 al 29 de noviembre de 2013.-- et al.Many space applications require the measurement of magnetic fields. This includes many scientific and meteorological instruments, as well as satellite attitude control systems. The most widely used method for measuring magnetic fields in space missions has been the use of fluxgate sensors, mainly due to their reliability, robustness and relatively small mass and volume with respect to the total size of the satellite. However, the current trends of cost reduction and standardization in aerospace technology tends towards the design of small satellites, commonly called nano-satellites or even pico-satellites, embodying a new challenge in the design of low-cost space instrumentation. In this scope, fluxgate sensors are massy and large enough so that their use is not addressable for these small satellites. This paper presents an alternative design of a three-axis magnetometer for the measurement of the strength and direction of an incident magnetic field in space applications, with a significant reduction in mass and volume while maintaining a high detectivity. The proposed system uses magnetic field sensors based on anisotropic magnetoresistances (AMR) and a radiation hardened by design (RHBD) mixed-signal ASIC that performs signal conditioning and analog to digital conversion up to 16 bits, and also handles calibration tasks, system configuration and communication with the outside. The use of an ASIC instead of discrete components reduces both weight and volume, and achieves improvements in performance and consumption. The proposed magnetometer provides high sensitivy to low magnetic fields up to 30 µG of resolution while offering a small, low cost and reliable solution for space applications.Peer Reviewe

SEE characterization of the AMS 0.35 µm CMOS technology

Trabajo presentado al Radiation Effects on Components and Systems celebrado en Oxford del 23 al 27 de septiembre de 2013.This work presents experimental results for the single-event effects characterization of a commercial (Austria Microsystems) 0.35 µm CMOS technology. It improves and expands previous results. The knowledge gained is being applied in the development of a RHBD digital library.Peer Reviewe