Low-Voltage CMOS Temperature Sensor Design Using Schottky Diode-Based References

This paper presents the design of a fully differential sigma-delta temperature sensor using Schottky diode-based current references as a replacement for the traditional PN junction diode-based current references. This sensor was designed using the AMI 0.5um process through the MOSIS fabrication organization[l], and the chip performance will be evaluated and compared to the simulated results. The use of the Schottky diode and differential current sensing in the sigma-delta-type sensor allows for lower voltage operation and better noise performance

Low-Voltage CMOS Temperature Sensor Design Using Schottky Diode-Based References

Thermal management circuits have been used for many years in systems such as air conditioners, ovens, and engines. Today temperature sensors are often integrated onto the same chip as microprocessors, memory circuits, and other ICs to help control system temperature. In most commonly-used integrated CMOS temperature sensors, bias circuits that utilize a PN junction diode (or diode-connected PNP bipolar transistor) are used. This is due to the well-defined I-V temperature characteristics of the semiconductor PN junction. The forward bias voltage of this junction is approximately 0.7 V. As CMOS device geometries continue to shrink, so does the supply voltage. As the supply voltage decreases, this 0.7 V drop can be a limiting factor. The need for a device with a similar well-defined temperature characteristic and a lower forward-bias voltage becomes obvious. The design of a temperature sensor using the Schottky metal- semiconductor (MS) junction diode as a replacement for the tradition PN junction diode is presented in this work. The voltage required to forward-bias a Schottky diode is approximately half that of a PN junction diode, which allows for lower voltage operation. This research explores various temperature sensor topologies used for low-voltage temperature sensing. The topology used for the finished product is that of a fully differential sigma-delta temperature sensor. This topology was chosen for its excellent noise performance and good low-voltage operation. This sensor was designed and fabricated using the AMI 0.5um process through the MOSIS fabrication organization. The chip performance has been evaluated and compared to the simulated results to verify accurate low voltage operation over a wide temperature range. The final design achieves an effective resolution of 0.7 °C and consumes an average current of less than 1 μA at a rate of 20 temperature readings per second. Silicon results also confirmed that the fully differential sigma-delta sensor also shows better noise performance than a similar single- ended sigma-delta sensor. The Schottky-based current references used in the sensor achieve over 300 mV of additional low-voltage margin when compared to PN junction diode-based current references

Low-Voltage CMOS Temperature Sensor Design Using Schottky Diode-Based References

Abstract -This paper presents the design of a fully differential sigma-delta temperature sensor using Schottky diode-based current references as a replacement for the traditional PN junction diode-based current references. This sensor was designed using the AMI 0.5um process through the MOSIS fabrication organization[1], and the chip performance will be evaluated and compared to the simulated results. The use of the Schottky diode and differential current sensing in the sigma-delta-type sensor allows for lower voltage operation and better noise performance

Acridine orange leukocyte fluorography in mice

Simultaneous non-invasive visualization of blood vessels and nerves in patients can be obtained in the eye. The retinal vasculature is a target of many retinopathies. Inflammation, readily manifest by leukocyte adhesion to the endothelial lining, is a key pathophysiological mechanism of many retinopathies, making it a valuable and ubiquitous target for disease research. Leukocyte fluorography has been extensively used in the past twenty years; however, fluorescent markers, visualization techniques, and recording methods have differed between studies. The lack of detailed protocol papers regarding leukocyte fluorography, coupled with lack of uniformity between studies, has led to a paucity of standards for leukocyte transit (velocity, adherence, extravasation) in the retina. Here, we give a detailed description of a convenient method using acridine orange (AO) and a commercially available scanning laser ophthalmoscope (SLO, HRA-OCT Spectralis) to view leukocyte behavior in the mouse retina. Normal mice are compared to mice with acute and chronic inflammation. This method can be readily adopted in many research labs

Stearoyl-acyl carrier protein desaturases are associated with floral isolation in sexually deceptive orchids

The orchids Ophrys sphegodes and O. exaltata are reproductively isolated from each other by the attraction of two different, highly specific pollinator species. For pollinator attraction, flowers chemically mimic the pollinators’ sex pheromones, the key components of which are alkenes with different double-bond positions. This study identifies genes likely involved in alkene biosynthesis, encoding stearoyl-acyl carrier protein (ACP) desaturase (SAD) homologs. The expression of two isoforms, SAD1 and SAD2, is flower-specific and broadly parallels alkene production during flower development. SAD2 shows a significant association with alkene production, and in vitro assays show that O. sphegodes SAD2 has activity both as an 18:0-ACP Δ9 and a 16:0-ACP Δ4 desaturase. Downstream metabolism of the SAD2 reaction products would give rise to alkenes with double-bonds at position 9 or position 12, matching double-bond positions observed in alkenes in the odor bouquet of O. sphegodes. SAD1 and SAD2 show evidence of purifying selection before, and positive or relaxed purifying selection after gene duplication. By contributing to the production of species-specific alkene bouquets, SAD2 is suggested to contribute to differential pollinator attraction and reproductive isolation among these species. Taken together, these data are consistent with the hypothesis that SAD2 is a florally expressed barrier gene of large phenotypic effect and, possibly, a genic target of pollinator-mediated selection