Browsing by Subject "regulator"
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Item A capacitor-less low drop-out voltage regulator with fast transient response(Texas A&M University, 2006-04-12) Milliken, Robert JonPower management has had an ever increasing role in the present electronic industry. Battery powered and handheld applications require power management techniques to extend the life of the battery and consequently the operation life of the device. Most systems incorporate several voltage regulators which supply various subsystems and provide isolation among such subsystems. Low dropout (LDO) voltage regulators are generally used to supply low voltage, low noise analog circuitry. Each LDO regulator demands a large external capacitor, in the range of a few microfarads, to perform. These external capacitors occupy valuable board space, increase the IC pin count, and prohibit system-on-chip (SoC) solutions. The presented research provides a solution to the present bulky external capacitor LDO voltage regulators with a capacitor-less LDO architecture. The large external capacitor was completely removed and replaced with a reasonable 100pF internal output capacitor, allowing for greater power system integration for SoC applications. A new compensation scheme is presented that provides both a fast transient response and full range ac stability from a 0mA to 50mA load current. A 50mA, 2.8V, capacitor-less LDO voltage regulator was fabricated in a TSMC 0.35um CMOS technology, consuming only 65uA of ground current with a dropout voltage of 200mV. Experimental results show that the proposed capacitor-less LDO voltage regulator exceeds the current published works in both transient response and ac stability. The architecture is also less sensitive to process variation and loading conditions. Thus, the presented capacitor-less LDO voltage regulator is suitable for SoC solutions.Item An unknown regulator affects cell division and the timing of entry into stationary phase in Escherichia coli(Texas A&M University, 2005-08-29) Bain, Sherrie ValarieWhen an essential nutrient is depleted from the medium, cultures of wildtype E. coli cells enter a period called stationary phase. The transition into stationary phase is marked by distinct changes in cell physiology, gene expression, and morphology. Pr???? and Matsumura (18) found a mutant strain of E. coli that was able to continue growing exponentially at a time when wild-type cells had stopped growing and entered stationary phase. They concluded that FlhD, a transcriptional activator of flagellar genes, was responsible for this growth phenotype and that it is a regulator of cell division (17, 18). Contrary to the findings of Pr???? and Matsumura, research in our lab has shown that the mutant growth phenotype observed in the strain used by Matsumura and Pr???? is flhD independent. This study sought to identify the second mutation, which we call cdr (cell division regulator) in the strain used by Matsumura and Pr????. We used Hfr mapping and P1 transduction to localize the mutation to a specific region of the chromosome. We also sought to determine if this growth phenotype was due to loss of function or gain of function and whether the mutation in the cdr gene was sufficient to cause the observed growth phenotype in other strain backgrounds. In addition the growth phenotype of these two strains was compared to that of other wild-type and standard laboratory E. coli strains. Our results indicate that the cdr mutation is located in the 88.5. region of the chromosome and is due to loss of Cdr function. We also discovered that the growth phenotype assigned to the mutant strain more closely reflects that of other wild-type laboratory strains as did the morphology of cells in stationary phase. This evidence suggests that the actual mutant strain might be the one that was designated as the wild-type strain by Matsumura and Pr???? and both strains may contain mutations that actually cause a decrease in cell number instead of an increase as previously reported.Item Power Supply Rejection Improvement Techniques In Low Drop-Out Voltage Regulators(2011-10-21) Ganta, SaikrishnaLow drop out (LDO) voltage regulators are widely used for post regulating the switching ripples generated by the switched mode power supplies (SMPS). Due to demand for portable applications, industry is pushing for complete system on chip power management solutions. Hence, the switching frequencies of the SMPS are increasing to allow higher level of integration. Therefore, the subsequent post-regulator LDO must have good power supply rejection (PSR) up to switching frequencies of SMPS. Unfortunately, the conventional LDOs have poor PSR at high frequencies. The objective of this research is to develop novel LDO regulators that can achieve good high frequency PSR performance. In this thesis, two PSR improvement methods are presented. The first method proposes a novel power supply noise-cancelling scheme to improve the PSR of an external-capacitor LDO. The proposed power supply noise-cancelling scheme is designed using adaptive power consumption, thereby not degrading the power efficiency of the LDO. The second method proposes a feed forward ripple cancellation technique to improve the PSR of capacitor-less LDO; also a dynamically powered transient improvement scheme has been proposed. The feed forward ripple cancellation is designed by reusing the load transient improvement block, thus achieving the improvement in PSR with no additional power consumption. Both the projects have been designed in TSMC 0.18 ?m technology. The first method achieves a PSR of 66 dB up to 1 MHz where as the second method achieves a 55 dB PSR up to 1 MHz.