Browsing by Subject "PSR"
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Item A Capacitor-Less Wide-Band Power Supply Rejection Low Drop-Out Voltage Regulator with Capacitance Multiplier(2014-05-22) Wang, MengdeA Low Drop-Out (LDO) voltage regulator with both capacitor-less and high power supply rejection (PSR) bandwidth attributes is highly admired for an integrated power management system of mobile electronics. The capacitor-less feature is demanded for realizing more compact device. The high PSR bandwidth is essential for being used with high frequency switching regulators. These two attributes are of strong trade-off because usually a capacitor-less LDO requires Miller Compensation which greatly limits the PSR bandwidth. This thesis presents a LDO design with both capacitor-less and high PSR bandwidth attributes. The proposed LDO structure incorporates external compensation which is gifted for extended PSR bandwidth. A capacitance multiplier (CM) of high multiplication factor (? 100) is designed to externally compensate the LDO without an external off-chip capacitor. In the proposed LDO circuit, NMOS is used as the pass transistor for system stabilization. Triple-well NMOS and Zero-Vt NMOS are used as pass transistors in the two main LDO designs. The design with the triple-well NMOS pass transistor aims at higher PSR bandwidth with lower power consumption. The design with Zero-Vt NMOS pass transistor eliminates the necessity of a charge pump for driving the gate of a NMOS pass transistor. Implemented in IBM 0.18?m technology, the LDO with triple-well NMOS achieves -40dB PSR to 19MHz with 265?A current consumption. The LDO with Zero-Vt NMOS achieves -40dB PSR to 10MHz with 350?A current consumption. In thisdesign, the feasibility of using Zero-Vt NMOS as a LDO pass transistor is proved. Moreover, compared to traditional capacitor-less LDOs with PSR bandwidth around 10kHz and above 0dB PSR beyond 10MHz, the PSR bandwidth of the proposed LDO structure is greatly extended with significant PSR over 10MHz. This also proves the feasibility of applying external compensation strategy to a capacitor-less LDO and its great beneficial effect on the PSR of the LDO.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.Item Understanding Spatio-Temporal Variability and Associated Physical Controls of Near-Surface Soil Moisture in Different Hydro-Climates(2013-05-06) Joshi, ChampaNear-surface soil moisture is a key state variable of the hydrologic cycle and plays a significant role in the global water and energy balance by affecting several hydrological, ecological, meteorological, geomorphologic, and other natural processes in the land-atmosphere continuum. Presence of soil moisture in the root zone is vital for the crop and plant life cycle. Soil moisture distribution is highly non-linear across time and space. Various geophysical factors (e.g., soil properties, topography, vegetation, and weather/climate) and their interactions control the spatio-temporal evolution of soil moisture at various scales. Understanding these interactions is crucial for the characterization of soil moisture dynamics occurring in the vadose zone. This dissertation focuses on understanding the spatio-temporal variability of near-surface soil moisture and the associated physical control(s) across varying measurement support (point-scale and passive microwave airborne/satellite remote sensing footprint-scale), spatial extents (field-, watershed-, and regional-scale), and changing hydro-climates. Various analysis techniques (e.g., time stability, geostatistics, Empirical Orthogonal Function, and Singular Value Decomposition) have been employed to characterize near-surface soil moisture variability and the role of contributing physical control(s) across space and time. Findings of this study can be helpful in several hydrological research/applications, such as, validation/calibration and downscaling of remote sensing data products, planning and designing effective soil moisture monitoring networks and field campaigns, improving performance of soil moisture retrieval algorithm, flood/drought prediction, climate forecast modeling, and agricultural management practices.