abstract: The growing demand for high performance and power hungry portable electronic devices has resulted in alarmingly serious thermal concerns in recent times. The power management system of such devices has thus become increasingly more vital. An integral component of this system is a Low-Dropout Regulator (LDO) which inherently generates a low-noise power supply. Such power supplies are crucial for noise sensitive analog blocks like analog-to-digital converters, phase locked loops, radio-frequency circuits, etc. At higher output power however, a single LDO suffers from increased heat dissipation leading to thermal issues. This research presents a novel approach to equally and accurately share a large output load current across multiple parallel LDOs to spread the dissipated heat uniformly. The proposed techniques to achieve a high load sharing accuracy of 1% include an innovative fully-integrated accurate current sensing technique based on Dynamic Element Matching and an integrator based servo loop with a low offset feedback amplifier. A novel compensation scheme based on a switched capacitor resistor is referenced to address the high 2A output current specification per LDO across an output voltage range of 1V to 3V. The presented scheme also reduces stringent requirements on off-chip board traces and number of off-chip components thereby making it suitable for portable hand-held systems. The proposed approach can theoretically be extended to any number of parallel LDOs increasing the output current range extensively. The designed load sharing LDO features fast transient response for a low quiescent current consumption of 300µA with a power-supply rejection of 60.7dB at DC. The proposed load sharing technique is verified through extensive simulations for various sources and ranges of mismatch across process, voltage and temperature. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

abstract: Modern day deep sub-micron SOC architectures often demand very low supply noise levels. As supply voltage decreases with decreasing deep sub-micron gate length, noise on the power supply starts playing a dominant role in noise-sensitive analog blocks, especially high precision ADC, PLL, and RF SOC's. Most handheld and portable applications and highly sensitive medical instrumentation circuits tend to use low noise regulators as on-chip or on board power supply. Nonlinearities associated with LNA's, mixers and oscillators up-convert low frequency noise with the signal band. Specifically, synthesizer and TCXO phase noise, LNA and mixer noise figure, and adjacent channel power ratios of the PA are heavily influenced by the supply noise and ripple. This poses a stringent requirement on a very low noise power supply with high accuracy and fast transient response. Low Dropout (LDO) regulators are preferred over switching regulators for these applications due to their attractive low noise and low ripple features. LDO's shield sensitive blocks from high frequency fluctuations on the power supply while providing high accuracy, fast response supply regulation. This research focuses on developing innovative techniques to reduce the noise of any generic wideband LDO, stable with or without load capacitor. The proposed techniques include Switched RC Filtering to reduce the Bandgap Reference noise, Current Mode Chopping to reduce the Error Amplifier noise & MOS-R based RC filter to reduce the noise due to bias current. The residual chopping ripple was reduced using a Switched Capacitor notch filter. Using these techniques, the integrated noise of a wideband LDO was brought down to 15µV in the integration band of 10Hz to 100kHz. These techniques can be integrated into any generic LDO without any significant area overhead. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2014