Mahmoud Saadat

From Murmann Mixed-Signal Group

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(Research entry update on 7/31/2013)
 
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Email: mahmoud [at] stanford [dot] edu  
Email: mahmoud [at] stanford [dot] edu  
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[http://www.stanford.edu/~mahmoud/Homepage/Home.html Personal webpage]<br>  
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Conventional wireless sensor devices utilize batteries as the main power source for the sensing circuits and wireless transceiver. However, it is often desired to eliminate the battery from the system due to its limited capacity, size, cost (mainly maintenance cost), environmental impact, and operating limits. Ambient energy harvesting has found to be the most viable alternative source for low power, low data-rate wireless sensing applications, where the sensors monitor a physical quantity that changes slowly and needs to be transmitted infrequently. Depending on the application, a sensor node can harvest solar, thermal, vibrational, RF, or other forms of the ambient power.  
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Conventional wireless sensor devices utilize batteries as the main power source for the sensing circuits and wireless transceiver. However, it is often desired to eliminate the battery from a system due to its size, cost (mainly maintenance cost), environmental impact, operating limits, and limited capacity and lifetime. Ambient energy harvesting has found to be the most viable alternative source for low power, low data-rate wireless sensing applications, where the sensor monitors a physical quantity that changes slowly and needs to be transmitted infrequently. Depending on the application, a sensor node can harvest solar, thermal, vibrational, RF, or other forms of ambient energy.
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<br>This project involves design and implementation of a high performance Power Management IC (PMIC) for ambient energy harvesting. The core of the PMIC is a high-efficiency, ultra-low voltage, low-quiescent current, step-up converter which can harvest energy from one or more energy transducers and provide multiple supply rails to power the subsequent blocks and charge a temporary storage component. A power-aware analog front-end and low-power ADC are operated on a supply line from the PMIC. The sampling rate and resolution of the ADC are adaptively adjusted based on the available energy that is harvested and stored by the PMIC. Once the energy harvesting sensor platform is developed, the ambient energy transducer, micro-controller, and RF transceiver are added to create a complete energy harvesting wireless sensor node. <br><br>
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<br>This project involves design and implementation of high performance Power Management Integrated Circuits (PMIC) for ambient energy harvesting. The core of the PMIC is a high-efficiency, ultra-low voltage, low-quiescent current, DC-DC converter which can harvest energy from one or more energy transducers and provide multiple supply rails to power the subsequent blocks and charge a temporary storage component.
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[[Image:Mahmoud EnergyHarvestingSoC.JPG|left|Top Level Block Diagram of the Energy Harvesting Sensor Platform]]
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<br>The available power from energy harvesting sources can range from few micro-watts to hundreds of milli-watts and the design of a power converter to cover such a wide operating power range limits the performance. Therefore, the PMIC is split into two sub-converters: (1) a mW-converter aimed at harvesting energy from devices that generate milli-watts of power. Switching-inductor DC-DC converter is chosen here because of its high power conversion efficiency. (2) A uW-converter aimed at harvesting energy from chip-scale devices that typically generate micro-watts of power. Reconfigurable charge-pump architecture is chosen for the design of the uW-converter because it can be fully integrated (does not require any off-chip component) and have good efficiency at low power levels. The following block diagram of the PMIC illustrates both sub-converters in more details.<br>
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[[Image:Mahmoud_PMIC_BlockDiagram.jpg]]
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The current phase of this project focuses on the design of a closed-loop switched-capacitor DC-DC converter for the uW-converter section of the PMIC. The design of the uW-converter involves architecture selection for switched-capacitor power conversion stage, open-loop analysis and modeling, control design, and on-chip implementation. The following figure shows the block diagram of the uW-converter based on series-parallel charge-pump core architecture.
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[[Image:Msaadat_SPCP_closed_loop.png]]
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The first phase of the project (currently active) is the design of the power management IC. Since the available power from energy harvesting sources can range from few micro-watts to hundreds of milli-watts, design of a power converter covering the entire range leads to performance compromise. This problem can be mitigated by splitting the PMIC into two sub-converters: (1) a mW-converter aimed at harvesting energy from devices genrating milliwatts of power. A conventional switching-inductor DC-DC converter capable of harvesting energy from multiple sources is chosen primarily because of its high efficiency. (2) a uW-converter aimed at harvesting energy from chip-scale devices generating microwatts of power. A reconfigurable charge-pump architecture is chosen for the design of the uW-converter because it can be fully integrated on silicon and does not require additional off-chip component. The following block digram of the PMIC illustrates both sub-converters in more details.
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[[Image:Mahmoud PMIC BlockDiagram.jpg]]
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Latest revision as of 13:09, 31 July 2013

Mahmoud

BSEE, Sharif University of Technology, 2007
MSEE, Stanford University, 2009
Admitted to Ph.D. Candidacy: 2011-2012

Research Project: An Energy-Harvesting, Power-Aware Sensor Platform for Wireless Data Acquisition Applications

Email: mahmoud [at] stanford [dot] edu



Conventional wireless sensor devices utilize batteries as the main power source for the sensing circuits and wireless transceiver. However, it is often desired to eliminate the battery from a system due to its size, cost (mainly maintenance cost), environmental impact, operating limits, and limited capacity and lifetime. Ambient energy harvesting has found to be the most viable alternative source for low power, low data-rate wireless sensing applications, where the sensor monitors a physical quantity that changes slowly and needs to be transmitted infrequently. Depending on the application, a sensor node can harvest solar, thermal, vibrational, RF, or other forms of ambient energy.


This project involves design and implementation of high performance Power Management Integrated Circuits (PMIC) for ambient energy harvesting. The core of the PMIC is a high-efficiency, ultra-low voltage, low-quiescent current, DC-DC converter which can harvest energy from one or more energy transducers and provide multiple supply rails to power the subsequent blocks and charge a temporary storage component.


The available power from energy harvesting sources can range from few micro-watts to hundreds of milli-watts and the design of a power converter to cover such a wide operating power range limits the performance. Therefore, the PMIC is split into two sub-converters: (1) a mW-converter aimed at harvesting energy from devices that generate milli-watts of power. Switching-inductor DC-DC converter is chosen here because of its high power conversion efficiency. (2) A uW-converter aimed at harvesting energy from chip-scale devices that typically generate micro-watts of power. Reconfigurable charge-pump architecture is chosen for the design of the uW-converter because it can be fully integrated (does not require any off-chip component) and have good efficiency at low power levels. The following block diagram of the PMIC illustrates both sub-converters in more details.

Mahmoud PMIC BlockDiagram.jpg

The current phase of this project focuses on the design of a closed-loop switched-capacitor DC-DC converter for the uW-converter section of the PMIC. The design of the uW-converter involves architecture selection for switched-capacitor power conversion stage, open-loop analysis and modeling, control design, and on-chip implementation. The following figure shows the block diagram of the uW-converter based on series-parallel charge-pump core architecture.


Msaadat SPCP closed loop.png

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