2 research outputs found
A low-area reference-free power supply sensor
Power supply unpredictable uctuations jeopardize the functioning of several types of current electronic systems. This work presents a power supply sensor based on a voltage divider followed by buffer-comparator cells employing just MOSFET transistors and provides a digital output. The divider outputs are designed to change more slowly than the thresholds of the comparators, in this way the sensor is able to detect voltage droops. The sensor is implemented in a 65nm technology node occupying an area of 2700?m2 and displaying a power consumption of 50?W. It is designed to work with no voltage reference and with no clock and aiming to obtain a fast response
Voltage and capacitance sensing using time comparison
PhD ThesisWith the rapid advancement of electronic and mechanical system miniaturisation, new application
types such as portable systems, internet of things (IoT) and wireless sensor networks (WSNs)
have become promising areas of growth for industry. In these areas, the limits on battery life
have opened opportunities for energy harvesting to become a commonplace choice as the system
power source, which brings its own problems. One of these problems is that energy harvesting is
in general a much more variable energy source than batteries and mains power supply, because
of the unpredictable and intermittent nature of the external energy environment [1]. This implies
that both energy harvesters and the loads they support require significantly more control, tuning
and management than if the energy was supplied by traditional means. On the other hand,
sensing is also an important aspect for such systems as many of these systems are sensors used to
monitor physical parameters in the environment. Another reason is that the control, tuning and
management of energy harvesting requires the support of energy/power sensing. It is therefore
inevitable that sensing methods need to be developed targeting an environment where energy
supply is volatile. However, sensing under a variable energy supply faces numerous problems.
One such problem is the energy consumption of the sensing itself. In this regard, the capacitive
sensor is widely used for sensing a physical parameter, such as pressure, position, and humidity,
as it is suitable for low-power applications with limited energy budgets [2–4]. Another problem
faced by sensing under energy supply variability is the difficulty of maintaining stable voltage
and/or current references. This thesis is motivated by these issues.
In this thesis, a new sensing method is developed based on time domain techniques, which will be
shown to be 1) suitable for capacitive sensing of environmental physical parameters, 2) suitable
for sensing voltage, from which power and energy information can be derived, supporting energy
harvesting management uses, and 3) robust to voltage and power volatility, making sensors
derived from this method useful for miniaturised and energy autonomous systems.
At the centre of this work is a novel reference-free voltage level-crossing sensor, realised through
time comparison techniques. By working in the time domain, it avoids the need for voltage or
current references. Two more sophisticated sensors are then developed around this level-crossing
sensing engine. The first is a voltage monitor which is capable of sensing the crossing of multiple
predefined voltage boundaries within a range, targeting energy harvesting system management
uses. The second is a capacitance-to-digital converter which senses and converts the value of
a target capacitance to digital value. This could be used to support the monitoring of physical
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parameters in the environment including pressure, temperature, moisture, etc. as these might be
made to directly affect the values of capacitances.
This thesis describes detailed design theory and reasoning, implementation, and validation of
the presented sensors. Circuits are implemented in very-large-scale integration and investigated
in the Cadence Analog Design Environment. In addition to analogue simulations, experiments
were also conducted on a fabricated chip. Data collected from these simulation and physical
experiments show that the time-domain method developed in this work has quantitative and
qualitative advantages over existing designs