The first part of the dissertation presents the new adapted Hall element model written
in the hardware description language Verilog-A. Verilog-A is a modeling and description
language for analog circuits. A new model makes it possible to easily change the
parameters that describe its properties depending on the technology. The model serves
as a starting point for the design of a new magnetic microsystem. The efficiency of
the simulation model is verified by the measurements of the manufactured integrated
circuits. We measured their sensitivity to external and internal magnetic fields, their
temperature sensitivity and offset voltage. In addition, we took into account the mechanical
stress which affects the magnetic sensitivity of the Hall element. The Hall
element was bonded into the ceramic package using gold wires.
In the second part of the dissertation we deal with two major disadvantages of the
magnetic microsystem based on the Hall element in CMOS (Complementary Metal
Oxide Semiconductor) technology. The first is the high power consumption and the
second is the relatively low sensitivity to the magnetic field. In general, such systems
use an array of Hall sensors to improve their efficiency, e.g. to increase the resolution
or due to the requirements of the application.
For applications that require maximum sensitivity, the array of Hall elements have
been connected directly to the power supply to ensure maximum bias current to the
sensor, thus achieving the highest possible sensitivity to the magnetic field. Conventionally,
such integrated circuits have high power consumption due to the number of
Hall elements used and their relatively low resistance.
The new method takes advantage of the ratiometric’s magnetic microsystem and
preserves its maximum sensitivity to the magnetic field. To reduce the high power
consumption, the advanced pulse-controlled Hall element bias current is used, which
reduces its effective bias current. The power consumption is reduced by a factor of 1/X
for the same sensitivity or the sensitivity is increased by a factor of X for the same power
consumption, where the factor X is defined as the ratio between the sampling period
of the Hall signal and the time when the magnetic microsystem is active and the Hall
signal measurement is performed. It has been discovered that the new method reduces
both the bias current of the Hall element and consequently the power consumption of
the magnetic microsystem. The maximum practically achievable X factor is 10.
The advanced pulse-controlled current method is implemented in the integrated
circuit manufactured in the 0.35 m CMOS technology. The efficiency of the proposed
method and the research objectives are evaluated by measuring the manufactured
integrated circuit.
|
