12 bit charge redistribution digital to analog converter for the residence time fluxgate magnetometer
The continuous advances in CMOS VLSI technology have culminated in high speed, low voltage CMOS digital circuits with gate delays below 50 ps at 1.5 V supply. At the same time, high voltage analog signal processing has fallen behind to the high flexibility and high reliability of DSP. However, the main drawback of DSP is the need for high accuracy low distortion data converters and as a consequence of the persistent efforts of reducing size, cost and power of solid-state components the field of CMOS Mixed-Signal circuit design has become of the utmost importance. The obvious functionality of data converters is to sample a signal (e.g. analog and transform it to a digital domain) and as such converters are extensively used within sensor systems to measure sound, vibration, current, voltage, magnetic field, temperature, light, imaging, acceleration and other physical quantities. A popular magnetic sensor or “magnetometer” is the fluxgate type, which uses a ferromagnetic core wounded by an excitation and a pickup coil to detect weak magnetic vector fields driven by a periodic current. A novel readout scheme currently explored at SPAWAR is represented by the Residence Times Difference (RTD) fluxgate where the detection of the magnetic field resides in time rather than in amplitude. This thesis will present a low power low distortion and high linearity Digital to Analog Converter (DAC) that can be integrated into a low power mixed-signal Application Specific Integrated Circuit (ASIC) that controls a microwire RTD fluxgate magnetometer to be used in naval operations and may be deployed to other defense markets. A new all digital switching strategy and a new common centroid layout are included. The DAC was designed and implemented in 0.35μm 4M2P CMOS technology. The main results are: chip area = 1.2 mm × 1.3 mm, power = 0.6 mW, INL = ±2 LSB, DNL = ±1 LSB, and SFDR = 84 dBc.
Alamillo, Miguel Angel, "12 bit charge redistribution digital to analog converter for the residence time fluxgate magnetometer" (2010). ETD Collection for University of Texas, El Paso. AAI1477764.