Sergio Morini

An offset compensation technique for bandgap voltage reference in CMOS technology

A precision integrated bandgap voltage reference in 0.35 mum CMOS technology is here presented. The circuit uses natural npn bipolar transistors as reference diodes. A particular attention was paid to the compensation of the several offsets that could strongly influence the performances of the reference. A very simple sample and hold technique for offset compensation is here presented. The proposed technique is straight forward for all bandgap topologies which use diodes with a terminal connected to the ground node or to the supply node. The temperature coefficient (TC) of the generated output voltage is 12.7 ppm/degC versus about 245 ppm/degC of the same circuit without offset compensation. A full description and an analytical expression for the proposed compensation technique are given. The results of the most relevant simulations are also reported. The circuit has been inserted in a test chip whose layout is shown.

Integrated Low-Voltage Floating Power Supply in High-Voltage Technology for High

This letter presents an integrated low-voltage floating supply in monolithic high-voltage technology aimed at supplying signal processing circuits, used in insulated-gate bipolar transistor or MOSFET-based inverter applications, diffused inside the same floating pocket where the power supply resides. This pocket is biased by the supply output with a voltage lower than the bootstrap capacitor voltage. As a consequence, signal processing circuits can be implemented using high performance, 5 V MOSFETs instead of the 20 V devices that are necessary when the bootstrap capacitor is used as a power supply. Measurements performed on a first test chip demonstrated the feasibility of the idea. The circuit was modified to make it insensitive to the charge injection phenomena caused by high dV/dt typical of these applications, as confirmed by measurements on a second test chip.

dV/dt

In this paper, an integrated solution of fault detector for motor drive applications is presented. The circuit is developed in monolithic high voltage technology. The goal of the IC is the detection of different types of fault which can affect the three phase inverter or the motor in electrical drive systems. The fault condition is detected sensing a shunt resistor put on the DC+ bus of the inverter and can be communicated to the DSP using an open drain output pin of the chip. The proposed IC represents a versatile and inexpensive solution, requires few external passive elements and can be used in applications with the inverter DC+ bus up to 600 V. The circuit does not need any external supply. It offers the possibility to regulate the voltage threshold for the fault detection using two external resistors and guarantees the response time required by the considered applications. The designed circuit, its characteristics and its performances are reported and discussed.

Applications

A monolithic over current detector for motor drive application in high voltage technology is here presented. The goal of the IC is the detection of different types of faults which can affect a triphase inverter used in motor drives applications. The over current condition is detected sensing a shunt resistor put on the DC+ bus of the inverter and is communicated to the DSP using an open drain output pin. The proposed IC represents an integrated and inexpensive solution, has a very simple structure and can be used in application with the inverter DC+ bus up to 600 V. The circuit is self-supplied and exploits the possibility to easily regulate the voltage threshold for the over current detection. The designed circuit and the most significant simulations are reported. The circuit has been diffused in a test chip: measurements demonstrates the validity of the proposed solution.

An integrated fault detector in high voltage technology for motor drive applications

This paper presents two alternative evolutions of the previous presented floating power supply in monolithic high voltage technology. These circuits are used for feeding front-end circuitry realized inside the floating pocket of a current sensor chip which transduces the phase current of a triphase AC servodrive motor. The main feature of this supply is that the floating n-epi pocket it is realized in, is biased with a voltage lower than the maximum voltage value present in the pocket itself. The presented schemes are not affected by the charge injection problem caused by high dV/dt typical of this applications. Results of the most relevant simulations are reported. The circuits have been included in two test chip whose microphotograph is shown.