The current state of wide bandgap device technology is reviewed and its impact on power electronic system miniaturization for a wide variety of voltage levels is described. A synopsis of recent complementary technological developments in passives, integrated driver, and protection circuitry and electronic packaging are described, followed by an outline of the applications that stand to be impacted. A glimpse into the future based on the current technological trends is offered.

Wide Bandgap Technologies and Their Implications on Miniaturizing Power Electronic Systems

The present 14 V automotive electrical system will soon become 42 V. New electrical features and electrification of present mechanically driven functions will provide commercial opportunities for a new high volume application of power electronics. Cost and the thermal environment present difficult challenges to device designers. SiC is shown as a promising material for this environment. A new high efficiency power supply design using the existing automotive alternator is presented.

The future of electronics in automobiles

The need for dependable digital circuitry with the capability to operate reliably in high-temperature environments has been increasing drastically in applications such as automobile, aerospace, oil exploration, and power electronics. However, wide temperature swings significantly alter the threshold voltage of individual transistors, which adversely affects circuit timing in traditional synchronous designs. Such timing changes may in turn violates the setup and hold times of the clocked components, leading to potential circuit failure. This paper presents a complex digital integrated circuit design methodology using both synchronous and asynchronous logic for comparison in a young silicon carbide (SiC) design process developed by Raytheon UK. Seventeen circuits were designed, fabricated, and tested with results showing correct operation at temperatures at and above the target temperature of 300 °C.

Complex High-Temperature CMOS Silicon Carbide Digital Circuit Designs

The first SiC integrated circuit linear voltage regulator is reported. The voltage regulator uses a 20-V supply and generates an output of 15 V, adjustable down to 10 V. It was designed for loads of up to 2 A over a temperature range of 25-225 °C. It was, however, successfully tested up to 300 °C. The voltage regulator demonstrated load regulations of 1.49% and 9% for a 2-A load at temperatures of 25 and 300 °C, respectively. However, the load regulation is less than 2% up to 300 °C for a 1-A load. The line regulation with a 2-A load at 25 and 300 °C was 17 and 296 mV/V, respectively. The regulator was fabricated in a Cree 4H-SiC 2-μm experimental process and consists of 1000, 32/2-μm NMOS depletion MOSFETs as the pass device, an integrated error amplifier with enhancement MOSFETs, and resistor loads, and uses external feedback and compensation networks to ensure operational integrity. It was designed to be integrated with high-voltage vertical power MOSFETs on the same SiC substrate. It also serves as a guide to future attempts for voltage regulation in any type of integrated SiC circuitry.

A SiC CMOS Linear Voltage Regulator for High-Temperature Applications

This paper describes a high temperature voltage comparator and an operational amplifier (op-amp) in a 1.2- $\mu \text{m}$ silicon carbide (SiC) CMOS process. These circuits are used as building blocks for designing a high-temperature SiC low-side over current protection circuit. The over current protection circuit is used in the protection circuitry of a SiC FET gate driver in power converter applications. The op-amp and the comparator have been tested at 400 °C and 550 °C temperature, respectively. The op-amp has an input common-mode range of 0–11.2 V, a dc gain of 60 dB, a unity gain bandwidth of 2.3 MHz, and a phase margin of 48° at 400 °C. The comparator has a rise time and a fall time of 38 and 24 ns, respectively, at 550 °C. The over current protection circuit, implemented with these analog building blocks, is designed to sense a voltage across a sense resistor up to 0.5 V.

High-Temperature SiC CMOS Comparator and op-amp for Protection Circuits in Voltage Regulators and Switch-Mode Converters

In this paper, we present the design and fabrication of a high-temperature silicon carbide CMOS intelligent gate driver circuit intended for high-power switching applications. Using a temperature-insensitive comparator, several functions including overvoltage and undervoltage, as well as short- and open-load detection, are provided, all of which are operational up to 300/spl deg/C. These integrated circuits are ideally suited for harsh and high-temperature environments such as automotive and aircraft jet engines.

A silicon carbide CMOS intelligent gate driver circuit with stable operation over a wide temperature range

The design and fabrication of a high-temperature mixed-signal IC using silicon carbide CMOS technology is presented. The mixed-signal IC implements an intelligent gate driver circuit intended for high-power switching devices. Using a temperature-insensitive comparator, several functions including overvoltage, undervoltage, short-load and open-load detection are provided, all of which are operational up to 300/spl deg/C. These ICs are ideally suited for harsh, high-temperature environments such as automotive and aircraft engines.

A silicon carbide CMOS intelligent gate driver circuit

A process variation tolerant silicon carbide CMOS operational amplifier intended for high-temperature operation with a tunable phase margin and unity-gain bandwidth is presented. A novel bias circuit is provided such that the voltage gain of the operational amplifier is insensitive to large threshold voltage and mobility variations. An output stage along with an adaptive biasing technique is developed to produce a full rail-to-rail output voltage swing and a low output resistance. To achieve a large phase margin in the presence of large process variations, a compensation structure using a tunable external voltage is also proposed.

Design of a process variation tolerant CMOS opamp in 6H-SiC technology for high-temperature operation

The design and fabrication of a high-temperature mixed-signal IC using silicon carbide CMOS technology is presented. The mixed-signal IC implements an intelligent gate driver circuit intended for high-power switching devices. Using temperature-insensitive comparator, several functions including over-voltage, under-voltage, short-load and open-load detection are provided, all of which are operational up to 300/spl deg/C. These ICs are ideally suited for harsh, high-temperature environments such as automotive and aircraft engines.

High-temperature mixed-signal ICs using silicon carbide CMOS technology

A class AB silicon carbide CMOS power operational amplifier with stable open-loop voltage gain over a wide temperature range is presented. A bias circuit is provided to make the voltage gain of the operational amplifier insensitive to threshold voltage and mobility variations. A class AB output stage combined with a novel adaptive biasing scheme is developed to produce a full-rail-to-rail output swing and a low output resistance. A nested Miller compensated topology is also incorporated to provide a phase margin of 68/spl deg/. The DC gain of the operational amplifier only experiences a 0.51 dB variation over a temperature range of 25/spl deg/C to 300/spl deg/C and a 7.22 dB variation from V/sub DD/=32 V to V/sub DD/=100 V. This operational amplifier is ideal for use as a voltage buffer or power amplifier intended for high temperature operation.

Jian-Song Chen

Papers

A silicon carbide CMOS intelligent gate driver circuit with stable operation over a wide temperature range

A silicon carbide CMOS intelligent gate driver circuit

Design of a process variation tolerant CMOS opamp in 6H-SiC technology for high-temperature operation

High-temperature mixed-signal ICs using silicon carbide CMOS technology

Design of a silicon carbide CMOS power OPAMP for stable operation at elevated temperatures