Many control applications require precision, high-voltage-capable stimulus current drivers for sensor excitation. In particular, a requirement for a stimulus driver that can be primarily integrated into a motor feedback signal conditioning ASIC (application specific integrated circuit) for Martian environments is satisfied by this development.
Wide-temperature and extreme-environment electronics are crucial to future missions. These missions will not have the weight and power budget for heavy harnesses and large, inefficient warm boxes. In addition, extreme-environment electronics, by their inherent nature, allow operation next to sensors in the ambient environment, reducing noise and improving precision over the warm-box-based systems employed today.
A system that allows the driving of a regulated current from a 12-V supply into a sensor bridge from 0 to 9 V is disclosed. This current source is designed to operate from –180 to +125 °C, in keeping with specifications for operation in lunar and Martian environments.
The basic function of this circuit is that of a current regulator that sets the voltage across an off-chip control resistor, thus setting the current into the sensor bridge. The off-chip resistor is chosen at design time to set the current range and precision required by the application. During operation, the user may modulate the DAC voltage to produce a similarly modulated bridge current for AC-type bridge applications.
This process allows this device to be included in system-on-chip implementations where high-voltage devices are not readily available. Extreme-environment electronics are valuable to a number of disciplines, including military/aerospace, automotive, scientific research, and energy.
This work was done by Jeremy A Yager, Tuan A. Vo, and Mohammad Mojarradi of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48537
This Brief includes a Technical Support Package (TSP).
Digitally Controlled, 12-V Precision Current Source for Extreme-Temperature Operation
(reference NPO-48537) is currently available for download from the TSP library.
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Overview
The document discusses a Digitally Controlled 12-V Precision Current Source developed by researchers at NASA's Jet Propulsion Laboratory (JPL) for extreme-temperature operation. This technology is particularly relevant for applications requiring precise, high-voltage capable stimulus current drivers for sensor excitation, especially in the harsh environments of lunar and Martian missions.
The current source is designed to operate within a voltage range of 0-9 V, powered by a 12 V supply, and is capable of functioning across a wide temperature spectrum from -180°C to +125°C. This capability is crucial for space exploration, where equipment must endure extreme conditions. The design incorporates advanced components, including high-voltage N- well and NMOS transistors, which can withstand drain-source and N-well breakdown voltages exceeding 60 V. The absence of a PMOS high-voltage transistor in the process necessitated a PMOS cascode structure, which is supported by a dedicated bias circuit to ensure proper operation.
The document highlights the circuit's basic function as a current regulator that sets the voltage across a resistor (R_SET), thereby controlling the current flowing into the sensor bridge. This design allows for modulation of the Digital-to-Analog Converter (DAC) voltage, enabling the production of a modulated bridge current suitable for AC-type bridge applications, with a modulation frequency capability of up to 5 kHz.
To ensure reliable operation across extreme temperatures, the design employs SiGe NPN transistors, which offer significant advantages over standard silicon bipolar transistors. Additionally, the amplifier and DAC designs utilize techniques such as constant-gm current biasing and Minch cascode biasing to maintain performance across the specified temperature range.
The document serves as a technical support package, providing insights into the development and capabilities of this precision current source. It emphasizes the importance of this technology in advancing aerospace applications and highlights the collaborative efforts of JPL and NASA in pushing the boundaries of engineering and technology for space exploration.
Overall, this precision current source represents a significant advancement in the field, enabling more reliable and effective sensor operations in extreme environments, thereby contributing to the success of future space missions.
