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.
In many motor and power supply applications, differential sensing of two voltages at a high common mode voltage is required. However, in a highly integrated system, high-voltage components are not always available.
A high-voltage input interface capable of sensing small differential voltages at a common mode range of 0 to 50 V across wide temperature range (–180 to +125 °C) was designed. It makes use of a standard BiCMOS (bipolar complementary metal–oxide semiconductor) process with polysilicon resistors to convert the differential voltage to current, and to subtract out the common mode. The difference current is then applied to a similar resistor and amplified.
This type of differential sensing approach has not been found in literature at the time of this reporting. Furthermore, the use of pedestrian CMOS components (standard CMOS process, polysilicon resistors) allows this design to be ported across any number of CMOS processes.
This work was done by Jeremy A. Yager of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48540
This Brief includes a Technical Support Package (TSP).
A Resistive, High-Voltage, Differential Input Interface in a 3.3-V BiCMOS 0.5-um Process for Extreme Environments
(reference NPO48540) is currently available for download from the TSP library.
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Overview
The document presents a technical overview of a resistive, high-voltage differential input interface developed at NASA's Jet Propulsion Laboratory (JPL) for use in extreme environments. The design is based on a 3.3 V BiCMOS 0.5 μm process and is particularly suited for applications that require the differential sensing of two voltages at high common mode voltages, specifically in the range of 0-50 V. This capability is essential in various motor and power supply applications where high-voltage components may not be readily available.
The interface operates through a two-phase clock system, consisting of a reset phase (φ_ZERO) and a read phase (φ_READ). During the reset phase, a switch closes to set the output to a reference voltage (V_REF), effectively removing any offset in the input stage if the input is known to be zero. In the read phase, the differential voltage is converted to current, which is then processed to produce an amplified output voltage.
Key features of the design include the use of low temperature-coefficient polysilicon resistors, which minimize variations in resistance due to temperature changes, ensuring stable performance in extreme conditions. Additionally, the operational amplifiers in the design employ biasing schemes that compensate for transistor variations with temperature, further enhancing reliability.
The research and development of this technology were conducted under a contract with NASA, highlighting its potential applications in aerospace and other fields requiring robust electronic systems capable of functioning in harsh environments. The document emphasizes the importance of this technology in advancing aerospace-related developments and its broader implications for commercial applications.
Overall, the resistive high-voltage differential input interface represents a significant advancement in electronic design, addressing the challenges of high-voltage sensing in integrated systems while maintaining performance stability across varying environmental conditions. The document serves as a technical support package, providing insights into the design, functionality, and potential applications of this innovative technology.
