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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This article first appeared in the February, 2015 issue of NASA Tech Briefs Magazine.

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