Digitally Controlled, 12-V Precision Current Source for Extreme-Temperature Operation

NASA’s Jet Propulsion Laboratory, Pasadena, California

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

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