Abstract:
Embedded temperature sensors based on
proportional-to-the-absolute-temperature (PTAT) current
sources have the potential to lay the foundation for low-cost
temperature-aware integrated circuit architectures if they meet
the requirements of miniaturization, fabrication process match,
and precise estimation in a wide range of temperatures. This
paper addresses an analytical approach to the minimum-element
PTAT circuit design capitalizing on the physics-based modeling
of the heterojunction bipolar transistor (HBT) structures. It is
shown that a PTAT circuit can be implemented on only two
core HBT elements with good accuracy. Derived parametric
relations allow a straightforward specification of the thermal
gain at the design stage, which affects sensor sensitivity.
Further derived current-to-temperature mapping expresses a
temperature estimate based on the measured PTAT output
current. Numerical examples indicate attainable estimation
accuracy of 0.43% in case of a measurement instance taken in
the absence of measurement noise.
