Engineers that must design for very high temperature environments -- such as down-hole oil and gas, avionics, heavy industrial, and under-hood automotive -- face quite a challenge when it comes to making high precision circuits that are also reliable, compact and low power.  After all, 210°C/410°F is a great temperature to cook a pizza, but standard electronic circuits are not going to fare very well!  At these temperatures there are multiple physical phenomena working against you when it comes to the performance and reliability of integrated circuits.  and I described many of these factors in our 2012 article  "High-Temperature Electronics Pose Design and Reliability Challenges", which I would recommend reading for a good overview of the applications, challenges, solutions and best practices.

Since 2012 a lot of progress has been made in this space.  Analog Devices has released several new products for high temperature environments, enabling a signal chain for "sensor-to-bits", including sensor signal conditioning, analog-to-digital conversion and MEMS inertial sensors.  To that end, we are excited to introduce our first reference design for high temperature precision data acquisition, based around the new AD7981 High Temperature 600 kSPS SAR ADC:

In the August 2015 edition of Analog Dialogue, Maithil Pachchigar () and I present a new reference design for high temperature data acquisition, characterized from room temperature to 175°C. This circuit is intended to be a complete data acquisition circuit building block that will take an analog sensor input, condition it, and digitize it to an SPI serial data stream. It is versatile enough to be used as a single channel, or it can be scaled for multiple channel simultaneous sampling applications. Recognizing the importance of low power consumption, the power consumption of the ADC scales linearly with the sample rate. The ADC can also be directly powered from the voltage reference, eliminating the need for an additional power rail and the associated power conversion inefficiencies. This reference design is available off the shelf (CN0365) to facilitate testing by designers and includes all schematics, bill of materials, PCB artwork, and test software.  You can read the full text of the article at "A Low Power Data Acquisition Solution for High Temperature Electronics Applications"

You can see this board in action in a demo that we made that incorporates the data acquisition reference design along with the eval board for our high temp MEMS gyroscope, the ADXRS645:

For more information on high temperature products from Analog Devices, visit www.analog.com/hightemp.

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