Three very-low-current analog ICs make a USB-powered thermostat

Editor’s note: Sometimes, we can get so enmeshed in complex, advanced circuit functionality that we forget that for many engineers—especially those new to the analog/power world—the basic steps of calculating component values, headroom, and levels can be a learning experience.

This design shows you how to use the standard USB port available in many portable devices to create a USB-powered fan thermostat/controller. By using a temperature sensor coupled with a simple, low-power circuit that consists of a TS6001-2.5 voltage reference, TS1001 low power operational amplifier, and TS9001 comparator, and working through the design steps and selection of component values, you’ll understand how a relatively straightforward all-analog circuit with just one sensor, a few standard-function ICs and passive components, and a MOSFET switch, is configured.

   Although the ICs called out in the schematic and BOM are from this vendor, this circuit does not rely on proprietary functions and is therefore not “restricted”—there are multiple alternate sources for these components with their basic functions.

   So, begin or resume your learning experience (or remember what you used to know, but perhaps have forgotten with the passage of time); or help guide an aspiring EE into the world of analog and power-control design and engineering with a circuit which does not require software, nor a development system, or nor expensive test equipment (a basic multimeter should do it), and has a non-critical layout. 

Click to read “Three very-low-current analog ICs make a USB-powered thermostat”, which is presented as a pdf document.

About the author

Javier Solorzano is a Senior Applications Engineer at Touchstone Semiconductor,Inc. Previously, he was in an Applications Engineering position for the High Bandwidth Product Line at Micrel, Inc. Javier earned a Bachelor of Science degree in Electrical Engineering from Santa Clara University and is currently pursuing a Master of Science degree in Electrical Engineering from Santa Clara University.

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