24-V AC Power Stage With Wide Vin Converter and Battery Gauge Reference Design for Smart Thermostat


Design files


This reference design provides a low BOM count, high-efficiency power stage for smart thermostats and other gateway building automation designs. This power stage takes a 24-V AC input and produces a 5-V and 3.3-V output rail, which can power additional point-of-load converters if added. The design provides LiPo battery charging and seamless switching to battery power during a 24-V AC brownout. The power-path capability provides battery power assistance allowing load transient to exceed the current limit of the 24-V AC to DC system, allowing a lower cost wide-Vin buck to be used. The battery fuel gauge helps designers preserve battery life and ensure proper operation by helping the central processor make smarter decisions on power saving and system functionality.

  • Battery fuel gauge
  • Dynamic power path/battery power assist
  • High efficiency over entire load current range
  • USB overcurrent compliant
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A fully assembled board has been developed for testing and performance validation only, and is not available for sale.

Design files & products

Design files

Download ready-to-use system files to speed your design process.

TIDUCW0.PDF (5757 K)

Reference design overview and verified performance test data

TIDRQ89.PDF (617 K)

Detailed schematic diagram for design layout and components

TIDRQ90.PDF (76 K)

Complete listing of design components, reference designators, and manufacturers/part numbers

TIDRQ91.PDF (372 K)

Detailed overview of design layout for component placement

TIDRQ93.ZIP (978 K)

Files used for 3D models or 2D drawings of IC components

TIDCD95.ZIP (781 K)

Design file that contains information on physical board layer of design PCB

TIDRQ92.PDF (2114 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

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Technical documentation

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Type Title Date
* Design guide 24Vac Power Stage With Battery Fuel Gauge for Thermostat Reference Design Mar. 09, 2017
Technical article The power to innovate industrial design Mar. 27, 2017

Related design resources

Software development

BQSTUDIO Battery Management Studio (bqStudio) Software

Reference designs

TIDA-01358 24-V AC Power Stage With Wide Vin Converter and Battery Backup Reference Design for Smart Thermostat

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