Polaris Semiconductor Releases Application Note Demonstrating All-Linear Li-Ion Battery Charging and Boost Solution for Noise-Sensitive Applications
Alexandria, VA – November 20, 2025 – Polaris Semiconductor LLC, developer of enhanced linear regulator (ELR) technology for noise-sensitive power management applications, today announced the release of Application Note PSAN002, "Designing a Switching-Free Boost Regulation and Battery Charging Solution for Single-Cell Li-Ion Systems."
The application note presents a complete reference design combining Polaris's BT291D50M linear boost regulator with Texas Instruments' BQ25185 linear battery charger to create an all-linear power management solution for single-cell Li-ion applications requiring clean 5V power rails. The design achieves 58-63% efficiency while maintaining completely spur-free operation—eliminating the conducted and radiated EMI associated with switching topologies.
The reference design operates from Li-ion battery voltages of 3.4-4.2V, producing a regulated 5V output suitable for powering RF front-ends, precision ADCs, sensors, and other noise-sensitive loads. The complete solution occupies just 31.8×23.4mm² on a standard 2-layer PCB and requires no inductors, significantly simplifying board layout and reducing EMC design risks.
Key Technical Achievements:
Spur-free operation: Zero switching harmonics or conducted EMI
High efficiency: 58.4% in battery-only mode, 63.3% while charging
Compact footprint: 31.8×23.4mm² total board area
Minimal BOM: No inductors or elaborate filtering required
Dual functionality: Simultaneous 5V boost regulation and 300mA battery charging
Thermal validation: Complete characterization showing package temperatures well within operating limits
The application note includes complete schematics, PCB layout files, bill of materials, and thermal imaging data from tested hardware. Engineers can use the reference design as-is or adapt it for their specific voltage and current requirements.
Target Applications:
RF transceivers and software-defined radio (SDR) systems
Medical wearables and portable diagnostic equipment
Precision sensors and instrumentation
IoT devices with strict EMC requirements
Portable test and measurement equipment
GPS receivers and positioning systems
Any battery-powered application requiring spectral cleanliness
Application Note PSAN002 is available immediately for download on our website. The BT291D50M linear boost regulator and supporting BK29 series buck regulators are available for sampling and production orders.
For technical discussions or custom voltage configurations, design engineers are encouraged to contact Polaris Semiconductor's applications engineering team.
About Polaris Semiconductor
Polaris Semiconductor designs and manufactures advanced DC voltage regulators optimized for ultra-low noise, compact integration, and high efficiency across aerospace, defense, instrumentation, and high-performance computing sectors. Based in Alexandria, VA, the company’s mission is to push the boundaries of what’s possible in analog power design.
More information: www.polarissemiconductor.com
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Photo of demonstration board associated with PSAN002.
Complete reference design is provided in the document.
