How to Run From a Coin Cell for 10 YearsMarch 01, 2018 by Chris Anderson
Check out this buck converter that is designed to extend battery life from months to years in IoT applications, like sensor nodes and beacons.
In this video, I have a buck converter that is designed to extend battery life from months to years in IoT applications, like sensor nodes and beacons.
The converter is ROHM’s BD70522GUL and it leverages ROHM’s proprietary Nano Energy technology, which enables an industry-leading 180 nA quiescent current and high efficiency across a wide load current range. Combining these two features with an operating voltage of 2.5 to 5.5 V makes it possible to run from various types of batteries, including coin cells, for 10 years or more.
Testing the Converter
In the video, you can see the BD70522GUL IC. It’s in a chip-scale package with a 1.76 x 1.56 mm footprint and measures just 0.57 mm thick, and you can see the total solution size is also very small, in part because of an integrated low-loss MOSFET and integrated feedback loop compensation. It also uses a 1 MHz switching frequency during constant current mode operation, which allows for smaller inductors so it can easily accommodate small design spaces.
The converter includes a 100 Ω active discharge function, power good output accurate to 5%, and two tri-state voltage select pins to set the output to 1 of 9 pre-set voltages. It uses Seamless Switching Mode Control, or SSMC, to smoothly and automatically switch conversion mode based on load current. This enables conversion efficiency above 90% from as low as 10 μA to it’s full rated output of 500 mA. In the video, I’ll show you both the low quiescent current and the efficiency across various load conditions.
Later in the video, I have the board connected to measure quiescent current, with a power supply connected to the board with a current meter inline to measure current into the IC. You can see we have 0.000xx mA, or xx nA. The 180 nA spec is, of course, a typical spec, and xx nA is still very low and is well below the max spec of 1 μA. Next, I set up and show you the wide range efficiency.
I also connect some additional meters and a load so we can see the BD70522GUL across its output range, highlighting a number of conditions across the load range and make sure everything is in line.
ROHM’s BD70522GUL provides the technology to maximize efficiency and extend battery life in IoT and other battery-power applications, with battery life of 10+ years possible thanks to its ultra-low quiescent current and high efficiency from below 10 μA up to 500 mA. For more information on ROHM’s BD70522GUL, visit ROHM's website, and be sure to check AllAboutCircuits.com for the latest news and technical resources.
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