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The ~98% of wasted energy makes them a very uneconomical power source. Still, they do have a place in IoT-based applications. Their relatively low initial cost makes them ideal for lower power applications. There are many different types and sizes available, and as they don’t need much additional electronics for charging or management, they are a simple solution. From a design perspective, the key challenge is making the most use out of the energy available from these little power sources. To that end, much time needs to be spent creating a power budget plan to ensure that the lifetime of the battery is maximised. For primary battery applications, two
parts from our nanopower family of products are worth considering – the LTC3337 nanopower coulomb counter and the LTC3336 nanopower buck regulator, shown in Figure 1. The LTC3336 is a low power DC-to- DC converter running from up to a 15V input with programmable peak output current level. The input can go as low as 2.5V, making it ideal for battery- powered applications. The quiescent current is exceptionally
low at 65nA while regulating with no load. As DC-to-DC converters go, this is pretty easy to set up and use in a new design. The output voltage is programmed based on how the OUT0 to OUT3 pins are strapped. The companion device to the LTC3336
is the LTC3337, a nanopower primary battery state of health monitor and coulomb counter. This is another easy device to use in a new design – simply strap the IPK pins according to the peak current required, which is in the 5mA to 100mA region. Run a few calculations based on your selected battery, then populate the recommended output cap based on the selected peak current, which is noted in the data sheet. Ultimately, this is a fantastic pairing of
devices for IoT applications with a limited power budget. These parts can both accurately monitor the energy usage from the primary battery and efficiently convert the output to a usable system voltage.
Figure 3: Charge voltage/current vs. time Figure 2: Charge current vs. battery voltage
Figure 1: LTC3337 and LTC3336 application circuit
www.electronicsworld.co.uk July/August 2022 07
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