The AA and AAA types of primary (non-rechargeable) battery are good enough for many applications, and they have the advantage of being both cheap and readily available. But when space is limited in a product’s enclosure, the better option is often a lithium coin cell battery such as a CR2032. Small, energy-dense sources that have low current leakage, lithium coin cells are commonly used to supply low-power IoT devices such as wireless sensors that communicate via Bluetooth®, Zigbee, NB-IoT or other wireless protocols.
IoT sensors are often not only small, but also installed in awkward locations that make battery replacement difficult. This means that battery life is a crucial design parameter for IoT device manufacturers.
The problem with primary lithium coin cells is that it is difficult to extract more than a few tens of milliwatts from a coin cell before its capacity starts to degrade and its output voltage droops: unfortunately, a wireless sensor’s RF transmissions consume hundreds of milliwatts in short bursts.
The new Nexperia NBM5100A/B and NBM7100A/B power management ICs solve the problem by saving a ‘buffer stock’ of battery energy to an external supercapacitor when the application is in a quiescent state, and then drawing energy back from it to supply a regulated output voltage capable of supporting high pulse-current loads, such as RF transmissions.
An intelligent learning algorithm monitors the energy used during repetitive load pulse cycles, and optimizes the first-stage dc-dc conversion to minimize the residual charge in the storage capacitor. The battery is never directly subjected to large pulse currents.