Intelligent battery life booster IC makes powering the IoT leaner and greener

Introduction

As Internet-of-Things (IoT) technology reduces form factor and power consumption, many new battery-powered applications have become possible. For example, the wireless readings from remotely located ‘smart-agriculture’ soil moisture sensors are helping farmers to increase yields and make their farms more environmentally friendly. In sprawling storage facilities, wireless sensors send periodic temperature measurements, helping warehouse operators maintain operating conditions suitable for the types of goods being stored there. While these innovations are valuable, the very feature enabling their operation is also their biggest shortcoming – battery power. Without it, locating sensors at geographically remote locations would be impossible because no alternative fixed power source is typically available and installing one would be prohibitively expensive. In this blog, we show how IoT device operation can harm battery capacity before presenting a pioneering IC Nexperia has developed to boost battery life, so they need replacing much less often.

Pulsed operation pulls down battery voltage

Environmental variables like temperature, pressure and humidity typically change very slowly, so they don’t require measuring very often – perhaps only once every few hours. Similarly, many security cameras only need to capture and transmit a video signal if they detect movement at the location they are monitoring. Therefore, these devices can spend most of their working life on standby or sleep mode, only waking periodically to record and transmit a reading or video stream. In addition, long periods in sleep mode help conserve power (consuming only a few microamps), and they can operate off Lithium primary coin cell batteries (like CR2032) or lithium thionyl chloride (like LS14250) for several years. Non-rechargeable lithium primary batteries have high energy density and long shelf life.

Sleep mode is not an issue for lithium primary batteries. However, the infrequent periodic short bursts of activity (pulsed mode) when the device’s microcontroller, sensor and wireless radio (LoRa, Wi-Fi, Zigbee) are all fully powered up is problematic. Lasting only a few milliseconds, these bursts consume 10s to 100s of milliamps, significantly straining a coin cell battery. Coin cell manufacturers rate these product lifetimes for relatively low standard current draws (<1-3 mA). Extended use in this brief, high-current pulsed mode is detrimental to overall cell capacity (lifetime) while simultaneously causing a significant drop in voltage during heavy loading—potentially making it too low for the application it is powering.

Intelligent battery booster IC maintains a constant voltage level

Nexperia’s NBM7100A/B and NBM5100A/B are revolutionary new battery management ICs that can extend the life of a typical Lithium coin cell battery by up to an order of magnitude (10x) while increasing the peak output current available to a pulse load by up to 25x. These ICs contain two high-efficiency DC/DC conversion stages and an intelligent learning algorithm. The first conversion stage transfers energy from the battery to a capacitive storage element at a low rate. The second stage utilizes the stored energy to provide a regulated (programmable from 1.8 V to 3.6 V) high pulse (up to 200 mA) current output. The intelligent learning algorithm monitors the energy used during repetitive load pulse cycles and optimizes first-stage DC-DC conversion to minimize the residual charge in the storage capacitor. When not performing an energy conversion cycle (standby state), these devices consume less than 50 nA.