Abstract

Smart meters, including gas and water meters, need to record information such as gas or water consumption and then communicate this information with a data center or end-customer. Smart meters are powered by the primary battery and need to support operation for 10 years or more. Most of the operation time is light load (about 20 uA), but during the data transmission, the load is a high pulse current load (about 250 mA). A common smart meter design challenge is supporting both high power consumption for data transmission and a long working lifetime. Some customers choose a lithium thionyl chloride (LiSOCl₂) battery to power the system because of low self-leakage current and high-power density(long lifetime). However, the LiSOCl₂ can't support high pulse current. The traditional solution is to use a LiSOCl₂ battery with a hybrid layer capacitor (HLC) package and use the HLC to support the high pulse current. But the HLC cannot control the LiSOCl₂ battery's discharge current and prevents the battery from operating at maximum capacity. Because of the HLC’s poor performance at lower temperatures, customers must choose a larger and more expensive HLC (HLC1550). This application note provides a long-lifetime and cost-competitive power solution based on the TPS61094. The TPS61094 is an ultra-low Iq (60 nA) buck/boost converter device with a supercapacitor management feature. This device allows the smart meter customers to replace the HLC with a supercapacitor to reduce the cost and also control the LiSOCl₂ battery's discharge current to extend battery life. The TPS61094 solution can increase operation time by 20%, reduce component count by 50% and decrease the total cost.