Take a fresh look at your lifestyle.

Steps to make Small Asset Tracker Last Longer

New, low-power data connections are sparking a proliferation of asset tracking solutions, thanks to their inexpensive of deployment. The results are visible in multiple applications, particularly transportation and supply chain management. Inside a typical application, a sensor provides updates from the given location, transmitting data about temperature, humidity, pressure, and motion. The sensor only must transmit small amounts of data, which results in higher coverage and ultra-low power consumption, enabling much better device longevity. The sensor's battery must last from the 3 weeks to a few years. Asset tracking, with respect to the application, may need the deployment of countless tracker devices. Accordingly, these asset tracker devices should also be small, portable, and cost effective.

In this design solution, we discuss the ability management challenges encountered with a typical battery-operated asset tracker tool and show a good example utilizing a small, high-efficiency buck converter.

Edge-to-Enterprise Communication

Figure 1 illustrates a typical tracking communication chain. The asset being tracked transmits the information via a beacon, which reaches a web server through a dedicated cellular network. From here, the data reach the enterprise portal for asset management and analytics.

Figure 1. Real-Time GPS Tracking

In the factory environment, asset tracking brings the control over facilities, vehicle fleet equipment and maintenance right into a single platform, leading to improved safety, productivity, and extended asset life.

Asset Tracking Networks

A new generation of beacons connects straight to dedicated cellular networks (LTE-M, NB-IoT), eliminating the use of Bluetooth to talk with a gateway. These technologies can be quite different but are all seen as a low-power consumption, enabling several years of battery life (Table 1).

Table 1. Networks Characteristics

NB-IoT LTE-M Units
Bandwidth 180 1400 kHz
Peak Data Rate 100 384 kbps
U/D Link Speed 62.5 1000 Mbps
Latency 10 100 ms
Battery Life >10 10 Years
Voice No Yes

 

Typical Asset Tracker System

Figure 2 shows a typical asset tracker block diagram. The three series alkaline battery supplies a control of 2000mAh. A stepdown regulator powers the on-board controller, sensors, and radio.

For demanding asset tracking applications, the machine must last for annually on 3 alkaline batteries, drawing only 100uA in deep sleep, and transmitting 100mA once each day for around 2 minutes (Figure 3). While it is true that depending on electricity and other options supported within the LTE-M or NB-IoT asset trackers, currents can be higher, for our discussion we'll keep to the 100uA to 100mA range.

Figure 3. Asset Tracker Current Profile

High-use performance requires careful selection of each block for minimum power consumption. The buck regulator should be efficient over a wide range from 100uA to 100mA. For instance, a 4% average lack of efficiency by the buck converter translates into a field deployment reduction of about two weeks.

Ultra-Low Quiescent Current

The buck converter's quiescent current is particularly important since the system is in deep sleep or quiet mode more often than not, consuming only 100uA or less. With VOUT = 1.8V, the output power during deep sleep is POUT = 1.8V × 100uA = 180uW. With η = 90%, the input power is:

pIN = 180uW/0.9 = 200uW

If the buck converter isn't carefully chosen and has an average quiescent current of 3uA and a 3.6V input voltage, there is an additional power dissipation of:

P'IN = 3uA × 3.6V = 10.8uW

The final buck converter efficiency is:

η = POUT/(PIN + P'IN) = 180/(200 +10.8) = 86% A quiescent current of 3uA robs the buck converter of 4 efficiency points draining the battery significantly faster!

On the other hand, money converter with 300nA quiescent current will barely lessen the efficiency, lowering it just half a percentage point. For asset tracking applications, it is advisable to pick a buck converter with ultra-low quiescent current because the system spends a majority of the time in “quiet” mode and uses battery.

nanoPower Buck Converter

As an example of high quality, the nanoPower ultra-low 330nA quiescent-current buck (step-down) DC-DC converter shown in Figure 4 operates from the 1.8V to five.5V input voltage and supports load currents of up to 175mA with peak efficiencies of 96%. During sleep mode, it consumes only 5nA of shutdown current. The device is housed in a space-saving 1.42mm × 0.89mm 6-pin wafer-level package (2 x 3 bumps WLP, 0.4mm pitch). If higher currents are desired based on power level in the NB-IoT or LTE-M networks, sister parts can deliver higher currents.

Figure 4. Integrated Buck Converter

Small Size

The nanoPower buck converter's application footprint is shown in Figure 5. Thanks to its WLP package, high switching frequency operation, and small external passives, the web PCB area of the buck converter is really a meager 7.1mm2.

Figure 5. Asset Tracker Buck Converter Application (7.1mm2 Net Area)

Efficiency Advantage

Figure 6 shows the efficiency curve of the buck converter having a 3.6V input and a 1.8V output. Synchronous rectification at high load and pulsed operation at light load and ultra-light load assure high efficiency across a large operating range.

An 87.5% high-efficiency operation at 100uA and 92% efficiency at 100mA helps make the IC well suited for asset tracking applications. This buck converter comes with an advantage of several efficiency points compared to alternative solutions.

Figure 6. MAX38640A Efficiency Curve

The advantages of high quality and smaller footprint work together, resulting in less heat generation. This can help in designing a smaller, cooler asset tracker, easing concerns of device overheating.

Conclusion

Asset trackers, depending on their specific application, must be employed in the area for several weeks to a few years powered only by small batteries. This type of operation requires careful choice of each block for minimum power consumption. The buck regulator must operate efficiently over a wide input current range, from many microamps to hundreds of milliamps. The MAX3864x nanoPower buck converter family, using its high efficiency and small size, provides an ideal power solution for asset tracking applications.

Courtesy: www.maximintegrated.com