Maxim Integrated’s Power Management Integrated Circuit (PMIC) solutions help wearable device designers achieve compact solutions with ultra-low power consumption. The high level of integration offered by the PMICs makes it possible to reduce project size by two times compared to those based on discrete components.
Any technology that allows designers to add functionality, reduce form factor, and improve power management simultaneously will find interest among developers who need to reduce the clutter of their devices to make them more attractive to end users.
Wearable Design
Designers of new wearable and connected devices are struggling to extend battery life for next-generation products—while, at the same time, increasing functionality and performance in smaller form factors (see Figure 1).
Figure 1. Wearable device for medical applications. Image courtesy of Maxim.
While the brain of the typical wearable device is the microcontroller (MCU), without forgetting the sensors, the heart of the design is undoubtedly the power management, which is essential to increasing battery life. The capacity and the size of a battery, and the working modalities of the device, are essential parameters to keep in mind during the design.
All these factors require new and innovative power management solutions to make the system work properly for wearable applications, efficiently converting the limited energy of the battery into usable energy.
The electronic design of a wearable device requires several power rails, which are traditionally made by using discrete components such as MOSFETs and transistors. Analog and power solutions for wearable devices must be highly integrated and offer low working currents. Their combination offers fully integrated PMIC solutions—with a low quiescent current that affects the ever-smaller battery to meet the wearable market’s form factor requirements. An effective system-wide approach is to divide the functional blocks to maximise the efficient use of energy (see Figure 2).
Figure 2. Block diagram for a PMIC. Image courtesy of Maxim.
A wearable device can lose its appeal if it needs to be recharged several times a day or if it has a bulky and heavy battery. Reaching work times of several days and keeping the device small and light requires careful design analysis when selecting components.
MAX20310 PMIC
Maxim Integrated’s MAX20310 power management controller with dual buck-boost SIMO architecture aims to address wearable device design issues by offering ultra-low IQ quiescent current and a single inductor layout. Essentially, it is a buck-boost switching regulator able to supply two power buses using only one single inductor. In this way, the overall dimensions are reduced, and the battery can exploit the ultra-low power management of the current with full efficiency.
The regulators are low dropout with the digital programming of the respective output voltage rails. Because the acceptable input voltage values lie between 0.7 V and 2 V, the IC can work with zinc air and silver oxide batteries, allowing the models to use primary cells instead of rechargeable cells—and thus offering an advantage for medical devices requiring sealed waterproof solutions.
This component saves energy in two ways. First, it exploits the low sleep current of the order of 600 nA per load. Second, it disconnects the loads directly when they are not active. The PMIC operates in a temperature range of -40° C to 85° C and features WLP packages with dimensions of the order of 1.63 x 1.63 mm (see Figure 3).
Figure 3. Operating circuit of the MAX20310 PMIC with MAX32620 MCU. Image courtesy of Maxim.
Considerations
As consumers demand more features in their wearable products, battery life becomes a serious problem. Along the way, wireless connectivity and integrated security will need to be supported. These trends challenge IC manufacturers to create increasingly integrated solutions with ever-lower levels of energy consumption.
When designing medical and fitness wearable applications, there are many factors to consider, including small dimensions and long battery life. Clinical environments pose additional challenges since rechargeable solutions require contacts, clips, and charging ports—where germs can accumulate.
MAX20310 proves to be a valid IC for non-rechargeable medical devices in the form of a patch, monitoring of environments and equipment, and discrete sensors for the Industrial Internet of Things (IIoT).
