“There are some not-so-great power conversion requirements at the low-to-mid end of the power spectrum, which is common in applications such as Internet of Things (IoT) devices. These applications require the use of power conversion ICs capable of handling modest current levels. The current is typically in the hundreds of milliamps range, but can be higher if the onboard power amplifier has peak power demands for data or video transmission. As a result, with the proliferation of wireless sensors supporting numerous IoT devices, there is an increasing demand for small, compact, and efficient power converters dedicated to space and thermally constrained devices.
Tony Armstrong Analog Devices
There are some not-so-great power conversion requirements at the low-to-mid end of the power spectrum, which is common in applications such as Internet of Things (IoT) devices. These applications require the use of power conversion ICs capable of handling modest current levels. The current is typically in the hundreds of milliamps range, but can be higher if the onboard power amplifier has peak power demands for data or video transmission. As a result, with the proliferation of wireless sensors supporting numerous IoT devices, there is an increasing demand for small, compact, and efficient power converters dedicated to space and thermally constrained devices.
However, unlike many other applications, many industrial and medical products typically have higher standards for reliability, size and robustness. As one might expect, a considerable part of the design burden falls on the power system and its associated supporting devices. Industrial and even medical IoT products must function properly and switch seamlessly between multiple power sources such as AC power outlets and battery backup. In addition, every effort must be made to prevent failures while maximizing operating time when powered by batteries to ensure that the system functions reliably no matter what power is present. Therefore, the power conversion architectures used inside these systems must be robust, compact, and have minimal cooling requirements.
Power Design Considerations
It is not uncommon for IIoT system designers to use linear regulators in systems that integrate wireless transmission capabilities. The main reason is its extremely low EMI and noise. Nonetheless, while switching regulators produce higher noise than linear regulators, their efficiency is far superior. Noise and EMI levels in many sensitive applications have been demonstrated to be manageable if switching regulators behave predictably. If the switching regulator switches at a constant frequency in normal mode with clean, predictable switching edges and no overshoot or high frequency ringing, then EMI will be minimal. Additionally, the small package size and high operating frequency allow for a small and compact layout, which minimizes EMI emissions. Also, if the regulator can be used with low-ESR ceramic-type capacitors, input and output voltage ripple, which is an additional source of noise in the system, can be minimized.
The main input power for today’s industrial and medical IoT devices is typically 24 V or 12 V DC from an external AC-DC adapter and/or battery pack. This voltage is then further reduced to 5 V and/or 3.x V rails by a synchronous buck converter. Nonetheless, the number of supply rails regulated internally in these medical IoT devices is increasing, while operating voltages continue to decrease. As a result, many of these systems still require 3.x V, 2.x V, or 1.x V rails to power low-power sensors, memory, microcontroller cores, I/O, and logic circuits. However, the internal power amplifier used for data transfer may require a 12 V rail with up to 0.8 A current capability to transfer any recorded data to a remote centralized hub.
Traditionally, this 12 V rail has been provided by a boost switching regulator, which requires specialized knowledge and skills in switch-mode power supply design, and occupies a considerable area on the printed circuit board (PCB).
New compact boost converter
Analog Devices’ µModule® (micromodule) products are complete system-in-package (SiP) solutions that minimize design time and address board space and density issues commonly found in industrial and medical systems. These µModule products are complete power management solutions integrating a DC-DC controller, power transistors, input and output capacitors, compensation components and inductors in a compact surface mount BGA or LGA package. Designing with ADI’s µModule products can reduce the time required to complete the design process by up to 50%, depending on the complexity of the design. The µModule family shifts the design burden of component selection, optimization and placement from the designer to the device, reducing overall design time, reducing system failures, and ultimately accelerating time to market.
In addition, Analog Devices’ µModule solutions integrate key components commonly used in discrete power, signal chain and isolation designs in a compact IC-like form factor. Backed by ADI’s rigorous testing and high-reliability processes, the µModule product family simplifies power conversion design and layout.
The µModule family of products covers a wide range of applications including termination load regulators, battery chargers, LED drivers, power system management (PMBus digitally managed power) and isolated converters. As a highly integrated solution with PCB Gerber files available for each device, µModule power products offer high efficiency, high reliability while meeting time and space constraints, and some offer low EMI per EN 55022 Class B solution.
As design resources become strained by increasing system complexity and shortening design cycles, the focus is on the development of key intellectual property in the system. This often means that power is neglected and not addressed until later in the development cycle. Due to the short time and possible limited resources for professional power supply design, it is necessary to develop high-efficiency solutions in the smallest possible size, possibly using the reverse side of the PCB to maximize space utilization.
The µModule regulator provides the ideal answer for this. The concept is complex on the inside, but simple on the outside—with the efficiency of a switching regulator and the ease of design of a linear regulator. Responsible design, PCB layout, and component selection are so important to switching regulator design that many experienced designers smell the unique scent of circuit board burning early in their careers. Off-the-shelf µModule regulators save time and reduce risk when time is short or power supply design experience is inexperienced.
A recent example of ADI’s µModule family is the LTM4661 synchronous boost µModule regulator, which is housed in a 6.25 mm x 6.25 mm x 2.42 mm BGA package. The switch controller, power FET, Inductor and all supporting components are included in the package. Operating over an input range of 1.8 V to 5.5 V, it can provide a regulated output of 2.5 V to 15 V, with the output voltage set by a single external resistor. Only one input and output bulk capacitor is required.
Figure 1.3. 3 V to 5 V input, providing up to 800 mA of 12 V with an external clock.
The LTM4661 is highly efficient, above 87% when boosted from a 3.3 V input to a 12 V output. See Figure 2 for the efficiency curve.
Figure 2. Efficiency versus output current for the LTM4661, boosted from a 3.3 V input to a 5 V to 15 V output.
Figure 3 shows the measured thermal image of the LTM4661: 3.3 V input, 12 V, 800 mA DC output, 200 LFM airflow, no heatsink.
Figure 3. Thermal image of the LTM4661: 3.3 V input, 12 V, 0.8 A output, 200 LFM airflow, no heatsink.
The deployment of IoT devices has exploded in recent years, including a variety of products for military and industrial applications. A new wave of products, including medical and scientific instruments loaded with sensors, has been an important driver of the market in recent years and is now beginning to show signs of significant growth. At the same time, the space and thermal design constraints of these systems have spawned a new class of power converters that are required to achieve the necessary performance metrics of small size, compactness, and thermal efficiency to power internal circuits such as power amplifiers. Fortunately, devices such as the recently released LTM4661 step-up µModule regulator simplify the power supply designer’s job.
Finally, it makes sense to use a µModule regulator in such applications because it can significantly reduce debug time and improve board area utilization. This will reduce infrastructure costs, as well as the total cost of ownership of the product life cycle.