USB-C does double-duty as connectivity and power management

By Maurizio Di Paolo Emilio, editor, Power Electronics News

Energy consumption is one of the biggest challenges for the mobile technology sector. USB-C was supposed to be primarily a connectivity option, but it is increasingly finding favor because it is also a useful means of managing power in portable devices.

In this ever-evolving mobile ecosystem, devices become more and more intelligent and powerful, which means that they all require more energy to work. Although manufacturers strive to reduce battery consumption, the common problem with smartphones, wearable devices, fitness bracelets, tablets, and laptops is the high energy consumption after a couple of hours of use at full capacity, necessitating a session with power supply to recharge the battery. Therefore, one of the many challenges for designers is assessing the energy factor, estimating the energy needed, and designing very efficient power management configuration.

In the design of a wireless charging system, a fundamental parameter is represented by the amount of charging power required to replenish the battery. The received power depends on innumerable factors, including the level of the transmitted power, the distance, and the alignment between the transmitting winding and the receiver, otherwise defined as “coupling” and, finally, the tolerance of the components of the transmitter and of the receiver. Nobody has time to wait for a battery to be recharged: the shorter the time to recharge the battery, the better the user experience. This is well understood in the consumer electronics market and all the major brands are trying to reduce charge times.

Devices with a USB-C port recharge quickly and offer ultra-fast transfer speeds for connection to peripherals and external devices. USB-C also supports audio and video output and is compatible with HDMI, VGA, and DisplayPort displays. USB-C is on track to become the industry standard for manufacturers of all types of devices.

But while USB-C simplifies things for end users, it increases complexity from the design and engineering point of view. There are substantial design and test challenges that designers have to face with the creation of a USB Type-C power connector that allows compatibility and reversible use with all other types. The USB port has evolved from its initial use mainly as a data interface, subsequently becoming the main means of charging portable electronic devices.

Figure 1: SM58IP04 single-chip

Silicon Mitus  has four lines of products that address the mobile device and consumer electronics market, LCD and OLED display market, and the charging accessory market. The main applications are power management integrated circuits (PMIC) for smartphone applications such as IF PMIC/Battery management with Quick charging, complete USB Type-C solutions, and wireless chargers; PMIC solutions for LCD and OLED displays for smartphones, monitors and large TVs; Audio products for boosted Class-D amplifiers, high-performance audio codec, and surface sound for flat panel displays; PMIC solutions for computing applications and USB Type-C battery chargers.

“We have shipped over 3.5 billion ICs in these markets to date.” said Youm Huh, CEO of Silicon Mitus, a South Korean company based in Pangyo (Seoul) specializing in analog IC products. “Automotive is another market we are addressing with PMIC, as well as audio products for automotive infotainment and display modules.  Silicon Mitus provides Power management IC to module manufacturers of rear-view cameras of the latest generation of cars (replacing the glass mirrors).”

Silicon Mitus recently announced the SM58IP04 : a single-chip buck-boost USB Type-C Narrow V_DC  (NVDC) charger targeting 2S/3S and 4S battery applications. It achieves up to 95% efficiency while in both buck- or boost-mode charging the battery up to 6 A due to advanced thermal management.

“We are extremely satisfied with the performances of SM58IP04: it has been quickly adopted in computing applications where the product has been very effective in delivering great performance, with a small PCB solution size and cost-saving,” said Gianfranco Scherini, the company's VP of business development. “This product combines the features of a multi-cell battery charger with the full support of the USB Type-C and PD specification.”

The USB Type-C standard meets the needs of the market in terms of power delivery and data rate, but above all, in terms of the ever-increasing quantity of devices able to interconnect. It is a reversible connector, meaning you don't need to know the connection direction. The USB Type-C standard adapts to be a perfect connection for accessories and external peripherals, but also for powering laptops and other devices.  Indeed, the USB Type-C Power Delivery (PD) standard supports currents up to 5 A and 20 V, making it possible to deliver up to 100 watts of power. Given the current levels, the standard requires appropriate protections, without which it could damage the device.

“We have proven that our strategy to push the efficiency of our buck-boost and at the same time aggressively target the highest level of integration was right.  Customers really appreciate the advantages of a simple, highly efficient solution that integrates the full support for the USB Type-C power path together with a battery charger.  With the use of the SM58IP04, each USB Type-C port behaves exactly the same and hence, it offers another level of flexibility to the system design when trying to accommodate different form factors with a common platform. We saw the potential in the USB Type-C with the release of the Power Delivery specification 3.0 and in a large amount of new use models, and this is just the beginning.  Let’s think about the capability to deliver up to 100 watts of power — 5 amp * 20 volts — with the possibility to negotiate the values of the voltages and current in any shape or form needed, ” said Scherini.

The main obstacle to implementing energy-saving solutions lies in thermal management. Technological advances in design have continually increased the need to protect components against heat build-up. For a semiconductor manufacturer, silicon packaging is a key distinguishing factor. Specifications such as thermal dissipation and overall system requirements depend largely on the packaging.

“Thermal management plays a very important role. As consumers are moving towards slimmer, fan-less notebook PCs, one of the challenges is keeping the system within a comfortable temperature to the touch and within the IC temperature range of operation,“ said Huh.

One of the critical conditions happens while the user connects the system with the power supply: in order to allow users to recharge a device in the shortest amount of time we need to pump as much power as possible into battery at once.  For example, in notebook PC and Chromebook applications it is common for the charger to deliver between 45 to 65 watts of power to the battery. This implies that with every single percentage point of efficiency loss more than half a watt is dissipated locally on the very small area of the PCB board and generates heat increasing the local temperature.

Figure 2: circuit layout for the SM58IP04 single-chip

Therefore, the hardware performance requirements address the electronics increasingly towards architectures with high-energy efficiency, so that they can support more configurations and accurate control in order to preserve the characteristics of the devices for the near future.

“SM58IP04 helps to solve this problem by addressing both the high-efficiency of the buck-boost and the optimal thermal dissipation with a package technology that maximizes the heat flow through the PCB. The higher the efficiency of the charger, the smaller the amount of power being dissipated inside the enclosure of the device, the better the heat gets dissipated thru the motherboard, the lower the temperature in the system,” said Huh.

“To support the growth in research and development, in 2017 we opened a new Design Centre in Pavia, Italy, where we find an attractive pool of skilled analog designers. We are fully equipped to deliver the latest generation of battery charger products so that our customers can take full advantage of the USB Type-C features in Mobile and Laptop applications,” said Huh.

 “That is why we decided to invest in USB Type-C battery chargers for laptop/Chromebook applications and cap dividers used in mobile applications. The output voltage of the SM58IP04 can be programmed with a granularity of 12.5 mV — fully compliant with the USB PD3.0 requiring a minimum step of 20 mV. With our product portfolio, Silicon Mitus enables new architectures for battery chargers that can bypass any internal power conversion in the device, hence eliminating the main source of power losses while keeping the current flowing into the cable within 3 A. This eliminates the need for more expensive cables, as above 3 A, the USB standard requires the use of a more expensive e-marked cable,“ Huh added.

Power management devices are increasingly smarter and more efficient. The demand for such devices is increasing rapidly due to advanced features and technology. The global PMIC market is expected to expand to a CAGR of 4.6% over the next few years and reach $ 56.48 billion by 2026.

The article  originally published at sister publication EE Times.