Innovations Embedded Switching Regulator Advances Enable Compact, Efficient Power Management Design White Paper Switching Regulators White Paper Introduction footprint constraints and component budget are Efficient power management is an important important evaluation points that should be taken in design element enabling systems developers to the first design steps. overcome increasing demands for compact size, This paper will present the benefits of incorporating low-power operation and improved functionality. a device from ROHM Semiconductor’s expanded In addition, many electronics systems require low DC-to-DC switching regulator line that delivers multiple power rails and supply solutions that need enhanced efficiency compared to competitive to address the few milliamps needed for standby and older generation voltage regulators. supplies as well as the over 100A requirements for will also illustrate how ROHM’s new switching application-specific integrated circuit (ASIC) voltage regulators enable designers to reduce the number regulators. Low-voltage processors, digital signal and size of components on the printed circuit processors (DSPs), and double data rate (DDR) board (PCB). Features of these new regulators memories also impose stringent requirements on will be discussed in detail to demonstrate their the power supply. technological advantages that include integrated Taking on these challenges, sophisticated power protection circuitry, pulse frequency modulation management technologies that make a huge (PFM), pulse width modulation (PWM), ROHM's impact to the overall solution with advances in SoftStart. Application examples where ROHM’s direct current DC-to-DC regulator technology new switching regulators are best suited will also are being adopted. In the past, designing power be presented. management has been a complicated endeavor, Power Supply Technology challenging designers new to this area. Key Portable electronic systems are pervasive in both technologies in switching mode regulators are the industrial and consumer markets. Battery- making it easier to meet these requirements powered devices, secondary point of load (POL), while delivering tremendous power savings and and distributed power supplies are a few areas that maintaining alternating current (AC) performance. regularly require power supplies. These include: To achieve the most optimum, efficient regulator It • Internet of Things (IoT) Gateways, Routers design a number of factors must be considered • Streaming Media Players, Set-Top Boxes, when selecting power management architecture HDMI Media Sticks and technology. Understanding an application’s demands such as output regulation, high operating • LCD TVs, Gaming Equipment voltage, extended temperature, and fast transient • Broadband/Communications Equipment response in terms of efficiency needed, system 2 Switching Regulators White Paper • Notebook/Tablet PCs, Servers, Printers and varying core and I/O voltages to maintain. • Storage Devices (HDDs, SSDs) The figure below illustrates the concept of a linear regulator. Consumer systems such as those listed typically use high operating voltages driven by 12-14V 2S Figure 1 and 3S battery configurations in order to achieve Linear Regulator longer battery life. Higher power applications require faster processors, which in turn necessitate larger Vout currents. And given the huge variety of components requiring power, a distributed power rchitecture is Vin commonly employed, consisting of several DC- RL to-DC power modules that convert the high bus voltage to lower supply voltage rails. However, this type of isolated configuration poses challenges As shown in Figure 1, a linear regulator is nothing more than a variable resistor whose resistance varies based on the output load resistance in order to provide a constant voltage. in meeting the requirements of many of the most common loads. Low voltage processors, DSPs, On mixed signal PCBs, the digital portion has ASICs, and DDR memories place unwavering numerous rails that can be used for components demands on the power supply to provide very fast while the analog portion has fewer. The availability transient response, high efficiency and low-voltage of multiple voltages on the digital side of a mixed rails in a compact footprint. signal circuit board allows the LDO to use a lower In many distributed power designs, a linear low supply rail to meet circuit needs. Narrowing the gap dropout (LDO) regulator is used to convert a low between the supply rail and the output as described common voltage rail down to the lower supply reduces linear loss and increases efficiency by about required for the core and input/output (I/O) voltages 50% on the digital side. Analog portions of the PCB for ICs on the PCB. The linearity in these circuits have limited supply rail options with sufficient AC will indicate the power loss experienced in the performance, which makes conversion design more conversion as well as the amount of power that difficult and demands a regulator option other than is dissipated in the LDO. For example, a common LDO. A switching regulator is a good alternative to 5V rail supplying a 3.3V to the DSP drops 1.7V in an LDO, since it inherently provides superior power the LDO, which is equivalent to a 35% power loss. savings because its efficiency is not measured by Such high loss of power leads to inefficiency that is the difference in the supply rail and output. inacceptable, especially with multiple components 3 Switching Regulators White Paper Switching Regulator Basics lossy LDO are evident in high current designs. For Transistors in a switching mode power supply example, a synchronous buck step-down supply (SMPS) operate in switching mode, as opposed with 12 Vin and 2.5 Vout loses less than 10% with a to the linear mode employed in LDOs, and can SMPS and more than 75% with an LDO. Switching be used for step-up and step-down applications. frequencies of a few kilohertz (kHz) to a few hundred With PWM implementation, a current switch with kHz are typical, with a trend toward higher frequency constant frequency and variable duty-cycle controls operation to reduce the energy per switching cycle the output of an SMPS. The semiconductor and the size of the energy storage components. transistor in the SMPS behaves like an ideal switch, Some switching regulators employ pulse width minimizing voltage drop when conducting current modulation (PWM) mode and pulse frequency (on state), and virtually eliminating current through modulation (PFM) mode control for switching based its path when not conducting (off state). Advantages on whether duty-cycle or frequency is more efficient of this low loss implementation compared to more for the application loads. Figure 2 Efficiency Curve for the BD9B300MUV (Vin = 5V, Vout = 3.3V) Newest Generation of Regulators Control over power supply implementation provides a constant switching frequency over a differentiates the newer generation of SMPS power broad range of loads - though it is more efficient regulators. Features such as PWM, PFM, protection at higher loads. Lighter loads may be better suited modes, and SoftStart reduce the complexity of for PFM control, which switches the transistors at design while increasing reliability and efficiency. varying frequencies only when required by the load PWM, the most common control for SMPS, to maximize efficiency. 4 Switching Regulators White Paper Figure 3: Switching Node and Ripple Output Waveforms for ROHM’s BD9B300MUV. VSW 2V/Div. (DC) VSW 2V/Div. (DC) VOUT 10mV/Div. (AC) VOUT 20mV/Div. (AC) Vin = 5V, Vout = 3.3V, Iout = 0A, PFM Mode Vin = 5V, Vout = 3.3V, Iout = 3A, PWM Mode Various protection modes are built into today’s Integrated Solutions Address Challenges regulators to help protect the device and act Even with these advances, switching regulators as a soft fuse, resetting when the conditions are not without challenges, including the amount that triggered them are cleared. For example, of development time devoted to testing, external overcurrent protection (OCP) ensures the chip circuitry shuts down when a load exceeds expectations. constraints, and proper board layout. Field effect Similarly, under voltage lock out (UVLO) protects transistors (FETs) are required at the voltage input the device when the input voltage falls below the and have to be carefully chosen based on the ratings, lower limit. A thermal shutdown function monitors size, configuration, and resistance characteristics the regulator die temperature and shuts down the of the application and regulator. However, ROHM chip if an environmental or other condition causes has made tremendous advancements in power it to overheat. Each of these mechanisms work management integrated circuits (ICs) to make this to protect the device and prevent damage from portion of design easier. Following the trend to common threats. ROHM developed and integrated integrate system components to maximize cost its SoftStart as a flexible feature for a variety of effectiveness, reliability, and PCB real estate, some applications that prevents harmful in-rush current at of the required DC-to-DC functional blocks such as startup. During startup, the frequency reacts to the FETs are now incorporated into ROHM’s switching voltage detected on the frequency fold back, and regulator products. the SoftStart time varies the DC-to-DC comparator output voltage based on the application's specific start conditions. 5 to support operation, PCB space Switching Regulators White Paper ON/OFF EN VCC TSD UVLO Reference REG Current Sense AMP VREF shutdown FB + 0.75V + Soft Start Error AMP OCP Σ + BST Current Comparator R S Q 800mΩ LX Oscillator 1.5MHz VOUT GND Figure 4: Block Diagram of ROHM’s BD9G101G Step-Down Switching Regulator with Built-In Power MOSFETs Perhaps the most significant challenge addressed an integrated SMPS, the parasitics and PCB trace by integrated solutions is board layout, including capacitance previously associated with the external power schemes, components is minimized, making higher switching capacitor placement, and the proximity of power frequencies and faster load-transient response and analog traces on a typical board. Integrating possible. The external capacitors, inductors, and functional blocks such as FET power staging and filters required are physically smaller, which, when current sensing reduces the number of discrete combined with the reduced number of external components required outside the regulator. ROHM components, help to minimize PCB space. An has also eliminated several PCB interconnects integrated SMPS regulator is accompanied by to reduce the likelihood of layout mistakes and tested and proven board layout guidelines that provide design freedom in component placement reduce the time spent on the design cycle and while also simplifying the grounding scheme. With layout revisions, thus speeding up time-to-market. stage layout, grounding 6 Switching Regulators White Paper Figure 5: Fast Transient Response Characteristics of ROHM’s BD9B300MUV (Vin = 5V, Vout = 3.3V, IOUT = 0A » 3A » 0A, FREQ=L, MODE=L). Applications that Can Take Advantage of Latest use in higher load applications such as industrial Switching Regulators distributed ROHM offers a comprehensive range of industrial, powered equipment. For applications with smaller consumer, battery-powered loads, including portable electronics, smartphones, equipment power supplies. The portfolio continues and universal serial bus (USB) accessories, a to grow as more compact power supply applications PFM-capable semiconductor such as ROHM’s evolve and users demand increased performance. BU90002GWZ is an optimal choice. This regulator ROHM BD9G101G DC-to-DC converter features a features an input voltage range of 4-5.5V and an wide input voltage range of 6-42V with an internal ultra-low current PFM mode to provide up to 1A load high-side 42V power MOSFET and 0.5A DC output. current. And to maximize efficiency for a range of Additional features of this PWM SMPS converter loads, the BU900002GWZ switches automatically include an extended temperature range of -40° between PFM and PWM modes based on the to +105°C, fixed 1.5MHz operating frequency, load. It also gives designers the option to override an integrated high-efficiency power block, and and force it to remain in 6 MHz PWM operation. compact form factor (SOT23 package). In addition, The feature-rich switching regulator incorporates a voltage feedback pin, along with overcurrent SoftStart and protection functions such as UVLO, protection, UVLO, and thermal shutdown are overcurrent protection, thermal shutdown and a included to ensure safety and reliability. fast transient response -- all in an ultra-compact automotive, and power, UCSP35L1 package. Given its PWM output, the BD9G101G is ideal for 7 automotive, and battery- Switching Regulators White Paper ROHM Semiconductor also offers two very of-load power supplies that can accommodate different SMPS regulators in its BD9G101G and excellent transient response to dynamic loads. BU900002GWZ models. Both products integrate Deploying ROHM SMPS Regulators protection and proprietary SoftStart functions. ROHM’s new switching regulators deliver today’s Recommended external components are listed in-demand integrated features and smaller sizes in the online datasheets, and layout support in cost-effective solutions, allowing designers is provided to ensure consistency with tested to reduce space by more than 20%. configurations. Applications with higher loads and increased power efficiency and wide voltage input high, wide voltage rails, and extended temperature capabilities, OEMs can implement reduced power requirements will find the B9G101G ideal, while the and energy saving features that improve system BU900002GWZ, which provides efficient operation reliability for a broader range of applications. In for a variety of loads, is better suited for lower addition, next-generation designs can benefit voltage, lower load applications. from noise optimization and move away from less These integrated solutions also help OEMs achieve efficient LDOs. Integrated solutions with wide design goals for greater miniaturization, cost- voltage input capabilities are able to reduce the effectiveness, improved reliability, and lower total overhead of designing external circuits to support cost of ownership required for a growing range of power supplies. Combining these advances enable applications. These make them well-suited for the efficient power management designs to finally be distributed power requirements of modern telecom within reach of even designers whose specialty is boards, which demand smaller, multiple point- the power sector. VSON008X2030 VQFN016V3030 3.0±0.1 3.0±0.1 3.0±0.1 2.0±0.1 1PIN MARK 1.0MAX 0.6MAX 1PIN MARK 0.08 S 0.08 S Figure 6: Examples of Small Packages Offered in ROHM's DCDC Switching Regulator Lineup 8 With Switching Regulators White Paper ROHM Semiconductor is an industry leader in on specific aspects of customized product system LSI, discrete components and module development. products. ROHM's proprietary production system, engineers with expertise in all aspects of design, which includes some of the most advanced development and production. This allows ROHM automation technology, is a major factor in keeping the flexibility to take on a wide range of applications it at the forefront of the electronic component and projects and the capability to serve valuable manufacturing industry. In addition to electronic clients in the automotive, telecommunication and components, ROHM has developed its own computer sectors, as well as consumer OEMs. production system which enables it to focus 9 ROHM employs highly skilled ROHM Semiconductor 2323 Owen Street Santa Clara, CA 95054 www.rohm.com | 1.888.775.ROHM NOTE: For the most current product information, contact a ROHM sales representative in your area. ROHM assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representations that the circuits are free from patent infringement. Specifications subject to change without notice for the purpose of improvement. The products listed in this catalog are designed to be used with ordinary electronic equipment or devices (such as audio visual equipment, office-automation equipment, communications devices, electrical appliances and electronic toys). Should you intend to use these products with equipment or devices which require an extremely high level of reliability and the malfunction of which would directly endanger human life (such as medical instruments, transportation equipment, aerospace machinery, nuclear-reactor controllers, fuel controllers and other safety devices), please be sure to consult with our sales representative in advance. © 2015 ROHM Semiconductor USA, LLC. Although every effort has been made to ensure accuracy, ROHM accepts no responsibility for errors or omissions. Specifications and product availability may be revised without notice. No part of this document represents an offer or contract. Industry part numbers, where specified, are given as an approximate comparative guide to circuit function only. Consult ROHM prior to use of components in safety, health or life-critical systems. All trademarks acknowledged. 1.800.775.ROHM www.rohm.com CUS15002_wp-Ver.2