The Challenges and Solutions of Powering FPGAs

　　"Many electronic engineers may not have felt the constraints of power supply on the design of FPGA, processor, ASIC, etc. urgently, but as an FPGA manufacturer, we are very clear that power supply will become more and more of a bottleneck in design," said Zhang Weichao, senior business manager of Enpirion products in ALTERA China, when talking about the challenges of power supply development. "When designing power supplies for devices such as FPGAs, engineers usually encounter many design dilemmas: market demand drives equipment manufacturers to add more and more features and functions to their products, hoping to provide greater bandwidth, further reduce the size of the package, and improve energy efficiency. The latest 28 nm and 20 nm FPGAs, processors or other SoCs all require smaller size and higher precision power management devices to support them. Most power products on the market are working hard to better solve these problems, but there are not many products that can balance multiple aspects of performance."

　　The Challenges of Powering FPGAs

　　Higher integration and power density are the inevitable trend of power supply development. With the continuous increase of system integrated functions, higher requirements are also put forward for power supply. At the same time, more modules and interfaces in the system occupy the already limited PCB board. How to reduce the power supply area and save space for the PCB board is one of the key considerations for the design of all power modules and power SoC. "Under the requirements of high integration, designers need to make trade-offs in terms of power supply anti-interference, conversion efficiency, and circuit size. We hope to have better peripheral devices, such as input and output capacitors, to eliminate ripples and provide stable current and voltage. We hope to have a higher switching conversion frequency to reduce the size of peripheral devices. Of course, the increase in frequency will affect the switching loss, causing serious heat dissipation problems for the product, thereby affecting the conversion efficiency. At the same time, many devices involve high data transmission, RF circuits (such as 4G networks), etc. These circuits are usually more sensitive to noise and require a quieter power supply design. Some engineers have to give up using switching power supplies and use inefficient linear power supplies to reduce noise interference, but this also brings about problems such as system inefficiency and heat dissipation. Similarly, when powering digital loads (FPGA core voltage, FPGA interface voltage, CPU voltage), these load voltage changes will be relatively large, and the power supply needs to have good transient performance in a short time. At present, there are high requirements for the transient effects of power supplies in the fields of industry, medical equipment, communications, etc. These are practical problems that engineers will encounter when designing power supplies." Zhang Weichao introduced, "ALTERA introduced Enpirion power supplies through acquisition this time because it is able to solve these design problems in many aspects."

　　Enpirion's three core technologies

　　According to Zhang Weichao, Enpirion's power SoC can integrate most peripheral devices into the chip, allowing the device to operate at a higher frequency and reduce switching losses. This is mainly due to three core technologies: Based on high-frequency switching IC technology, Enpirion can allow devices to operate at a higher frequency. Usually the device operating frequency is between 500kHz and 1MHz, and Enpirion can allow the device to operate at up to 5MHz. The high operating frequency allows the peripheral devices to be small, making them easy to integrate; based on the core technology of electromagnetic material engineering, power modules usually also integrate inductors, but these inductors are common products on the market. Enpirion has patented technologies for the materials and process structures of inductors, and can customize its own inductors. Integrating them into the SoC can achieve lower switching losses at higher operating frequencies, thereby maintaining good operating efficiency and achieving good EMI performance. The third core technology is its power packaging and architecture technology. When integrating power controllers, MOSFETs, inductors, compensation networks and other devices into the chip, there will be related interference or influence between the devices. How to ensure that the devices can still maintain good reliability and conversion efficiency after integration, and achieve low ripple, low noise and other performance, are further realized in the packaging architecture.

　　How to solve design problems

　　Based on the above core technologies, Enpirion can achieve high power density and small form factor packaging, which can greatly reduce the PCB area and height required for load point regulation, and the power density can be increased by 20% to 50% compared with other discrete switching regulators and modules. Through high-frequency switching technology, the device is allowed to operate at a higher frequency, which does not affect efficiency while improving integration. At the same time, with customized inductors and MOSFETs, the loop size is small and EMI can be reduced. At the same time, the EDMOS used by Enpirion is different from the industry standard MOSFET, focusing on reducing the parameters of input and output capacitors, thereby further reducing switching losses to improve efficiency. For the noise problem of switching power supplies, Enpirion can achieve switching noise close to that of linear power supplies, which can be used to power noise-sensitive circuits while ensuring conversion efficiency. Compared with power supplies composed of discrete devices, Enpirion uses a very small number of components, so it also has higher reliability. As a complete power system, Enpirion's PowerSoC has undergone special simulation tests, feature tests, verification and manufacturing tests, which can achieve 45,000 years of MTBF reliability. It is suitable for use in industries, communications, medical treatments and other fields that require high operational reliability.

　　It is reported that the new 30A all-digital PowerSoC in the Enpirion series, which is about to be launched, can achieve a conversion efficiency of more than 90% under the working environment of VIN-12 V / VOUT=1.2 V and normal temperature. It can continuously output 30A (@ 1.5V) and support parallel connection to achieve a current output of up to 180A. It is suitable for use in mid-to-high-end equipment such as communications, industry, and medical to power core processors such as FPGAs, processors, or ASICs. This product is also a fully digital Power SoC, and the control loop (Control Loop) inside the chip is also fully digital, which can realize real-time adaptive control loops, improve control accuracy, and achieve faster transient response. Its output voltage regulation accuracy is less than 0.5% accuracy (0.6V≤VOUT≤1.5V). As the core voltage of FPGAs becomes lower and lower, the current core voltage value is 2V, 1V or lower. If the power control accuracy is not enough, it is difficult to provide accurate voltage for it, and the all-digital chip can provide more precise voltage control for loads including FPGAs. At the same time, the chip can provide SmartVID and PMBus remote monitoring functions to reduce system power consumption. These two functions are widely used in mid-to-high-end equipment such as communications and industry, and can achieve more intelligent power control. The product is currently available for sampling and is expected to be mass-produced by the end of this year.

　　The PowerSoC with integrated inductor and compensation function requires simple peripheral design, which can save design time and accelerate product launch. At the same time, Enpirion will equip ALTERA's FPGA products, including the newly released MAX 10 FPGA, with power reference designs, so that customers can have the right power reference design when purchasing FPGAs, achieving a "one-stop" solution. Subsequent development requires fewer design steps, which significantly shortens the design time compared to discrete switching regulators. At the same time, these power solutions are fully verified PCB wiring and design, which can help customers succeed in the first design. The design software that comes with the solution can also facilitate engineers to easily implement the desired functions in the later design.