Saving Space with Integrated DC-DC Converters in Distributed Power Systems

Figure 1. Compared to traditional distributed power architectures on telecom boards (left), integrated switching regulators (right) offer higher efficiency and reliability, faster design, and reduced board area.

Advantages of using integrated switching regulators

Many areas of the electronics industry, including the power electronics industry, share the goal of integrating system components to reduce overall cost, improve reliability, and minimize PCB area. Over the past two decades, power management IC manufacturers have done a lot of work to integrate many functions within the chip to meet the needs of isolated and non-isolated DC-DC conversion applications.

Integrated switching power supplies, which integrate MOSFETs, gate drivers, and PWM controllers for DC-DC switching conversion in a single package, are no longer a new concept. The challenge now is to increase the output current capability of these devices and enhance the functionality of such devices. They are well suited to the compact, multi-channel point-of-load power supplies required by distributed power in modern communications boards, providing excellent transient response to dynamic loads.

Designing, developing, and testing power supplies for communications system boards can take up a considerable amount of time in the board development process. In addition to the time spent on PCB layout, a major issue in power supply development is solving layout-related issues, including: improper power stage layout, improper grounding, placing sensitive analog traces near power lines with fast current and voltage changes, no Kelvin connection for voltage and current sensing, EMI exceeding standards, incorrect placement of decoupling capacitors, etc. When the power supply uses multiple external discrete components, these issues are most likely to cause layout errors.

In contrast, integrated switching regulators integrate the power stage (MOSFET and gate driver) and current sensing functions into the device, eliminating many PCB-related issues and thus avoiding most layout issues. In addition, the pin configuration of integrated switching regulators is also intentionally designed to avoid component placement and grounding issues. Integrated switching regulators usually provide a compact, optimized and verified PCB layout, which helps to shorten the development cycle and speed up product launch. PCB

space has become more and more tight due to the high-performance and small-size designs required in modern telecommunications system environments. Integrating the power stage and PWM controller into the chip can effectively save space; the integrated switching regulator can operate at a higher operating frequency, allowing the use of small input/output capacitors, inductors and other filter capacitors, further saving board space compared to discrete solutions. Higher operating frequencies also enable the design of wider control loop bandwidths, supporting fast load transient response.

Power conversion efficiency is an important indicator of power supply performance, which is also the main reason for replacing linear regulators with switching power supplies. Of course, switching converters will introduce higher noise and EMI. The power consumption of switching power supplies includes conduction losses (related to the MOSFET on-resistance RDS(ON)) and switching losses (related to the speed at which the MOSFET switches between the on and off states). At higher operating frequencies, switching losses dominate because the MOSFET switches on and off many times per second. The transition time depends on the impedance of the gate drive circuit, which controls the MOSFET on and off. For power supplies using discrete MOSFETs and gate drivers, the gate drive impedance is large at high frequencies due to parasitic parameters such as MOSFET pin inductance and lead inductance. Integrated switching regulators reduce parasitic components by integrating gate drivers and MOSFETs in a single package, thereby providing faster conversion times and better efficiency at high frequencies.

Thermal management is an important indicator for power supply design in large systems. In the point-of-load architecture, the heat generated by power conversion is distributed within each integrated switching regulator rather than concentrated in one power module. The higher the efficiency of the integrated switching regulator, the less heat it generates. In addition, integrated switching regulators usually use enhanced thermal packaging, solder the exposed pad directly to the PCB, and conduct heat to the ground plane through thermal vias (8mil to 12mil diameter) (the ground plane spreads the heat throughout the board, eliminating the need for a large heat sink). Finally, the thermal shutdown circuit directly controls the integrated switching power supply, which can provide effective protection in the event of overheating, preventing device damage, thereby improving system reliability.

Integrated switching regulators are available in a variety of packages and a wide range of input voltages (3V to 12V) and output currents (< 1A to 10A). The packages of low-power devices are: SOT, MSOP, and TSSOP. High-power devices are packaged in QFN, BGA and other forms, capable of dissipating high power.

Conclusion

Integrated switching regulators are ideal for medium power buses in modern telecommunication systems. Compared with regulators based on discrete MOSFETs, gate drivers and controllers, integrated solutions can greatly shorten product time to market, save space, improve efficiency, simplify system thermal management, and have higher reliability.