Step-down DC/DC converters (see Figure 1) are a very popular switching DC/DC regulator topology that is widely used in many electrical and electronic applications, from cloud infrastructure to personal electronics to factories and buildings. automation. They account for more than 75% of all non-isolated switching regulator topologies today.
The layout of the buck converter is just as important as the simulation and design, but lack of good layout practices can delay development time and even cause operational and reliability issues.
Layout considerations include bypass capacitors, feedback compensation network components, power components, parasitic components, ground loops, and connections.
Bypass capacitor
For bypass capacitors, it is important to minimize lead inductance by reducing the bypass loop area, shortening the length on the high di / dt (current slew rate) path, using the ground plane whenever possible (if possible), at both ends of the capacitor It is implemented by introducing a current path and avoiding multiple layouts. In addition, it is important to parallel different capacitor types to reduce the impedance across the capacitive band because it can reduce the impedance in the 2MHz to 20MHz frequency range (typical capacitor values ​​from 0.1μF to 0.01μF). Traction capacitors, bringing them closer to the integrated circuit (IC) pins, can also show the layout designer the critical nodes and areas, as shown in Figure 2.
Feedback compensation network
Place the compensation network close to the IC error amplifier. Place the resistors so that they are connected directly to the inverting input of the error amplifier (FB pin) as shown in Figure 3.
Power component
Make sure the power components are properly connected because of the high di / dt (current slew rate) in the current path, as shown in Figure 4. Any inductance in the path will cause the switching node to ring, which may exceed the absolute maximum rating of the power FET and will also generate harmonics and unwanted noise in the system. The goal is to minimize loop area by using an assembly of a double-sided printed circuit board (PCB) with a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) on one side of the PCB and a capacitor on the other side. Make sure the components are placed and laid out correctly. The correct design eliminates the need for snubber circuits to reduce switching node ringing.
Parasitic component
Pay attention to parasitic components as they may introduce and increase the impedance in the power supply, which can cause stability and operational problems. Pay attention to wiring inductance, especially low impedance circuits and filters, power switches and timing circuits. Use ground planes and wide traces to minimize inductance. Pay attention to high-impedance or noise-sensitive circuits in terms of board capacitance, and pay attention to the coupling between board plane/layer and component pads. Magnetic coupling may also occur between inductors, especially toroidal inductors. In this case, please consider other installation directions. Magnetic coupling can also occur between loops, so the loop area should be minimized and the ground plane used.
Ground loop and connection
A better approach is to use multiple points of grounding. As shown in Figure 6, multi-point grounding allows for low impedance between the circuits to minimize potential differences and also reduces circuit trace inductance. The goal is to include high frequency current in a single circuit and keep it out of the ground plane.
Many buck converter control ICs recognize noise and quiet circuit areas, and the IC pins are arranged in such a way that layout and component placement around the IC pins is easier. Some even provide separate pins for power and analog ground, as shown in Figure 7 for the TPS40170 60V Synchronous Buck Pulse Width Modulation (PWM) controller pin.
Therefore, layout planning around the IC pin layout and using the layout practices mentioned in this article can help you get the right buck converter design from the start and avoid any trouble later. Check TI's Buck Converter and Buck Controller Selection Chart for a variety of step-down DC/DC solutions.
best dc current sensor,best current sensor,ac current sensor,battery current sensor
Shanghai Zhilong Electronic Technology Co.,Ltd , https://www.zhilongsensor.com