Understanding the Need for Multiple VDD Groups in Microcontroller Chips
In microcontroller chips, multiple groups of VDD are often seen in the design. This design is intended to ensure power stability while reducing signal noise. This article will explore why multiple VDD groups are needed on microcontroller chips from the perspectives of internal circuit structure, power consumption, EMI/EMC, and how to design the VDD power system.01【Internal Circuit Structure of Microcontroller】To better understand why microcontroller chips have multiple groups of VDD, it is first necessary to understand the internal circuit structure of the microcontroller.Generally, the internal structure of a microcontroller can be divided into three parts: the processor core, memory, and peripherals. Among these, the processor core is an important component of the microcontroller, containing the arithmetic unit, controller, status registers, etc., used to complete various algorithms and control tasks. Memory is used to store programs and data, including flash memory, RAM, etc. Peripherals include analog interfaces, digital interfaces, timers, etc., used to connect various sensors and actuators.These parts are connected through buses, forming the internal circuit of the microcontroller. The bus includes data bus, address bus, control bus, etc., used for transferring data and control signals between various parts.In the internal circuit of the microcontroller, the power consumption of the processor core is the highest because it needs to perform various calculations and control operations. The power consumption of memory and peripherals is relatively small because they only need to store and transmit data. Therefore, when designing the VDD power system, it is necessary to optimize based on the power consumption requirements of different parts.02【Power Consumption】Within the microcontroller, the power consumption of the processor core is the highest because it needs to perform various calculations and control operations. The power consumption of the processor core mainly comes from two aspects: static power consumption and dynamic power consumption.Static power consumption refers to the power consumption of the processor core when no operations are being performed. In the circuits of the processor core, there are many static currents that consume a certain amount of power, leading to static power consumption. Static power consumption is usually related to the process technology; the smaller the process technology, the lower the static power consumption.Dynamic power consumption refers to the power consumption of the processor core when performing calculations and control operations. During calculations and control operations, the processor core needs to charge and discharge, resulting in a certain amount of dynamic power consumption. Dynamic power consumption is usually related to the frequency and voltage of the processor core; the higher the frequency and voltage, the higher the dynamic power consumption.Therefore, to reduce power consumption, it is necessary to optimize the frequency and voltage of the processor core. Generally, the voltages on microcontroller chips are fixed, such as 3.3V or 5V. Thus, to reduce power consumption, the frequency of the processor core can be adjusted for optimization.In addition to the processor core, the power consumption of memory and peripherals is relatively small because they only need to store and transmit data. However, the power consumption of memory and peripherals cannot be ignored because it affects the overall power consumption of the microcontroller system.03【EMI/EMC】In the internal circuit of the microcontroller, the transmission and processing of signals can generate electromagnetic radiation and electromagnetic interference, referred to as EMI/EMC. EMI/EMC can interfere with surrounding circuits and devices, causing system instability or failure.To reduce EMI/EMC, the VDD power system needs to be optimized. The design of the VDD power system needs to consider the following factors:Noise Filtering: The VDD power supply needs to be filtered to reduce power supply noise. Noise filtering can be achieved using ceramic capacitors, ferrite beads, and other components.Segmented Power Supply: To reduce EMI/EMC, the microcontroller chip can be divided into different areas, each using a different VDD power supply. Different areas are isolated from each other using power isolators to reduce EMI/EMC.Ground Potential: The ground potential of the VDD power supply needs to be separated from the signal ground potential to reduce interference from ground loops.04【Power Management】Power management is a very important aspect of microcontroller design. In a microcontroller system, different circuits and peripherals require different power voltages and currents. The power management system needs to control these circuits and peripherals to meet their power requirements while reducing overall system power consumption.Common power management technologies include:Power Selector: Connect different power supplies to the microcontroller system to meet the power needs of different circuits and peripherals.Power Controller: Control the power switches in the microcontroller system to turn on or off the power supply as needed, thus reducing power consumption.Power Converter: Convert the power supply voltage to the voltage required in the microcontroller system.Sleep Mode: When the microcontroller system does not need to perform calculations and control, the system can be switched to sleep mode to reduce power consumption.Power management technologies can help microcontroller systems achieve efficient power consumption management and extend system lifespan.05【Conclusion】Why are there so many groups of VDD power supplies on microcontroller chips? This is because different circuits and peripherals in the microcontroller system require different power voltages and currents. Additionally, to reduce power consumption, minimize EMI/EMC, and achieve power management, the VDD power system needs to be optimized. Optimizing the VDD power system can help microcontroller systems achieve efficient power management, reduce EMI/EMC, and extend system lifespan.Disclaimer: This article is reprinted with permission from the “Play with Microcontrollers and Embedded Systems” WeChat public account, author: Wind and Rain Unstoppable. Reprinting is for learning reference only and does not represent the views of this account. This account does not bear any copyright responsibility for its content, text, or images.END
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