In microcontroller chips, multiple groups of VDD designs are often seen. 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.
1. Internal Circuit Structure of Microcontrollers
To better understand why there are multiple groups of VDD on microcontroller chips, it is first necessary to understand the internal circuit structure of microcontrollers.
Generally, the internal structure of a microcontroller is divided into three parts: the processor core, memory, and peripherals.
Among them, the processor core is an important component of the microcontroller, containing the arithmetic unit, controller, status registers, etc., used to perform 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., to connect various sensors and actuators.
These parts are connected by a bus, forming the internal circuit of the microcontroller. The bus includes data bus, address bus, control bus, etc., used for transmitting data and control signals between various parts.
In the internal circuit of the microcontroller, the processor core consumes the most power because it needs to perform various computation and control operations. The power consumption of memory and peripherals is relatively small, as they only need to store and transmit data. Therefore, when designing the VDD power system, it is necessary to optimize according to the power consumption needs of different parts.
In the microcontroller, the processor core has the highest power consumption because it needs to perform various computation and control operations. The power consumption of the processor core mainly comes from two aspects: static power and dynamic power.
Static power refers to the power consumed by 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, thus generating static power. Static power is usually related to the process technology; the smaller the process technology, the lower the static power.
Dynamic power refers to the power consumed by the processor core when performing computation and control operations. During computation and control operations, the processor core needs to charge and discharge, resulting in a certain amount of dynamic power. Dynamic power is usually related to the frequency and voltage of the processor core; the higher the frequency and voltage, the higher the dynamic power.
Therefore, to reduce power consumption, it is necessary to optimize the frequency and voltage of the processor core. Generally, the voltage on microcontroller chips is fixed, such as 3.3V or 5V. Thus, to reduce power consumption, the frequency of the processor core can be adjusted for optimization.
Besides 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, as it will affect the overall power consumption of the microcontroller system.
In the internal circuit of the microcontroller, the transmission and processing of signals can produce electromagnetic radiation and electromagnetic interference, referred to as EMI/EMC. EMI/EMC can interfere with surrounding circuits and devices, leading to system instability or failure.
To reduce EMI/EMC, it is necessary to optimize the VDD power system. The design of the VDD power system needs to consider the following factors:
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Noise filtering: The VDD power supply needs to be filtered to reduce power noise. Noise filtering can be achieved using ceramic capacitors, ferrite beads, and other components.
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Segmented power supply: To reduce EMI/EMC, the microcontroller chip can be divided into different areas, each using a different VDD power supply. Isolation devices can be used to isolate different areas to reduce EMI/EMC.
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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.
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 system power consumption.
Common power management techniques include:
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Power selector: Connect different power supplies to the microcontroller system to meet the power needs of different circuits and peripherals.
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Power controller: Control the power switches in the microcontroller system to turn on or off the power as needed, thereby reducing power consumption.
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Power converter: Convert the power supply voltage to the voltage required in the microcontroller system.
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Sleep mode: When the microcontroller system does not need to perform computation and control, it can switch the system to sleep mode to reduce power consumption.
In summary, power management technology can help microcontroller systems achieve efficient power management and extend system life.
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, and to reduce power consumption, reduce 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 life.
Source: Mastering Microcontrollers and Embedded Systems
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