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VCC
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Definition: VCC stands for Voltage Common Collector. It is the positive power supply voltage for a device. In many cases, it provides the power that enables the integrated circuits (ICs), such as microcontrollers, to operate. For example, in a microcontroller circuit powered by a +5V DC supply, the VCC pin would be connected to the +5V source.
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Usage: It supplies the necessary voltage to the internal components of the microcontroller, such as the CPU core, memory, and various peripherals. The power from VCC is used to drive the transistors and other active components that perform the logical and arithmetic operations within the microcontroller.
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Typical Voltage Levels: The voltage level of VCC can vary depending on the specific microcontroller and its requirements. Common values include +3.3V, +5V, or other positive voltages. For example, in some low - power microcontrollers designed for battery - operated applications, VCC might be set to +3.3V to reduce power consumption.
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VEE
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Definition: VEE represents the negative power supply voltage. It is used in circuits that require a negative power supply, usually in more complex or specialized applications. For example, in some operational amplifier circuits that need to handle bipolar input signals (both positive and negative voltages), a negative power supply like VEE is necessary.
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Usage: In microcontrollers, VEE is not as commonly used as VCC. However, in certain analog - to - digital converter (ADC) or digital - to - analog converter (DAC) applications within the microcontroller, a negative supply voltage can be beneficial. It can expand the input or output voltage range of these converters, allowing them to handle signals that have a negative component. For example, in a precision measurement system where the input signal can swing both above and below a reference voltage, a negative supply like VEE can help in accurately digitizing the signal.
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Typical Voltage Levels: The voltage level of VEE is usually a negative value. Common values might be - 5V or - 3.3V, depending on the circuit requirements.
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VDD
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Definition: VDD stands for Voltage Drain Drain. It is also a positive power supply voltage, similar to VCC. In some contexts, VDD is used to denote the power supply for the digital part of a mixed - signal IC (which contains both digital and analog components). For example, in a microcontroller with an on - board ADC, VDD might supply power to the digital logic circuitry, while a separate power supply might be used for the analog part.
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Usage: VDD powers the digital circuits within the microcontroller, such as the digital registers, flip - flops, and other digital building blocks. It ensures that the digital signals are properly generated and processed. In some microcontrollers, VDD can also be used to power external digital components that are interfaced with the microcontroller, like digital sensors or other digital ICs.
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Typical Voltage Levels: Similar to VCC, VDD can have values like +3.3V or +5V, depending on the microcontroller's design and the overall system requirements.
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VSS
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Definition: VSS stands for Voltage Source Source. It is the ground reference voltage for a circuit. In a microcontroller, it provides a common reference point for all the other voltages (VCC, VEE, VDD). It is essential for creating a proper electrical path for the current to flow and for establishing a stable voltage reference for the internal and external components.
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Usage: All the voltages in the microcontroller are measured with respect to VSS. For example, when a digital signal transitions from a high voltage (close to VDD) to a low voltage (close to VSS), it represents a logic 0. The ground connection through VSS also helps in minimizing electrical noise and interference in the circuit. It is used as a return path for the current flowing through the various components powered by VCC and VDD.
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Typical Voltage Levels: VSS is usually set to 0V, serving as the reference ground for the entire circuit.
