Weak current College】 【VCC, VDD and VSS three grade difference】.

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In the electronic circuit, often you can see the VCC, VDD and VSS three different symbols, what is the difference between them?

I. interpretation
VCC: C = meaning of microcircuit circuit, namely, the access circuit voltage;
VDD: D = device represents the devices meant that the device's internal operating voltage;
VSS: S = series represents the public connection, usually refers to the common grounding Terminal voltage circuits.

II. Description
1, for digital circuits, VCC power supply voltage of the circuit, VDD is chip voltage (typically Vcc > Vdd), VSS is received. (For example, for the ARM microcontroller circuit, the power supply voltage VCC is 5V, generally after three-voltage block it into microcontroller operating voltage VDD = 3.3V)
2. some IC with VDD pin and the VCC PIN to demonstrate this device itself with voltage conversion function.
3, the presence of effects tube (or COMS devices), VDD, VSS for drain as source, VDD and VSS refers to the symbol pin and does not represent a supply voltage.