The difference between the vcc/vdd/vss/vee/vbat of Stm32

Let's take a look at Stm32vet6 's pin diagram.

Circuit design and PCB fabrication, often encounter power symbols: VCC, VDD, VEE, VSS, what kind of relationship do they have?
First, explain
Vcc:c=circuit denotes the meaning of the circuit, i.e. the voltage of the access circuit
Vdd:d=device indicates the meaning of the device, that is, the operating voltage inside the device;
Vss:s=series indicates the meaning of a public connection, usually referred to as the circuit common ground terminal voltage

VEE: Negative voltage supply, field effect tube source (S)

Ii. description
1, for the digital circuit, VCC is the power supply voltage of the circuit, VDD is the operating voltage of the chip (usually VCC>VDD), the VSS is the pick-up location.
For example, for ARM microcontroller, its supply voltage VCC is generally 5 V, generally through the voltage regulator module to convert it to a microcontroller operating voltage VDD = 3.3V
2. Some ICS have both a VDD pin and a VCC pin, indicating that the device itself has a voltage conversion function.
3. In the presence effector (or COMs device), VDD is the drain, VSS is the source, and Vdd and VSS refer to the component pin, not the supply voltage.

But

1, why divide 5 to Vdd vss out?
2, which of the 5 groups of VDD VSS are responsible for the power supply of each module? Is it separate? Or are they all together?

This is related to the design of the chip. The general VDD and VSS pins are evenly distributed around the chip, and are based on power integrity considerations, which can provide the best power quality for the chip, reduce the power supply impedance, and ensure the reliable operation of high-speed digital circuits.

1, there are many functional units inside the DSP, these units need power supply, the use of multi-pin power supply can be nearby to obtain power, do not need to traverse inside.
2, different units, sometimes do not want to affect the power supply, the use of independent power supply pin, you can avoid this effect.
3, the actual use, each pin not only to connect the power supply, but also near the power supply pin to add the decoupling capacitor.
The purpose is that when the device is operating, the current changes can cause a small fluctuation in the voltage of the power supply,
Coupled with the decoupling capacitor, this fluctuation is not easily transmitted to another power supply pin.

About Vbat:

When a battery or other power is connected to the Vbat pin, the contents of the backup register and the ability to maintain the RTC can be saved when VDD is powered off.

If no external battery is used in the application, the Vbat pin should be attached to the VDD pin.

The difference between the vcc/vdd/vss/vee/vbat of Stm32