Can you give the same voltage for high voltage power rail and low voltage logic power rail in a HV5308 shift register?

Question

Background info:

Hi, I am looking at a Reconfigurable Intelligent Surface (RIS) board fabricated according to the specifications in the OpenRIS project (https://github.com/jimrains/OpenRIS). In their design, they use MICROCHIP HV5308 shift registers to control the RIS elements.

My observation:

I notice in the Gerber files that the shift register's physical pin 29 and 30 are shorted, i.e., connected together:

Looking at the datasheet for MICROCHIP HV5308 (https://github.com/jimrains/OpenRIS/blob/main/hardware/datasheets/HV5308.pdf), this implies that the high voltage power rail and low voltage logic power rail are being given the same voltage supply line, which is currently about 2V. Please see image below:

My questions:

1. What is the purpose of the high voltage and low voltage power rails?
2. Is it normal to have the same voltage supply for high voltage power rail and low voltage power rail?
3. Is there a rationale behind why they are made to have the same voltage supply?

I'm a beginner in electronics, so any information at all would be helpful.

Answer 1

Take note of what it says in the table on page 9 of the data sheet: -

Let me further summarise; the lowest voltage that the HV supply can operate is 8 volts so, if you have it connected to 2 volts either there's something wrong or, the chips are intentionally disabled.

What is the purpose of the high voltage and low voltage power rails?

You can control a higher voltage with a lower voltage. A common enough thing to want.

Is it normal to have the same voltage supply for high voltage power rail and low voltage power rail?

I'm not privy to how everyone uses them but the data sheet is clear (in the table above); the lowest common recommended supply for both pins is 10.8 volts.

Is there a rationale behind why they are made to have the same voltage supply?

I'm sure there is but, without a complete tear down of the design, that's a little difficult to get to the bottom of.