Spirit box multiple regulators

[Quirkey]

I'm trying to read and understand more schematics. Looking at the Spirit Box - why are there regulators for each the pt2399 and the Belton Brick when they're both L05/5V? Why not tie them to the same rail? I'm guessing there's something simple I'm missing here so I'd love to know!

 

[Robert]

Most likely to prevent noise since the Belton Brick and PT2399 are both digital.

 

[Quirkey]

Ah. Noise from the IC's or from the regulator?

 

[GAStan]

The L05/5v regulator regulates voltage at it's pin 1 to 5v REFERENCED TO PIN 2 which is typically tied to ground.

The 2933 regulator has pin 2 tied to ground so measuring it's pin 1 to ground will give 5v.. The BTDR regulator has pin 2 tied to the BTDR's pin 2, which if not at ground voltage will have the output at a different voltage than the 2399's regulator when referenced (measured) to ground. The BTDR's L05/5v will keep the voltage between it's pins 1 & 2 at 5v, pin 1 being positive. I have not seen the internal schematic of the BTDR.