Can the separate voltage outputs from the P2 distributed regulators be tied together?
VBBSim
Posts: 37
in Propeller 2
Guys I love this P2 edge concept, in fact I am changing over some of my design concepts to be inline with it.
One question I have is the understanding how important voltage levels between independent systems are.
For example, if I have a P2 on it's own power system at 3V3 and another microcontroller system on it's own regulated power system running at say 3V2 because it's under load or something or 3V4 because the regulator is slightly off.
Can I connect the P2 pins at 3V3 directly to the other systems pins at 3V2/3V4 or do I need to have a shared regulated power system or other circuit isolation such as connecting through resistors.
I noticed the output of the P2 has V00.. VN? Which are independent regulated outputs which would in theory also have slight differences in output regulation depending on load. Can these be tied together to form a single 3V3 shared output or should each subcircuit work with the independent regulated outputs or use must we use some other voltage isolation technique to connect the independent systems for example through resistors.
I would prefer not to have to isolate via resistors as there would be alot of them and selecting the correct value to cover all use cases of frequency response etc seems problematic.
Thanks
One question I have is the understanding how important voltage levels between independent systems are.
For example, if I have a P2 on it's own power system at 3V3 and another microcontroller system on it's own regulated power system running at say 3V2 because it's under load or something or 3V4 because the regulator is slightly off.
Can I connect the P2 pins at 3V3 directly to the other systems pins at 3V2/3V4 or do I need to have a shared regulated power system or other circuit isolation such as connecting through resistors.
I noticed the output of the P2 has V00.. VN? Which are independent regulated outputs which would in theory also have slight differences in output regulation depending on load. Can these be tied together to form a single 3V3 shared output or should each subcircuit work with the independent regulated outputs or use must we use some other voltage isolation technique to connect the independent systems for example through resistors.
I would prefer not to have to isolate via resistors as there would be alot of them and selecting the correct value to cover all use cases of frequency response etc seems problematic.
Thanks
Comments
A few hundred millivolts of operating difference will have no impact on digital systems.
Parallel of regulators is not practical, as the higher voltage one will try to supply all the current. The tiny P2 Eval regulators, have limited thermal capability.
Modern regulators are usually 1~2% spec'd and it would only in an Analog system that you would notice or be able to measure millivolts of difference.
If your systems can power sequence differently, you might like to have simple series protection resistors of a few hundred ohms.
In systems with differing power sources, a common problem is phantom power paths, that can provide enough current to elevate rails so reset systems are less reliable.
Voltage based POR designs are more reliable than simple RC POR for that reason.