# What is the implication of supplying power the other way on this circuit?

We are having a debate on the implication of powering this circuit. The image is only a snipped of the complete hardware- but the debate arises from providing power using a PIN header connected to the +5v bus located somewhere else.

I suggested not to do this and rather connect to the usb +5/gnd pins as the +5v should be used for supply of external circuits and not really to power the entire hardware.

Will the filtering caps have any relevance if we put +5v on the +5V0 Rail instead of VBUS from the USB connector; like originally designed?

Will this circuit actually have any benefit at all?

Would powering the circuit using the TP1/2 be better than directly powering +5V bus?

-EDIT

It is not powered from a PC but a USB charger rated at 5v 1A - The device peaks 500ma~800-ma depending on what its doing. People want to connect 2A or higher to the 5v0 pin because they cannot find a USB charger with that sort of output. I am trying to establish what can happen if the +5 is connected after this circuit instead of how it was desinged.. from the USB port side.

• Related discussion that is the source of technical inquiry. This might be interesting to those that want to see more about the discussion going on, but not required reading or very pertinent here. – Kortuk Aug 16 '12 at 15:00
• To clarify a bit, are you replacing the USB power supply with a new one at the GPIO pins, or adding another power supply while the USB supply is still powered? The two answers do not make the same assumption. – W5VO Aug 16 '12 at 15:11
• The inrush current for the design shown exceeds the USB spec. You are allowed to put a maximum of 10 uF across the USB 5V supply. – markrages Aug 16 '12 at 16:34
• Why does this not mention the Raspberry Pi? – Alex Chamberlain Aug 16 '12 at 18:07
• @AlexChamberlain I think the user is asking in reference to the design of this specific circuit as best they can, no the overall product it is a part of. – Kortuk Aug 16 '12 at 18:57

Properly placed caps should be close to where they're needed. Small decoupling caps should be near the ICs that need decoupling. Your power connection should 'see' the $220 \mu F$ cap before 'seeing' the load in terms of PCB geometry, but this really depends on how the board is laid out.