How much current can be drawn from USB port?

A

alphadog

Banned

• Apr 3, 2009

• #1

I'd like to connect my PCB (which has a USB Type B connector on it) to a PC.
Where can i find out how much current the USB port in PC can provide?

Thank you.

 

Mike_2545

Super Moderator

• Apr 3, 2009

• #2

I think its less that 100Ma. Somewhere around 60-70Ma. Unless you have a USB hub.

 

Last edited: Apr 3, 2009

blueroomelectronics

Well-Known Member

• Apr 3, 2009

• #3

A USB device can request up to 500mA from the host, it is normally limited to 100mA.

 

Mike_2545

Super Moderator

• Apr 3, 2009

• #4

@Blue
I remember reading something about that just recently

 

Sceadwian

Banned

• Apr 3, 2009

• #5

hubs will often further limit your current if it's a passive hub because the hub will be drawing power itself. the bulk majority of USB hubs out there today are bus powered. Only powered hubs are proof against this and even then it's up to their supply.

 

blueroomelectronics

Well-Known Member

• Apr 3, 2009

• #6

A good USB book is.
**broken link removed**

 

A

alphadog

Banned

• Apr 3, 2009

• #7

Thanks guys.
I'm going to pull maximum current of 100mA so i'm glad to here that its the limit.