About powered by USB

[Jeckson]

Hai
Great Sonsivri.

How much current could drive from USB port?
Kindly advice to avoid damaged the usb port..if I'm not wrong the Voltage around 5 VDC and 4 VDC.

Regards
Jeckson

[mmladenovic]

Hi,
500mA (2.5W) MAX

Regarsd
Milan

[lm317]

USB1.1 and usb2.0 port can provide  max 500mA current . But several laptops 100mA max.  

if your  usb device wants more current, laptop may  provide current up to 500mA. More current request should via usb descriptors.

[pickit2]

On some MotherBoards limit to 100mA and by request can call upto to the 500mA.

[Jeckson]

Thank you

100mA as safety

0.1x5 VDC= 0.5 W

Thank's

Posted on: January 02, 2010, 01:26:35 13:26 - Automerged
Thank's

I forgot....

When we have 4 ports meant 4x 100mA? or just 100mA in total
or when have 2 usb ports then means 2 x 100mA? or just only 100mA in total

Whats the meaning of

>by request can call upto to the 500mA.

>if your  usb device wants more current, laptop may  provide current up to 500mA. More >current request should via usb descriptors.

Did I modified from manufacture schematics?

Regards
Jeckson

[frasenci]

 
This one has always puzled me. Some time ago I did a little research on the matter with no outcome at all. An USB powered external USB HDD would not power up when connecting to an notebooks USB port. Wheras it run smoothly from a Desktop. I kicked the same walls here and there and finally opted to external-power it with an AC adapter. On that event I was told to look in Control Panel and see the current reported by the HUB...

Just want to document some more in hope somebody "hardware inclined" can give us all a good explanation.
I am attaching picture with XP reporting 100 mA current for an wireless mouse and 2 mA, that is right, only 2 mA for an external 320 Gb USB SATA HDD while it is being defragmented. I do not believe what the OS is reporting.
In This same Notebook now, I have connected 3 USB HDD simultaneously + Wireless mouse just to test, all running smoothly.

I really do not think it is Descriptor side fixed because the same drive that reports 2 mA here, will not power up on my USB enabled DVD player at home ( must use AC adapter ).
It is somehow, misteriously driven from the motherboard side, whatever.

Interesting if someone can dig more in this topic. Thank you.

Greetings
Francisco

[pickit2]

really do not think it is Descriptor side fixed because the same drive that reports 2 mA here, will not power up on my USB enabled DVD player at home ( must use AC adapter ).
It is somehow, misteriously driven from the motherboard side, whatever.

It is the usb device that calls for power, your DVD knows it is to be powered from external power, it don't call for any power from the usb port.
Well the history of usb ports on older mother boards, was just that, 2 ports at 100mA each, so when you connect a usb device the device take upto 100mA and if it needs more it will call for up to 500mA, before needing to be powered from external supply.
On the newer mother boards, they added 2xhubs, so they will supply upto 500mA each port, to give a total of upto 4Amp (Load no problem for a desktop pc). 
Thats why you get a lot of people give the wrong advise, to use a external hub, to solve driver problems.
There is a lot of examples to look at, from the way microchip use usb (see thier vast collection of Application Notes, also the info for the pickit2 has lots of info on the usb control, as to use usb power or from the device being programed)

[Jeckson]

PICKIT and franseci

Is from 100mA to 500mA by software or "automatically increased"?

Regards
Jeckson

[tAhm1D]

Hi,
Usually specifications for USB power are 5v, 500mA, which is provided by all desktops. Some laptops, however cannot provide that much current. But, I guess more than 300mA shouldn't be used from USB, in that case, use an external power supply as it is safer and may prevent damage to your motherboard.
I have a USB powered HDD (external) which requires about 400mA. But I saw some with requirements of 800mA, which are connected to 2 USB ports at the same time. I am not sure, but probably, each USB port can provide 500mA max.

[Jeckson]

Hai

I just got 100 mA max.
Thought that 100mA is the safe.

Regards
Jeckson

[aj49m]

On some MotherBoards limit to 100mA and by request can call upto to the 500mA.

exactly, first there is that investigate power capacity PC host usb, and after, configure descriptor of USB device to rise the current.

500mA is maximun, but is not recommended