Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
08/20/10 17:21
Read: times


 		 #178157 - USB port current sourcing
Responding to: ???'s previous message
Per Westermark said:
A real USB host connector (as found on a PC) can only negotiate for up to 500mA. If the connector can supply more current or not is unknown. It may be able to supply much more. Trying to draw too much may on the other hand destroy a soldered fuse requiring the PC motherboard (or maybe PCB on the PC chassi) to be repaired. Another thing is that the original USB host connector isn't designed electrically for much more than 1A.


I learned something exciting the other day, working on a new USB audio design. I've been doing most of the testing on my recent iMac and it all works well. Then I plugged it into my old MacBook Pro (Core Duo, old!), not on battery but on the mains power, and OS X informed me that the device was drawing too much current and as such would be shut off! Obviously the laptop has a more-comprehensive port power management system than the desktop machine.

-a

List of 35 messages in thread
TopicAuthorDate
Part programmer reputation            01/01/70 00:00      
   Goals?            01/01/70 00:00      
   Why ? ? ? ? ? ? ?            01/01/70 00:00      
      "Smilies" not working            01/01/70 00:00      
         Smilies            01/01/70 00:00      
            Deep linking            01/01/70 00:00      
               I remember...            01/01/70 00:00      
      Alternative            01/01/70 00:00      
      Such as...?            01/01/70 00:00      
         Other Stuff            01/01/70 00:00      
            The things I don't have...            01/01/70 00:00      
               Some Items            01/01/70 00:00      
                  often see these referred to as "DB25" or "DB9" (sic)            01/01/70 00:00      
                     Hard to use correct terminology if people don't understand            01/01/70 00:00      
                        It's like the difference between assembler and compiler            01/01/70 00:00      
                        You can avoid the incorrect            01/01/70 00:00      
                           did you mean "without" calling it DB9?            01/01/70 00:00      
                              Yes, I did!            01/01/70 00:00      
                     Since you've done it already ... He won't            01/01/70 00:00      
   Why would you do that???            01/01/70 00:00      
   Who said that??            01/01/70 00:00      
      It's battery chargers that may have D+/D- shorted            01/01/70 00:00      
         original USB host connector isn't designed...            01/01/70 00:00      
            Most probably            01/01/70 00:00      
         USB port current sourcing            01/01/70 00:00      
            laptop has a more-comprehensive port power management            01/01/70 00:00      
   the 'reputation' of 'burners' is ....            01/01/70 00:00      
      UV light is dangerous to the eyes            01/01/70 00:00      
      EEPROMs            01/01/70 00:00      
   General response            01/01/70 00:00      
      If            01/01/70 00:00      
      Oops            01/01/70 00:00      
         I do not know what you really want            01/01/70 00:00      
            Understood            01/01/70 00:00      
               Cygnal Evaluation board            01/01/70 00:00      

Back to Subject List