If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
USB MP3 battry question
If I have a usb mp3 connected by a usb cable and the pc is in standby mode
or is totaly off will the pc drain the mp3 players battry? Thanks GK |
#2
|
|||
|
|||
USB MP3 battry question
Gabriel Knight wrote:
If I have a usb mp3 connected by a usb cable and the pc is in standby mode or is totaly off will the pc drain the mp3 players battry? Thanks GK There is no way to know that for certain. It might depend on the cheapness of the design. The first item I got in a search, was an EDN article. This is a picture from the article. http://www.edn.com/contents/images/185954f1.pdf That shows three circuits total. First circuit, with the MAX1811, converts Vusb to Vlithium_battery. The other two, derive operating voltages later, for operating logic ICs in the player, using Vlithium_battery as the source. If we download the MAX1811 datasheet, it gives an example of a battery charger. http://datasheets.maxim-ic.com/en/ds/MAX1811.pdf Input Supply Current (from USB) Shutdown, EN = GND 6 µA BATT Leakage Current (Input Power Removed) VBATT = 4.2V, IN = GND 10 µA The 10 µA number is the one we'd be worried about. If the battery pack was 100maH, then divide 100 / 0.01 to get the hours before the battery pack is drained by the charger chip. That is a bit more than a year. The losses of the battery itself, could be worse than that. That second figure, takes into account an operating condition where "IN = GND", which might be apparent if you leave the MP3 plugged into the computer, then kill the power via the switch on the back of the computer. That would give approximately "IN = GND". If you unplug the player, the leakage could be a number less than 10uA. To keep that level of current in perspective, that is about 5 times what a digital watch draws, or about the same amount of current as the RTC in your computer draws, to run the digital clock that keeps time when the PC is powered off. There can be all sorts of failure modes, related to portions of the player drawing current, after it has been "turned off". That is as likely a failure mode, as the charger chip providing a reverse path to drain the battery. And the batteries aren't exactly champs either, as lithium gets old fast. A good reason for the battery to be user replaceable (if someone at Apple was listening). Paul |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
MP3 player is not recognised (+ other USB devices) | seht | Packard Bell Computers | 4 | September 25th 07 03:47 AM |
USB MP3 player - control from the PC? | Noozer | General | 1 | July 2nd 06 09:52 AM |
usb mp3 player pen drive | [email protected] | General | 2 | September 27th 05 10:13 AM |
Hack USB MP3 players to run from USB power instead of battery when connected to PC? | Noozer | General | 1 | August 13th 05 02:56 AM |
Please help USB MP3+ | sooeze | Creative Sound Blaster Cards | 0 | September 30th 04 06:57 PM |