USB power requirements

[Matt-]

Hi!

I have a project, being powered off ~25v DC, with two regulated rails -- a 12v and a 5v.  I'd like to have a single USB port for charging devices, but am confused by the way in which USB devices negotiate power delivery and battery charging.  It's my understanding that higher levels of USB negotiate voltage and power delivery, but I'm unclear on basic power supply.

Can I hook the 5v power rail to a USB breakout board, and let the remote device manage battery charging and power consumption at 5v, or do I need something 'smarter' to regulate the negotiation and power delivery to the device?

Many thanks in advance.

[sleemanj]

For plain old 5v USB, yes connect 5v directly to the USB socket, and short the data pins togethor will work for most things (Android). 

If iPhone then you might need to use combination of resistors on the data pins to convince it to draw more than 500mA, google it for details.

[Matt-]

Awesome.  Thanks very much!