Maximum current in unconfigured state

[Chosee]

Hi!
I am designing a USB charger which has basic charger detection(primary detection), but there is no communication implemented(so it cannot enumerate). I know I can draw up to 1.5A when in a DCP/CDP, and only 100mA from an SDP. My device does pass the inrush test, but after the inrush event a peak above the 100mA for a short duration(some milliseconds) appears. Does this violate the 100mA max current from an SDP, or is the maximum current an average over time?

I read here: http://compliance.usb.org/index.asp?UpdateFile=Battery%20Charging&Format=Standard#1
"A device that uses USB to charge its batteries must enumerate correctly on the host system.".
Does this mean that I am breaking the standard since I cannot enumerate?

Thanks in advance!

[Jan Axelson]

Battery Charging Specification, Revision 1.2 says:

1.4.13 Standard Downstream Port
In this specification, a Standard Downstream Port (SDP) refers to a downstream port on a device that
complies with the USB 2.0 definition of a host or hub. An SDP expects a downstream device with a good
battery to draw less than 2.5 mA average when unconnected or suspended, up to 100 mA maximum when
connected and not configured and not suspended, and up to 500 mA maximum if so configured and not
suspended.

There is no mention of averaging over time.

Yes, it appears to say that if your charger uses a USB connection to a host system to charge its batteries and if you want the device to be certified by USB-IF, the charger should enumerate when attached to the host system. I don't know how many portable batteries comply with this requirement.

If you don't attempt certification, drawing >100mA briefly might not be an issue either though some SDPs are required to provide only 100mA.

[bpaddock]

Hi!
I am designing a USB charger which has basic charger detection(primary detection), but there is no communication implemented(so it cannot enumerate).
...

Don't know if it helps for sure without knowing more about your set up.
Take a look at the bq24392 USB charge impedance sensor  to
control how much current USB draws when plugged in to a charger vs PC,
to be compliant with USB BC 1.2 standard.

Maxim makes a similar part.

A compliant WalWart power source will have its data lines shorted to indicate it is a charger source and not a PC.
Sadly many don't, they are just open lines.