Although not sanctioned by the USB 2.0 Specification, charging batteries from VBUS
of USB is not prohibited. Thus, devices that charge their batteries from USB may be certified provided they pass average current and transient current tests as defined below. These tests are in addition to the compliance tests required for all devices.
- All battery powered devices must test with a dead battery. A dead battery is defined by a device that is unable to successfully power on when not attached to an external power supply (such as USB or an AC adapter).
- Once the device has asserted its pull-up, it must fully comply with the USB 2.0 Specification.
- When unconfigured, the upstream port must never consume more than ICCINIT (100mA)
- When configured, the upstream port must never consume more current than its active bMaxPower value. If current draw exceeds 100mA, the device must report itself as bus-powered during enumeration.
- If a peripheral is unable to connect (assert its pull-up) due to a dead battery, it must never consume more than ICCINIT (100mA) including when attached to a suspended downstream port.
- If a peripheral is able to connect (assert its pull-up) with a dead battery, it must fully abide by the USB 2.0 Specification and the USB-IF Compliance Program in regards to power draw.
- The peripheral must pass Inrush tests with a dead battery.
- If the peripheral is not able to charge its batteries from USB with a dead battery, then the battery is permitted to be charged to the point where it is able to power on using its battery. The peripheral is permitted to be tested from a low battery state, but with the peripheral turned off.
- If the peripheral is not able to charge its batteries from USB with a low battery while in an off state, then the peripheral is permitted to be tested with a low battery while turned on.
- A device that uses USB to charge its batteries must enumerate correctly on the host system.
The average current draw of a device while in the Powered Device State (Section 9.1.1 of the USB 2.0 Specificiation) is to be measured on all upstream ports. The test is performed using the USB20CV utility along with unconfigured and configured current measurements.
- Conduct the unconfigured and configured current measurements as usual
- After taking the configured current measurement, do not end the test in USB20CV
- Detach the average current text fixture from the downstream port
- After a couple of seconds, re-attach the average current test fixture to the same downstream port
- Wait one second. Measure the current.
Scoring: USB peripherals must draw no more that 2.5mA; however, battery-powered peripherals may consume 100mA or less.