USB2422SLASHMJ datasheet(18/51 Pages) SMSC

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2-Port USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 1.0 (06-04-13)

SMSC USB2422

DATASHEET

Chapter 3 Battery Charging Support

The USB2422 SMSC hub provides support for battery charging devices on a per port basis in

compliance with the USB Battery Charging Specification, Revision 1.1. The hub can be configured to

individually enable each downstream port for battery charging support either via pin strapping (Port 1

only) as illustrated in Figure 3.1 or by setting the corresponding configuration bits via SMBus (Section

4.1 on page 20).

Figure 3.1 Battery Charging via External Power Supply

Note: RSTRAP enables battery charging.

3.1

USB Battery Charging

A downstream port enabled for battery charging turns on port power as soon as the power on reset

and hardware configuration process has completed. The hub does not need to be enumerated nor

does VBUS_DET need to be asserted for the port power to be enabled. These conditions allow battery

charging in S3, S4, and S5 system power states as well as in the fully operational state. The USB

Battery Charging Specification does not interfere with standard USB operation, which allows a device

to perform battery charging at any time.

A port that supports battery charging must be able to support 1.5 amps of current on VBUS. Standard

USB port power controllers typically only allow for 0.8 amps of current before detecting an over-current

condition. Therefore, the 5 volt power supply, port power controller, or over-current protection devices

must be chosen to handle the larger current demand compared to standard USB hub designs.

3.1.1

Special Behavior of PRTPWR Pins

The USB2422 enables VBUS by asserting the port power (PRTPWR[2:1]) as soon as the hardware

configuration process has completed. If the port detects an over-current condition, PRTPWR[2:1] will

be turned off to protect the circuitry from overloading. If an over-current condition is detected when the

hub is not enumerated, PRTPWR[2:1] can only be turned on from the host or if RESET_N is toggled.

These behaviors provide battery charging even when the hub is not enumerated and protect the hub

from sustained short circuit conditions. If the short circuit condition persists when the hub is plugged

into a host system the user is notified that a port has an over-current condition. Otherwise

PRTPWR[2:1] turned on by the host system and the ports operate normally.

USB2422

USB Port Power

Controller

FLAG

VBUS

5.0 V

3.3 V

RSTRAP

PRTPWR1

OCSx_N

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