USB2513 datasheet(31/72 Pages) SMSC

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USB 2.0 Hi-Speed Hub Controller

Datasheet

SMSC USB251x

Revision 1.0 (3-11-09)

DATASHEET

Chapter 7 Battery Charging Support

7.1

General Description

The battery charging feature is only available in USB251xB (which represents USB2512B/3B/4B and

USB2512Bi/3Bi/4Bi hub family products). Any one or combination of downstream ports on the

USB251xB hub can be configured to support battery charging.

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

the USB Battery Charging specification, version 1.1. The hub can be configured to individually enable

each downstream port for battery charging support either via pin strapping as illustrated in Figure 7.1

or by setting the corresponding configuration bits via EEPROM or SMBus.

Figure 7.1 Battery Charging via External Power Supply

7.2

USB Battery Charging

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

7.2.1

Special Behavior of PRTPWR Pins

The SMSC hub enables VBUS by asserting the port power (PRTPWR) pin as soon as the hardware

configuration process has completed. If the port detects an over-current condition, PRTPWR will be

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

hub is not enumerated, PRTPWR can only be turned on from the host or if RESET_N is toggled. These

USB251xB/xBi

VBUS

PRTPWR[x]

FLAG

OCS_N[x]

RSTRAP

3.3 V

5 V

Note: RSTRAP enables battery charging.

USB Port Power

Controller

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