USB3813 datasheet(37/57 Pages) MICROCHIP

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USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications

Datasheet

 2014 Microchip Technology Inc.

DS00001715A-page 37

If a custom charger detection algorithm is desired, the SMBus registers can also be used to control

the charger detection block to implement a custom charger detection algorithm. In order to avoid

negative interactions with automatic battery charger detection or normal hub operation, the user should

only attempt Custom battery charger detection during the Hub.Config stage or Hub.Connect stage. No

logic is implemented to disable custom detection at other times - it is up to the user software to observe

this restriction.

The SMBus registers and associated general purpose interrupts are primarily intended for

communication with the SOC. To facilitate operation when the SOC is not in a mode which can service

the SMBus, additional output signals dedicated specifically to charger detection (CHRGDET[1:0]) are

provided. This output can be used to communicate with a second device such as a PMIC. The type

of charger which affects the CHRGDET[1:0] state can be selected in the Charge Detect Mask Register.

There is a possibility that the system is not running the reference clock when battery charger detection

is required (for example if the battery is dead or missing). During the Hub.WaitRefClk stage the battery

charger detection sequence can be configured to be followed regardless of the activity of REFCLK by

relying on the operation of the internal oscillator.

Note: Battery charger detection is not available when utilizing HSIC on the upstream port.

8.1.1.1

Charger Detection (CHRGDET[1:0])

The CHRGDET[1:0] output function can be programmed to communicate information that can affect

the level of current that the system may draw from the upstream USB VBUS wire. CHRGDET[1:0] can

be set to identify that a specific type of charger was discovered or that an event on the device occurred

such as USB Device Suspend or the USB Device has been configured. Either bit of the function can

be enabled on a single pin if the resolution of two pins is not required. The output function tracks the

CHG_DET[1:0] bits of the .

The charger detect output can be used to communicate directly to a PMIC GPIO that a charger has

been identified. In this way, there is no communication required over the SMBus by the SOC. This

facilitates a dead battery case where there is insufficient battery power to activate the SOC or its

SMBus to query the cause of an interrupt. The encoding of CHRGDET[1:0] can be seen in Table 8.2.

Apple Charger Low Current Charger (500mA)

DP=2.0V

DM=2.0V

100

Apple Charger High Current Charger (1000mA)

DP=2.0V

DM=2.7V

101

Table 8.2 CHRGDET[1:0] Configuration Definitions

CHRGDET[1:0]

DEFINITION

‘00’

No selected chargers or status identified.

Draw no current from VBUS.

‘01’

VBUS detect without enumeration.

Draw unconfigured current from VBUS (100mA max).

‘10’

Device enumerated, Set Config seen.

Draw configured current from VBUS (500mA max).

Table 8.1 Chargers Compatible with Upstream Detection (continued)

USB ATTACH TYPE

DP/DM PROFILE

CHARGERTYPE

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