STW4810BHD datasheet(41/72 Pages) STMICROELECTRONICS

41 / 72 page

STw4810

4 Functional description

Rev3

41/72

ID detector

In either active or suspended power mode, the ID detector detects the condition of the ID line

and differentiates between the following three conditions:

–

ID ball floating: (e.g. with USB B-device connected)

–

ID ball shorted to ground: (e.g. with USB A-device connected)

–

ID ball connected to ground through resistor RACC_ID: (e.g.with an accessory).

The transceiver pulls the ID ball to VID_HI (VBAT) through a resistance of RID_PU when an

accessory is plugged in. In this case, the ID ball is externally connected to ground via Racc_ID

resistor.

Two comparators are used to detect the ID voltage: VID_GND and VID_FLOAT.

The ID detector also has a switch that can be used to ground the ID ball. This switch is

controlled by id_gnd bit of USB control register 2 (

Table 11); This pull-down is used for

CEA_KARKIT purposes.

Car kit interrupt detector

The transceiver is able to detect when the DP line is below the Carkit Interrupt threshold ‘cr_int’,

(see USB interrupt register) (refer to OTG specifications, Rev 0.92, §2.7, p13).

Charge pump

From VBAT_USB, the charge pump supplies VBUS, ‘vbus_drv’ bit of USB control register 2

(

Table 11) is used to enable/disable the charge pump.

LDO USB

From VBAT_USB, a LDO provides VUSB supply, ‘usb_en’ bit of USB_EN register (

Table 16) is

used to enable/disable the VUSB LDO.

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