STW4810 datasheet(36/72 Pages) STMICROELECTRONICS

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4 Functional description

STw4810

36/72

Rev3

VBUS monitoring

These comparators monitor the VBUS voltage. They detect the current status of the VBUS line:

●

VBUS > 4.4 V means VBUS_VALID

●

2 V<VBUS<4.4 V means SESSION_VALID

●

VBUS<0.8 V means SESSION_END

These three bits generate an interrupt when active (see USB interrupt registers).

VUSB LDO: Internal regulator which provides power supply for the bus driver and receiver.

ID detector: This block detects the status of the ID line. It is capable of detecting three different

states of line: ball is floating ID_FLOAT high, ball is tied to ground ID_GND high and ball ID is

grounded via resistor. This detection generates interrupts (see USB interrupt registers).

Transceiver: The driver can operate in several different modes. It can act as a classical low-

speed and full-speed differential driver, as two independent single-ended drivers or as a single-

ended driver in UART mode. This block contains one differential receiver for the USB mode of

operation and two single-ended receivers for USB signaling and UART mode.

DP monitor: This block is used to detect car kit peripheral (0.6 V on DP).

Pull up and pull down resistor: Configurable integrated pull-up and pull-down resistor of data

line and VBUS.

4.4.2

Modes and operations

Power modes

The transceiver power modes are:

●

Active power mode

●

Suspended power mode

●

Power down mode

In suspended power mode the differential transmitter and receiver are turned off to save power

but the USB interface is still active (pull-up and pull-down on, VBUS on). In power down mode,

only the serial interface is active and the transceiver is able to detect SRP. In power down

mode, ID ball sensing can be turned on/off via a control bit in the control registers.

USB modes

The two transceiver modes are:

●

DAT_SEO mode (dat_se0 = 1 in USB control register 1 -

Table 10)

●

VP_VM mode (dat_se0 = 0 in USB control register 1 -

Table 10)

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