STW4811M STMicroelectronics, STW4811M Datasheet - Page 52

• Manufacturer Part Number: STW4811M
• Description: Power Management For Multimedia Processors
• Manufacturer: STMicroelectronics

Functional description
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If the B-device is in correct condition to start a new session, it first performs data line
pulsing, followed by VBUS pulsing. When VBUS next crosses the SESSION VALID
threshold, the B- device considers a session to be in progress and asserts the DP or DN
data line within 100 ms. After SRP initialization, the B- device is set up to wait for at least 5
seconds for the A-device to respond before informing the user that the consumption attempt
has failed.
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At the start of a session, the A-device has the role of host as default. During a session, the
host role can be transferred back and forth between the A-device and the B-device any
number of times using the Host Negotiation Protocol (HNP). The sequence of events for this
exchange of host role is described in the “On the Go Supplement to the USB 2.0
Specification” (rev 1.0) as follow:
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:
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●
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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 (
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 (
p13).
Charge pump
From VBAT_USB, the charge pump supplies VBUS, ‘vbus_drv’ bit of USB control register 2
(
If VBUS is “ON” before going to sleep mode, it remains “ON” in sleep mode.
LDO USB
From VBAT_USB, a LDO provides VUSB supply, ‘usb_en’ bit of USB_EN register (
is used to enable/disable the VUSB LDO and the transceiver.
Table 12
Session Request Protocol (SRP)
Host Negotiation Protocol (HNP)
–
–
–
–
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).
) is used to enable/disable the charge pump.
The A-device puts the bus in the suspend state
The B-device simulates a disconnect by de-asserting its DP pull-up
The A-device detects SE0 on the bus and asserts its DP pull-up
The B-device detects that DP line is high and takes the role of the host.
Table 13
)) (refer to OTG specifications, Rev 0.92, §2.7,
Table 12
); This pull-down is used for
STw4811M/STw4811N
Figure 13
Table 17
).
)