USB333X datasheet(34/85 Pages) MICROCHIP

34 / 85 page

USB333x

DS00001880A-page 34

 2009 - 2015 Microchip Technology Inc.

5.6.2.1

SessEnd Comparator

The SessEnd comparator is used during the Session Request Protocol (SRP). The comparator is used by the B-device

to detect when a USB session has ended and it is safe to start Vbus Pulsing to request a USB session from the A-device.

When VBUS goes below the threshold in Table 4-8, the USB session is considered to be ended, and SessEnd will tran-

sition from 0 to 1. The SessEnd comparator can be disabled by clearing this bit in both the USB Interrupt Enable Rising

and USB Interrupt Enable Falling registers. When disabled, the SessEnd bit in the USB Interrupt Status register will read

The SessEnd Comparator is only used when configured as an OTG device. If the USB333x is used as a Host or Device

only the SessEnd Comparator should be disabled, using the method described above.

5.6.2.2

SessVld Comparator

The SessVld comparator is used when the PHY is configured as both an A and B device. When configured as an A

device, the SessVld is used to detect Session Request protocol (SRP). When configured as a B device, SessVld is used

to detect the presence of VBUS. The SessVld comparator output can also be read from the USB Interrupt Status regis-

ter. The SessVld comparator will also generate an RX CMD, as detailed in Section 6.3.1, anytime the comparator

changes state. The SessVld interrupts can be disabled by clearing this bit in both the USB Interrupt Enable Rising and

USB Interrupt Enable Falling registers. When the interrupts are disabled, the SessVld comparator is still operational and

will generate RX CMD’s. The SessVld comparator trip point is detailed in Table 4-9.

FIGURE 5-10:

USB333X OTG VBUS BLOCK

Note:

The OTG Supplement specifies a voltage range for A-Device Session Valid and B-Device Session Valid

comparator. The USB333x PHY combines the two comparators into one and uses the narrower threshold

range.

VbusValid

SessValid

SessEnd

DischrgVbus

0.5V

1.4V

4.575V

VBUS

VDD33

PHY

To USB Con.

SessEnd Rise or

SessEnd Fall

VbusValid Rise or

VbusValid Fall

RXCMD VbusValid

IndicatorComplement

[UseExternalVbusindicator, IndicatorPassThru]

[0, X]

[1, 0]

[1, 1]

EXTVBUS (logic 1)

ChrgVbus

VBUS

Overvoltage

Protection

RVBUS

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