USB333X datasheet(33/85 Pages) MICROCHIP

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DS00001880A-page 33

USB333x

The ID resistance to ground can be read while the USB333x is in Synchronous Mode. When a resistor to ground is

attached to the ID pin, the state of the IdGnd comparator will change. After the Link has detected ID transition to ground,

it can use the methods described in Section 6.8 to operate the Rid converter.

5.6.1.3

Using IdFloat Comparator (not recommended)

The ID pin can be either grounded, floated, or connected to ground with a 102kΩ external resistor. To detect the 102K

resistor, set the idPullup bit in the OTG Control register, causing the USB333x to apply the 100K internal pull-up con-

nected between the ID pin and VDD33. Set the idFloatRise and idFloatFall bits in the Carkit Interrupt Enable register to

enable the IdFloat comparator to generate an RXCMD to the Link when the state of the IdFloat changes. As described

in Figure 6-3, the alt_int bit of the RXCMD will be set. The values of IdGnd and IdFloat are shown for the three types

cables that can attach to the USB Connector in Table 5-6.

To save current when an A Plug is inserted, the internal 102kΩ pull-up resistor can be disabled by clearing the IdPullUp

bit in the OTG Control register and the IdFloatRise and IdFloatFall bits in both the USB Interrupt Enable Rising and USB

Interrupt Enable Falling registers. If the cable is removed the weak RIDW will pull the ID pin high.

The IdGnd value can be read using the ULPI USB Interrupt Status register, bit 4. In host mode, it can be set to generate

an interrupt when IdGnd changes by setting the appropriate bits in the USB Interrupt Enable Rising and USB Interrupt

Enable Falling registers. The IdFloat value can be read by reading the ULPI Carkit Interrupt Status register bit 0.

5.6.2

VBUS MONITORING AND VBUS PULSING

The USB333x includes all of the VBUS comparators required for OTG. The VbusValid, SessVld, and SessEnd compar-

ators shown in Figure 5-10 are fully integrated into the USB333x. These comparators are used to monitor changes in

the VBUS voltage, and the state of each comparator can be read from the USB Interrupt Status register.

The VbusValid comparator is used by the Link, when configured as an A device, to ensure that the VBUS voltage on

the cable is valid. The SessVld comparator is used by the Link when configured as both an A or B device to indicate a

session is requested or valid. Finally the SessEnd comparator is used by the B-device to indicate a USB session has

ended.

Also included in the VBUS Monitor and Pulsing block are the resistors used for VBUS pulsing in SRP. The resistors used

for VBUS pulsing include a pull-down to ground and a pull-up to VDD33.

In some applications, voltages much greater than 5.5V may be present at the VBUS pin of the USB connector. The

USB333x includes an over voltage protection circuit that protects the VBUS pin of the USB333x from excessive voltages

as shown in Figure 5-10.

Note:

The ULPI specification details a method to detect a 102kΩ resistance to ground using the IdFloat compar-

ator. This method can only detect 0ohms, 102kΩ, and floating terminations of the ID pin. Due to this limita-

tion it is recommended to use the RID Converter as described in Section 5.6.1.2.

TABLE 5-6:

IDGND AND IDFLOAT VS. ID RESISTANCE TO GROUND

ID Resistance

IDGND

IDFLOAT

Float

102K

GND

Note:

The ULPI register bits IdPullUp, IdFloatRise, and IdFloatFall should be enabled.

Note:

The IdGnd switch has been provided to ground the ID pin for future applications.

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