USB3370 datasheet(29/75 Pages) MICROCHIP

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DS00001915B-page 29

USB3370

5.7.5

EXTERNAL VBUS INDICATOR

The USB3370 has fully implemented the External VBUS detection described in the ULPI 1.1 specification. The block

diagram of the External VBUS detection is shown in Figure 5-8 and in Table 5-4.

Note 5-5

Microchip does not recommend using the ExternalVbus signal qualified with the internal VbusVld

comparator.

Note 5-6

A peripheral should not use VbusVld to begin operation. The peripheral should use SessVld because

the internal VbusVld threshold can be above the Vbus voltage required for USB peripheral operation.

A host PHY may use an active high or low fault by setting the IndicatorComplement bit [5] in the Interface Control reg-

ister. Also this implementation supports the IndicatorPassThru bit [6] in the Interface Control register, which allows a

choice of having the External Vbus input qualified (and’ed) with the external vbus comparator output. To use the External

Vbus Input the UseExternalVbusIndicator bit [7] must be set in the OTG control register. The default is not to use this

input.

The EXTVBUS pin has a built in pull down resistor that is controlled by the UseExternalVbusIndicator bit [7] of the OTG

control register. When UseExternalVbusIndicator is set to 0 (default) the pull down resistor is activated to prevent the

pin from floating when it is unused. When UseExternalVbusIndicator is set to 1 the pull down resistor is disconnected.

FIGURE 5-9:

USB3370 DRIVES CONTROL SIGNAL (CPEN_N) TO EXTERNAL VBUS SWITCH

TABLE 5-6:

EXTERNAL VBUS INDICATOR LOGIC

Typical

Application

Use External

VBUS Indicator

Indicator Pass

Thru

Indicator

Complement

RXCMD VBUS Valid

Encoding Source

OTG Device

Internal VbusVld comparator (Default)

External active high VbusVld signal

External active low VbusVld signal

External active high power fault signal

qualified with internal VbusVld comparator.

(Note 5-5)

External active low power fault signal

qualified with internal VbusVld comparator.

(Note 5-5)

Standard Host

External active high power fault signal

External active low power fault signal

Standard

Peripheral

Internal VbusVld comparator. This should

not be used by the Link. (Note 5-6)

VBUS

Switch

OUT

USB Transceiver

VBUS

USB

Connector

VBUS

RVBUS

CPEN_N

Link

Controller

CPEN_N Logic

DrvVbusExternal

DrvVbus

ULPI

+5V

VBUS

Supply

RPU

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