USB333X datasheet(36/85 Pages) MICROCHIP

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USB333x

DS00001880A-page 36

 2009 - 2015 Microchip Technology Inc.

The Over voltage Protection circuit is designed to protect the USB333x from continuous voltages up to 30V on the

RVBUS resistor.

The RVBUS resistor must be sized to handle the power dissipated across the resistor. The resistor power can be found

using the equation below:

For example, protecting a peripheral or device only application to 15V would require a 20kΩ RVBUS resistor with a power

rating of 0.01W. To protect an OTG product to 15V would require a 1kΩ RVBUS resistor with a power rating of 0.1W.

5.6.3

DRIVING EXTERNAL VBUS

The USB333x monitors VBUS as described in VBUS Monitoring and VBUS Pulsing. The USB333x does not provide an

external output for the DrvVbusExternal ULPI register. For OTG and Host applications, the external VBUS supply or

power switch must be controlled by the Link as shown in Figure 8-2.

5.7

USB UART Support

The USB333x provides support for the USB UART interface as detailed in the ULPI specification and the former CEA-

936A specification. The USB333x can be placed in UART Mode using the method described in Section 6.7, and the

regulator output will automatically switch to the value configured by the UART RegOutput bits in the USB IO & Power

Management register. While in UART mode, the Linestate signals cannot be monitored on the DATA[0] and DATA[1]

pins.

5.8

USB Charger Detection Support

The following blocks allow the USB333x to detect when a Battery Charger, Charging Host Port, or a USB Host is

attached to the USB connector. The USB333x can also be configured to appear as a Charging Host Port. The charger

detection circuitry should be disabled during USB operation.

TABLE 5-8:

REQUIRED RVBUS RESISTOR VALUE

Operating Mode

RVBUS

Device only

20kΩ ±5%

OTG Host Capable of less than 100mA of

current on VBUS

1kΩ ±5%

Host or OTG Host capable of >100mA

UseExternalVbusIndicator = 1

1kΩ ±5%

RVBUS

Vprotect

5.0

–

()

VBUS

--------------------------------------------

Where:

• Vprotect is the VBUS protection required.

•RVBUS is the resistor value, 1kΩ or 20kΩ.

•PRVBUS is the required power rating of RVBUS.

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