USB3300 datasheet(39/53 Pages) MICROCHIP

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DS00001783B-page 39

USB3300

7.0

APPLICATION NOTES

The USB3300 requires few external components as shown in the application diagrams. In some applications, the power

supplied on the VBUS and GND pins of the USB connector is used as the source of system power. The USB2.0 standard

restricts the voltage at the VBUS pin to a maximum value of 5.25V. In some applications, it may be required to provide

protection to the USB3300 VBUS pin if the VBUS voltage exceeds the USB2.0 specifications.

One method of protecting the VBUS pin from excessive voltage (transients) is to place a resistor (RVBUS) in series as

shown in Figure 7-1, "USB3300 Application Diagram (Peripheral)" and Figure 7-2, "USB3300 Application Diagram

(Host or OTG)". The resistor provides protection against transients that exceed the value of VVBUS provided in Table 4-

2, "Recommended Operating Conditions". When RVBUS is installed, the transient must not be allowed to exceed the

value of VVBUS for longer than 500 μs.

To protect the VBUS pin against a steady state voltage on the USB connector that exceeds the value of VVBUS provided

in Table 4-2, an Over Voltage Protection (OVP) component can be used as shown in Figure 7-3, "USB3300 Application

Diagram (Peripheral with Over Voltage Protection)".

In addition to the capacitors shown in the application diagrams, each VDD pin should have an additional capacitor to

ground, of value 0.01 or 0.1

μF (not shown for clarity). Approximately equal numbers of each value should be used.

TABLE 7-1:

COMPONENT VALUES IN APPLICATION DIAGRAMS

Reference

Designator

Value

Description

Notes

COUT

4.7

μF

Bypass capacitors to ground (<1

Ω ESR)

for regulator stability.

Place as close as possible to the

PHY.

CVBUS

See Table 7-2,

"Capacitance

Values at VBUS of

USB Connector"

Capacitor to ground required by the

USB Specification. Microchip

recommends <1

Ω ESR.

Place near the USB connector.

CBYP

System dependent. Bypass capacitor to ground.

Place as close as possible to the

PHY.

CDC_BLOCK

System dependent. The USB connector housing may be

AC-coupled to the device ground.

Industry convention is to ground

only the host side of the cable

shield.

RVBUS

Max of 820

Ω in

Host or OTG

applications.

Series resistor to reduce any transient

voltage on the VBUS pin of the

USB3300.

The transient must not be allowed

to exceed the value of VVBUS for

longer than 500

μs

Okay to leave No Connection (NC)

in device mode.

TABLE 7-2:

CAPACITANCE VALUES AT VBUS OF USB CONNECTOR

MODE

MIN Value

MAX Value

Host

120

μF

Device

μF10μF

OTG

μF6.5μF

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