USB334X datasheet(77/92 Pages) MICROCHIP

77 / 92 page

 2009-2018 Microchip Technology Inc.

DS00002646A-page 77

USB334x

8.0

APPLICATION NOTES

8.1

Application Diagram

The USB334x requires few external components as shown in the application diagrams. The USB 2.0 Specification

restricts the voltage at the VBUS pin to a maximum value of 5.25V. In some applications, the voltage will exceed this

limit, so the USB334x provides an integrated over voltage protection circuit. The over voltage protection circuit works

with an external resistor (RVBUS) to lower the voltage at the VBUS pin.

TABLE 8-1:

COMPONENT VALUES IN APPLICATION DIAGRAMS

REFERENCE

DESIGNATOR

VALUE

DESCRIPTION

NOTES

COUT

See Table 4-12

Bypass capacitor to ground (<1Ω ESR)

for regulator stability.

Place as close as possible to the

PHY.

CVBUS

See Table 8-2

Capacitor to ground required by the USB

Specification. Microchip recommends

<1Ω ESR.

Place near the USB connector.

CBYP

System

dependent.

Bypass capacitor to ground. Typical

values used are 0.1 or 0.01 µF.

Place as close as possible to the

PHY.

CDC_LOAD

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

 or 20k

Series resistor to work with internal over

voltage protection.

See Section 5.7.2.6, "VBUS Over

Voltage Protection (OVP)," on

page 37 for information regarding

power dissipation.

RBIAS

8.06k

 (±1%)

Series resistor to establish reference

voltage.

See Section 5.3, "Bias

Generator," on page 27 for

information regarding power

dissipation.

TABLE 8-2:

CAPACITANCE VALUES AT VBUS OF USB CONNECTOR

MODE

MIN VALUE

MAX VALUE

Host

120µF

Device

1µF

10µF

OTG

1µF

6.5µF

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