USB20H04 datasheet(14/38 Pages) SMSC

14 / 38 page

4-Port USB2.0 Hub Controller

Datasheet

Revision 1.63 (10-14-04)

Page 14

SMSC USB20H04

DATASHEET

Table 4.4 - Biasing and Clock Oscillator Signals

NAME

BUFFER

TYPE

ACTIVE

LEVEL

DESCRIPTION

RBIAS

I-R

N/A

External 1% bias resistor. Requires a 12K

Ω resistor to ground. Used for

setting HS transmit current level and on-chip termination impedance.

XTAL1/CLKIN

ICLKx

N/A

External crystal. 24MHz crystal or external clock input when a crystal is not

used.

Connect a 5M ohm resistor from this pin to XTAL2 when a crystal is used.

XTAL2

OCLKx

N/A

External crystal. 24MHz crystal. Not connected when using an external clock.

CLKIN_EN

High

Clock Input Enable. When high, an external CMOS clock drives XTAL1.

Table 4.5 - Power and Ground Signals

NAME

BUFFER

TYPE

ACTIVE

LEVEL

DESCRIPTION

VDD3.3

N/A

3.3V Digital Supply. Powers digital pads.

VDD1.8

N/A

1.8V Digital Supply. Powers digital core.

VSS

N/A

Signal Ground.

VDDA3.3

N/A

3.3V Analog Supply. Powers analog I/O and 3.3V analog circuitry.

VDDA1.8

N/A

1.8V Analog Supply. Powers 1.8V analog circuitry.

4.2

Buffer Type Descriptions

Table 4.6 – USB20H04 Buffer Type Descriptions

BUFFER

DESCRIPTION

Input

IPU

Input with weak internal pull-up resistor.

IPD

Input with weak internal pull-down resistor

Input with Schmitt trigger

IO8

Input/Output with 8mA drive

IOSD12

Open drain with 12mA sink with Schmitt

trigger. Meets I2C-Bus Spec Version 2.1

Output with 8mA drive

OD8

Open drain with 8mA sink

ICLKx

XTAL clock input

OCLKx

XTAL clock output

IO-U

Defined in USB specification

Analog Output

I-R

3.3V Tolerant Analog Pin

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