USB2533 datasheet(58/61 Pages) SMSC

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USB 2.0 Hi-Speed 3-Port Hub Controller

Datasheet

Revision 1.0 (06-17-13)

SMSC USB2533

DATASHEET

9.6

Clock Specifications

The device can accept either a 24 MHz crystal or a 24 MHz single-ended clock oscillator input. If the

single-ended clock oscillator method is implemented, XTAL1 should be left unconnected and REFCLK

should be driven with a clock that adheres to the specifications outlined in Section 9.6.2, "External

Reference Clock (REFCLK)".

9.6.1

Oscillator/Crystal

It is recommended that a crystal utilizing matching parallel load capacitors be used for the crystal

input/output signals (XTAL1I/XTAL2). See Table 9.6 for the recommended crystal specifications.

Note 9.6

0oC for commercial version, -40oC for industrial version.

Note 9.7

+70oC for commercial version, +85oC for industrial version.

9.6.2

External Reference Clock (REFCLK)

The following input clock specifications are suggested:



50% duty cycle

± 10%



24 MHz

± 350 PPM

Note: The external clock is recommended to conform to the signalling levels designated in the

JEDEC specification on 1.2V CMOS Logic. XTAL2 should be treated as a no connect when an

external clock is supplied.

Table 9.6 Crystal Specifications

PARAMETER

SYMBOL

MIN

NOM

MAX

UNITS

NOTES

Crystal Cut

AT, typ

Crystal Oscillation Mode

Fundamental Mode

Crystal Calibration Mode

Parallel Resonant Mode

Frequency

Ffund

24.000

MHz

Total Allowable PPM Budget

+/-350

PPM

Operating Temperature Range

Note 9.6

Note 9.7

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