USB2512 datasheet(66/72 Pages) SMSC

66 / 72 page

USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 1.0 (3-11-09)

SMSC USB251x

DATASHEET

Chapter 10 AC Specifications

10.1

Oscillator/Clock

Crystal: Parallel Resonant, Fundamental Mode, 24/481 MHz

±350 ppm.

External Clock: 50% Duty cycle

± 10%, 24/48 MHz ± 350 ppm, Jitter < 100 ps rms.

Figure 10.1 Typical Crystal Circuit

Note: CB equals total board/trace capacitance.

Figure 10.2 Formula to Find the Value of C1 and C2

Figure 10.3 Simplified Form of the Capacitance Formula

10.1.1

SMBus Interface:

The SMSC Hub conforms to all voltage, power, and timing characteristics and specifications as set

forth in the SMBus 1.0 specification for Slave-Only devices (except as noted in Section 8.3).

10.1.2

I2C EEPROM:

Clock frequency is fixed at 60 KHz

± 20%.

10.1.3

USB 2.0

The SMSC Hub conforms to all voltage, power, and timing characteristics and specifications as set

forth in the USB 2.0 specification. Please refer to the USB 2.0 specification for more information.

1.Only when SEL48 is available and supported.

XTAL1

(CS1 = CB + CXTAL )

XTAL2

(CS2 = CB + CXTAL )

1 Meg

Crystal

(C1 + CS1) x (C2 + CS2)

(C1 + CS1 + C2 + CS2)

CL =

C = (2 x CL) - Cs

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