USB 2.0 Hi-Speed Hub Controller

Datasheet

Chapter 10 AC Specifications

10.1Oscillator/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.

XTAL1

(CS1 = CB + CXTAL )

C1

 

Crystal

CL

1 Meg

 

 

 

 

 

C2

XTAL2

(CS2 = CB + CXTAL )

Figure 10.1 Typical Crystal Circuit

Note: CB equals total board/trace capacitance.

(C1 + CS1) x (C2 + CS2)

CL =

(C1 + CS1 + C2 + CS2)

Figure 10.2 Formula to Find the Value of C1 and C2
C = (2 x CL) - Cs
Figure 10.3 Simplified Form of the Capacitance Formula
10.1.1SMBus 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).

10.1.2I2C EEPROM:

Clock frequency is fixed at 60 KHz ± 20%.

10.1.3USB 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.

Revision 1.0 (3-11-09)

66

SMSC USB251x

DATASHEET