USB 2.0 Hi-Speed 2-Port Hub Controller
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.
Table 9.6 Crystal Specifications
PARAMETER
SYMBOL
MIN
NOM
MAX
UNITS
NOTES
Crystal Cut
AT, typ
Fundamental Mode
Parallel Resonant Mode
Crystal Oscillation Mode
Crystal Calibration Mode
Frequency
Ffund
-
24.000
-
MHz
PPM
oC
Total Allowable PPM Budget
Operating Temperature Range
-
-
-
+/-350
Note 9.7
Note 9.6
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.
SMSC USB2532
57
Revision 1.0 (06-17-13)
DATASHEET
SMSC [ SMSC CORPORATION ]
