W681308
XXXX PRODUCT DESCRIPTION
9.
9.1
Clock Control and Reset
Clock Control
9.1.1
Overview
Each register in the 12/24/48 MHz USB Audio Controller is reset synchronously. The Reset and Clock Control function
ensures that the system reset signal is correctly generated. The system reset signal is also used to ensure that bi-directional
signals are all set to input during initialization.
9.1.2
Clock Generation
The crystal oscillator circuit and the external attachment of a 12 MHz quartz crystal or ceramic resonator is shown below.
The Rf is used to DC bias the internal amplifier to operate in the linear region. The R1, C1, and C2 are chosen so as not to
overdrive the crystal and to suppress oscillation at higher harmonics. Rf = 1MΩ, R1=270Ω, C1 and C2 are to be 33pf each.
XTAL_IN
XTAL_OUT
R1
Rf
External
Crystal
C2
C1
The PLL block diagram is shown below. The PLL uses the output of the crystal oscillator as its reference clock and generate
a 48 MHz clock.
29
Rev1.2
NUVOTEM TALEMA [ NUVOTEM TALEMA ]
