AV9108
Frequency Accuracy and Calculation
The accuracy of the frequencies produced by the
ICS9108
depends on the input frequency and the desired actual output
frequency. The formula for calculating the exact frequency is
as follows:
Output Frequency = Input Frequency
×
where A=2, 3, 4 ... 128, and
B=2, 3, 4 ... 32.
For example, to calculate the actual output frequency for a
video monitor expecting a 44.900 MHz clock and using a
14.318 MHz input clock, the closest A/B ratio is 69/22, which
gives an output of 44.906 MHz (within 0.02% of the target
frequency). Generally, the
ICS9108
can produce frequencies
within 0.1% of the desired output.
A
B
Allowable Input and Output Frequencies
The input frequency should be between 2 and 32 MHz and the
A/B ratio should not exceed 24. The output should fall in the
range of 2-120 MHz.
Output Enable
The Output Enable feature tristates the specified output clock
pins. This places the selected output pins in a high impedance
state to allow for system level diagnostic testing.
Power-Down
If equipped, the power-down shuts off the specified PLL or
entire chip to save current. A few milliseconds are required to
reach full functioning speed from a power-down state.
Frequency Transitions
A key
ICS9108
feature is the ability to provide glitch-free frequency transitions across its output frequency range. The
ICS9108
provides smooth transitions between any of the two groups of eight frequencies (when FS3=0 or FS3=1), so that the device will
switch glitch-free between 4-100 MHz and 2-50 MHz.
4
ICS [ INTEGRATED CIRCUIT SYSTEMS ]
