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:

A

Output Frequency = Input Frequency

×

B

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.

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.

AV9108

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