SI51218 Datasheet, PDF (8/13 Pages) Silicon Laboratories – THREE OUTPUTS FACTORY PROGRAMMABLE CLOCK GENERATOR

Si51218
3. Functional Description
3.1. Input Frequency Range
The input frequency range is from 8.0 to 48.0 MHz for crystals and ceramic resonators. If an external clock is used,
the input frequency range is from 8.0 to 166.0 MHz.
3.2. Output Frequency Range and Outputs
Up to three outputs can be programmed as CLKOUT or REFOUT. CLKOUT output can be synthesized to
frequency value from 32.768 kHz to 200 MHz. REFOUT is the buffered output of the oscillator and is the same
frequency as the input frequency. REFOUT2 (pin6) frequency can also be programmed to input frequency divided
by 2 to 32. By using only low cost, fundamental mode crystals, the Si51218 can synthesize output frequency up to
200 MHz, eliminating the need for higher order crystals (Xtals) and crystal oscillators (XOs). The 32.768 kHz output
can replace the 32.768 kHz crystal which is widely used in many embedded and mobile systems. This reduces the
cost while improving the system clock accuracy, performance, and reliability.
3.3. Frequency Select (FSEL)
The Si51218 pin 4 and 6 can be programmed as frequency select input (FSEL). If FSEL function is used, one
output pin can switch between two predefined frequencies by FSEL input. The set of frequencies in Table 5 is given
as an example.
Table 5. Example Frequencies
FSEL
(Pin 6)
0
CLKOUT3
(Pin 7)
66 MHz
1
33 MHz
3.4. Power Down (PD) or Output Enable (OE)
The Si51218 pin 6 can be programmed as PD input. Pin 4 and pin 6 can be programmed as OE input. PD turns off
both PLL and output buffers whereas OE only disables the output buffers to Hi-Z.
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Rev. 1.0