Each APLL has a post divider which provides a VCO post divider frequency calculated in Equation 6 or Equation 7. The final output frequency is calculated by dividing from the VCO post divider frequency and the output divide as calculated in Equation 8. For each output, the output frequency depends on the selected APLL clock source and output divider value.
Equation 6. APLL2 selected: fPOST_DIV = fVCO2 / PnAPLL2
Equation 7. APLL1 selected: fPOST_DIV = fVCO1 / PnAPLL1
Equation 8. OUT[0:11]: fOUTx = fPOST_DIV / ODOUTx
where
- fPOST_DIV: Output mux source frequency (APLL2 or APLL1 post-divider clock)
- PnAPLL2: APLL2 primary "P1" post-divide value (2 to 13) or secondary "P2" post-divide value (2 to 3)
- PnAPLL1: APLL1 post-divide value (1 to 8)
- fOUTx: Output clock frequency (x = 0 to 15)
- ODOUTx: OUTx output bypass or divider value. All outputs have a 12-bit divider with values 1 to (212 - 1). All outputs except OUT2 and OUT3 have the option to follow the 12-bit divider with a 20-bit SYSREF divider that can be used to produce 1PPS or other frequencies below 1Hz when the SYSREF output is set for continuous output.