9.3.9.1 PLL Frequency Relationships
The following equations provide the PLL frequency relationships required to achieve closed-loop operation according to the selected PLL mode. The TICS Pro programming software can be used to generate valid divider settings based on the desired frequency plan configuration and PLL mode. The equations are applicable to both PLL channels.
Equation 1 relates to the APLL:
Equation 1. f
VCO = f
XO × D
XO × (INT
APLL + NUM
APLL/ DEN
APLL)
where
- fVCO: VCO frequency
- fXO: XO input frequency
- DXO: APLL XO doubler (1 = disabled, 2 = enabled)
- INTAPLL: APLL N divider integer value (9 bits, 1 to 29-1)
- NUMAPLL: APLL N divider numerator value (40 bits, 0 to 240-1)
- DENAPLL: APLL N divider denominator value (fixed, 240)
Equation 2 relates to the TCXO-DPLL:
Equation 2. f
VCO = (f
TCXO × D
TCXO / M
TCXO) × P1
PLL × PR
TCXO × (INT
TCXO + NUM
TCXO/ DEN
TCXO)
where
- fTCXO: TCXO/OCXO input frequency
- DTCXO: TCXO input doubler (1 = disabled, 2 = enabled)
- MTCXO: TCXO input divide value (5 bits, 1 to 32)
- P1PLL: PLL primary post-divider value (4 to 9, 11, 13)
- PRTCXO: TCXO-DPLL FB prescaler divide value (2 to 17)
- INTTCXO: TCXO-DPLL FB divider integer value (30 bits, 1 to 230-1)
- NUMTCXO: TCXO-DPLL FB divider numerator value (40 bits, 0 to 240-1)
- DENTCXO: TCXO-DPLL FB divider denominator value (fixed, 240)
Equation 3 relates to the REF-DPLL:
Equation 3. f
VCO = (f
INx / R
INx) × P1
PLL × PR
REF × (INT
REF + NUM
REF/ DEN
REF)
where
- fINx: Reference input frequency (x = 0 to 3) or VCO loopback frequency (x = 4 or 5)
- RINx: Reference input divide value (16 bits, 1 to 216-1) (x = 0 to 5)
- PRREF: REF-DPLL FB prescaler divide value (2 to 17)
- INTREF: REF-DPLL FB divider integer value (30 bits, 1 to 230-1)
- NUMREF: REF-DPLL FB divider numerator value (40 bits, 0 to 240-1)
- DENREF: REF-DPLL FB divider denominator value (40 bits, 1 to 240)
Equation 4 relates to any reference inputs assigned to a DPLL reference mux to achieve a constant REF-TDC rate required for proper input switchover.
Equation 4. fREF-TDC = fIN0/RIN0 =fIN1/RIN1 = fIN2/RIN2 = fIN3/RIN3
Equation 5, Equation 6, Equation 7, Equation 8, and Equation 9 relate to the output frequency according to the output channel mux selection (CHxMUX).
Equation 5. fCHxMUX = fVCOy / PnPLLy when PLLy post-divider is selected
Equation 6. fCHxMUX = fXO when XO is selected (OUT0 or OUT1)
Equation 7. fCHxMUX = fTCXO/REF when TCXO or REF is selected (OUT0 or OUT1)
Equation 8. fOUTx = fCHxMUX / ODOUTx (OUT1 to OUT6)
Equation 9. f
OUTx = f
CHxMUX / (DIVA
OUTx × DIVB
OUTx) (OUT0 or OUT7 only)
where
- fCHxMUX: Output channel mux frequency (from PLL post-divider, XO, or TCXO/Ref Bypass mux)
- fTCXO/REF: TCXO, DPLL1 Ref, or DPLL2 Ref input frequency (selected by TCXO/Ref Bypass mux)
- fOUTx: Output clock frequency (x = 0 to 7)
- PnPLLy: PLLy P1 (primary) or P2 (secondary) post-divider value (4 to 9, 11, 13)
- ODOUTx: Output divide value (20 bits, 1 to 220-1)
- ODBOUTx: Output MSB divide value for OUT0 or OUT7 (11 bits, 1 to 211-1)