SNAS750B November 2020 – March 2021 LMK5C33216
PRODUCTION DATA
The APLL fractional N divider includes a 12-b integer portion (INT), a 40-b numerator portion (NUM), a fixed 40-b or a programmable 24-b denominator portion (DEN), and a sigma-delta modulator. The INT and NUM are programmable. When an APLL works with a DPLL in a loop, APLL can use fixed 40-bit for very high frequency resolution on the VCO clock. When the APLL works in an independent loop, like APLL1 and APLL2 in Figure 9-6or APLLs in Figure 9-7, 24-bit programmable denominator is recommended. The total APLL N divider value is: N = INT + NUM / 240 or INT + NUM / 224.
In APLL free-run mode, the PFD frequency and total N divider for APLL determine the VCO frequency, which can be computed with 24-b denominator by Equation 2.