SNAS805 June 2020 LMK61E08
PRODUCTION DATA.
The LMK61E08 features a fully integrated loop filter for the PLL that supports programmable loop bandwidth from 100 kHz to 1 MHz. The loop filter components, R2, C1, R3, and C3, can be configured by programming R36, R37, R38, and R39, respectively. The LMK61E08 features a fixed value of C2 of 10 nF. When the PLL is configured in fractional mode, R35[2] should be set to 1. When the reference doubler is disabled for integer mode PLL, R35[2] should be set to 0 and R38[6:0] should be set to 0x00. When the reference doubler is enabled for integer mode PLL, R35[2] should be set to 1 and R38 and R39 are written with the appropriate values. Figure 25 shows the loop filter structure of the PLL. It is important to set the PLL to the best possible bandwidth to minimize output jitter.