JAJSCX6B January 2017 – July 2019 LMK04610
PRODUCTION DATA.
PLL1 in LMK0461x is a very low bandwidth PLL. The PLL is a fully programmable, ultra-flexible design and is intended to be used for jitter cleaning of the noisy input clock. The PLL uses a semi-digital architecture and there is no need for external loop filter. The loop-filter has separated integral and proportional paths, which can be programmed individually to define the PLL transfer. There is a possibility to add higher order poles by connecting a capacitor outside the chip with a fixed on-chip resistor RCTRL. The block diagram of the PLL1 is shown in Figure 36. The PLL uses an external VCXO as a voltage controlled oscillator. Both positive and negative gain VCXOs are supported by LMK046xx.
To reduce lock time, PLL1 supports two locking modes which can be individually configured by the user. When configured, PLL1 starts with Fastlock (with very high integral gain) and after lock, it switches to desired integral gain.
PLL1 Bandwidth depends on the VCXO gain and loop parameters. LMK0461x PLLs are designed with active damping technique. For a given VCXO gain and divider settings, the bandwidth can be programmed by using the PLL1_PROP settings. The higher the value, the higher the bandwidth.
Table 13 shows the internal PLL1 parameter, register and programming ranges. Use the TICS Pro EVM tool to calculate PLL1_PROP, PLL1_PROP_LF, PLL1_INTG, and PLL1_INTG_LF values.