Silicon Laboratories SI5375 - Manual (Page 33)

Si53xx-RM
Rev. 1.2 33
4. DSPLL (All Devices)
All members of the Any-Frequency Precision Clocks family incorporate a phase-locked loop (PLL) that utilizes
Silicon Laboratories' third generation DSPLL technology to eliminate jitter, noise, and the need for external VCXO
and loop filter components found in discrete PLL implementations. This is achieved by using a digital signal
processing (DSP) algorithm to replace the loop filter commonly found in discrete PLL designs. Because external
PLL components are not required, sensitivity to board-level noise sources is minimized. This digital technology
provides highly stable and consistent operation over process, temperature, and voltage variations.
A simplified block diagram of the DSPLL is shown in Figure 18. This algorithm processes the phase detector error
term and generates a digital frequency control word M to adjust the frequency of the digitally-controlled oscillator
(DCO). The narrowband configuration devices (Si5316, Si5319, Si5323, Si5324, Si5326, Si5327, Si5366, Si5368,
and Si5369) provide ultra-low jitter generation by using an external jitter reference clock and jitter attenuation. For
applications where basic frequency multiplication of low jitter clocks is all that is required, the wideband parts
(Si5322, Si5325, Si5365, and Si5367) are available.
Figure 18. Any-Frequency Precision Clock DSPLL Block Diagram
f
IN
DSPLL
Phase
Detector
Digital
DCO
Digital Loop
Filter
Fvco
M
f
OUT