1. Functional Description
1.1 DSPLL
The DSPLL provides the synthesis for generating the output clock frequencies which are synchronous to the selected input clock
frequency or free run from the reference clock. It consists of a phase detector, a programmable digital loop filter, a high-performance
ultra-low-phase-noise analog VCO, and a user configurable feedback divider. Use of an external XO provides the DSPLL with a stable
low-noise clock source for frequency synthesis and for maintaining frequency accuracy in the free run or Holdover modes. No other
external components are required for oscillation. A key feature of DSPLL is providing immunity to external noise coupling from power
supplies and other uncontrolled noise sources that normally exist on printed circuit boards.
The frequency configuration of the DSPLL is programmable through the SPI or I
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C serial interface and can also be stored in non-vola-
tile memory (NVM) or RAM. The combination of input dividers (P0-P3), frequency multiplication (M), output division (N), and output
division (R0A-R9A) allows the generation of a wide range of frequencies on any of the outputs. All divider values for a specific
frequency plan are easily determined using the ClockBuilder Pro software.
1.2 LTE Frequency Configuration
The device’s frequency configuration is fully programmable through the serial interface and can also be stored in non-volatile memory.
The flexible combination of dividers and a high frequency VCO allows the device to generate multiple output clock frequencies for
applications that require ultra-low phase-noise and spurious performance. The table below shows a partial list of possible output
frequencies for LTE applications. The Si5386's DSPLL core can generate up to five asynchronous frequencies. These frequencies are
distributed to the output dividers using a configurable crosspoint mux. The output R dividers allow further division for up to 12 unique
integer-related frequencies on the Si5386. The ClockBuilder Pro software utility provides a simple means of automatically calculating
the optimum divider values (P, M, N and R) for the frequencies listed below. In addition to the LTE frequencies, the Si5386 device can
simultaneously generate wireline clocks like 156.25 MHz, 155.52 MHz, 125 MHz, etc. and system clocks like 100 MHz, 33 MHz, 25
MHz, etc.
Si5386 Rev. E Reference Manual • Functional Description
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.2 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • December 9, 2021
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