The Si5118 is a SmartClock synthesizer, intended for automotive electronics applications where health monitoring and fault detection functions of a reference clock are needed between a frequency source and the intended endpoint. FPGAs, SoCs, and ASICs often include on-chip PLLs for frequency synthesis, and can often be supplied to other endpoints within a system design. Si5118 monitors the health of those clocks, can output fault detection flags, and migrate to a redundant backup reference source if a fault is detected on the primary source. In the event of both primary input reference and backup redundant crystal reference frequencies fail, Si5118 enters into AlwaysOn mode to allow the output clocks to continue operating within +/-5% of the output frequency, enabling the system to continue sourcing reference clocks while entering a safe state.
The Si5118 is capable of taking three input reference sources: a primary clock generated by an external source (such as a crystal oscillator, FPGA, SoC), a backup crystal reference source, and a feedback reference source from one of the SI5118 outputs. All three input sources must be the same frequency. The device actively monitors the health of the primary reference input source using the SmartClock out of frequency (FOOF) monitors, and provides up to 7 reference clock outputs of the same frequency that can be supplied to various endpoints within the system design.
If a FOOF fault is detected on the primary input reference clock, the device communicates an output signal flag to an external microcontroller or system safety manager. To ensure the Si5118 output clocks continue to run uninterrupted, the microcontroller or system safety manager can instruct the Si5118 to change the input reference source from the primary clock source to the backup crystal source using the CLK_SEL pins. Should the backup crystal reference source also fault, the device will again communicate the failure to the external microcontroller or system safety manager, and then will enter AlwaysOn mode. AlwaysOn mode allows the output clocks to continue operating within +/-5% of the output frequency, enabling the system to continue sourcing reference clocks even though the primary and backup sources have faulted.
SKYWORKS SI5118AA13325-AM2R