The SI570 & SI571 series from Silicon Labs are programmable oscillators(XO) & Voltage Controlled Oscillators (VCXO) which are programmed via an I2C serial interface.
You can find the I2C address information for your part number from this link:
https://www.silabs.com/timing/lookup-customize
As an example, for 570FAB000544DG, the I2C address (Hex Format) is 0x5D