M31 Crystal Free Technology


M31 Crystal Free Technology allows PHY to operate without the existence of external crystal oscillator or input reference clock.

M31 USB PHY with BCK (Build-in-Clock) module processes background calibration during USB data transfer to ensure the internal clock frequency accuracy. The IP can meet IF-compliance spec and exhibit the same electrical performance as the standard USB IP.

The BCK module embedded in M31 PCIe PHY provides a handshake mechanism between PHY and controller to enter/exit L1 PM sub-states. Whether the IP acts as RC or EP, the system can turn-off the reference clock to PHY during this low-power mode.

The BCK module embedded in M31 MIPI M-PHY is used for initial internal circuit calibration and PWM communications. The BCK module also detects the existence of input reference clock from UFS host, the IP can switch between external and internal reference clocks and enter/exit different operation state smoothly.


  • USB PHY with BCK fully compliant with Universal Serial Bus USB3.2 Gen1X1, USB2.0 and USB1.1 electrical specifications
  • USB PHY with BCK supports clock outputs from internal BCK module
  • USB PHY with BCK supports real-time calibrations to assure the frequency accuracy (±500ppm during data transfer).
  • PCIe PHY embedded BCK supports L1 PM sub-states control without the existence of reference clock from system or external pads
  • MIPI M-PHY embedded BCK supports PWM communication and external reference clock detection in UFS device mode