The DPLL_USB_OTG_SS factors must be calculated based on the required input and output frequencies, keeping the PLL internal reference frequency (REFCLK) in the appropriate range (0.62 to 2.5 MHz).
- REGM factor is programmed in the DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION1[20:9] PLL_REGM bit field.
- Fractional part of REGM factor is programmed in the DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION4[17:0] PLL_REGM_F bit field.
- REGN factor is programmed in the DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION1[8:1] PLL_REGN bit field.
- DCO frequency range is set in the DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION2[3:1] PLL_SELFREQDCO bit field.
- PLL_SELFREQDCO should be set to 0x2 if 750 MHz < CLKDCOLDO [MHz] < 1500 MHz.
- PLL_SELFREQDCO should be set to 0x4 if 1250 MHz < CLKDCOLDO [MHz] < 2500 MHz.
- SD divider is programmed in the DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION3[17:10] PLL_SD bit field. The DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION2[3:1] PLL_SELFREQDCO register bit field should be programmed depending on the value of CLKDCOLDO = CLKINP × M/(N + 1).
Figure 26-14 shows the formulae and programming sequence.
Note: - The equation for USB3_PHY_TX/USB3_PHY_RX (MHz) applies to the CLKDCOLDO of the DPLL_USB_OTG_SS.
- CLKDCOLDO output frequency of the DPLL_USB_OTG_SS should be programmed to 2.5 GHz, for the super-speed USB (5 Gbps) mode.
Table 26-14 summarizes the registers for the DPLLCTRL_USB_OTG_SS programming sequence.
Table 26-14 Register Call Summary for USB3_PHY PLL Programming Sequence