SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
Idle-bypass fast relock mode is not supported for DPLL_USB_OTG_SS.
DPLL_USB_OTG_SS supports idle-bypass low-power mode. A transition from a normal operation to idle-bypass mode is performed when software sets the DPLLCTRL_USB_OTG_SS.DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION2[0] PLL_IDLE bit to 0x1. IDLE signal assertion triggers a power-down sequence on DPLL internal LDO analog blocks and the DCO oscillator.
In idle-bypass low-power mode, the PHASELOCK and FREQLOCK output signals are asserted low and CLKDCOLDO goes low. Also, the internal reference clock REFCLK = CLKINP/N + 1 is gated inside the DPLL digital control logic to save power.
In the functional mode, the DPLL_USB_OTG_SS.TICOPWDN output indicates to the PLL controller the status of the power-down signal (active high) of the internal DCO oscillator. The internal DCO oscillator is powered down in idle-bypass mode or during period from SYSRESETN 0->1 to module initialization. The DCO oscillator exits power-down (TICOPWDN goes low) whenever the module internally tries to lock/relock after initialization or exiting idle-bypass mode.
In the functional mode, DPLL_USB_OTG_SS.LDOPWDN output indicates to the PLL controller the status of the power-down signal (active high) of the internal LDO. LDOPWDN goes high as soon as the internal LDO is powered down. LDOPWDN goes low after the LDO output voltage is stable. The internal LDO is powered down in the period from SYSRESETN 0 → 1 to module initialization or when entering into idle-bypass mode. LDOPWDN is cleared whenever the module internally tries to lock/relock after initialization or exiting idle-bypass mode after the internal LDO output voltage has stabilized.
The DCO and LDO power ON and OFF states are reflected within the read-only DPLLCTRL_USB_OTG_SS.PLL_STATUS[16] PLL_TICOPWDN and DPLLCTRL_USB_OTG_SS.PLL_STATUS[15] LDOPWDN monitor bits.
To exit idle-bypass mode and restore clock generation, the user should write DPLLCTRL_USB_OTG_SS.PLL_CONFIGURATION2[0] PLL_IDLE to 0x0, which deasserts the IDLE signal, and DPLL_USB_OTG_SS automatically enters a relock sequence. CLKDCOLDO output clock is activated after the FREQLOCK or the PHASELOCK signal goes high, depending on selected locking criteria.