SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The DPLL_HDMI uses instance of the DPLL module of type B. For information regarding DPLL types, see PRCM.
Figure 13-17 shows the internal reference diagram of the DPLL_HDMI and PLLCTRL_HDMI interconnection in the device.
Figure 13-17 DPLL_HDMI and PLLCTRL_HDMI Reference DiagramFigure 13-18 shows a simplified block diagram of the DPLL instance used for the DPLL_HDMI.
Figure 13-18 DPLL_HDMI Functional Block DiagramThe DPLL input clock CLKINP goes to a predivider N + 1. The entire loop runs on the REFCLK clock after this predivider. The value of N + 1 is controlled through the PLLCTRL_HDMI_CONFIGURATION1[8:1] PLL_REGN bit field. The CLKINP range is 0.62 to 60MHz. The REFCLK range is 0.62 to 2.5MHz.
The output clock CLKDCOLDO is synthesized by a digitally controlled oscillator (DCO block). The CLKDCOLDO frequency can be given with CLKDCOLDO = CLKINP × M/(N + 1). For this purpose, the feedback multiplier M must be configured through the PLLCTRL_HDMI_CONFIGURATION1[20:9] PLL_REGM bit field. The frequency range of the DCO must be selected via the PLLCTRL_HDMI_CONFIGURATION2[3:1] PLL_SELFREQDCO register bit-field depending on the CLKDCOLDO frequency.
The DPLL module supports fractional synthesis. That is, the frequency multiplication factor M can be programmed as fractional. This is done through the use of a sigma-delta feedback divider (M). A fractional value (REGM.f ) of 18 bits is supported, thereby enabling control for better accuracy. Programming the fractional value is done by setting the PLLCTRL_HDMI_CONFIGURATION4[17:0] PLL_REGM_F bit field. Fractional synthesis is not supported for M > 4093. For integer only division the PLL_REGM_F bit-field must be set to 0x00000.
The programming of the sigma-delta feedback divider is mandatory to get the optimal jitter performance. The value is determined by PLL_SD = ceiling ((M/(N + 1)) × CLKINP/250), and can be programmed into the PLLCTRL_HDMI_CONFIGURATION3[17:10] PLL_SD register bit-field.
The DPLL provides also control for the loop bandwidth (BW). The BW can be increased or decreased by programming the [18] PLL_HDMI_LOOPBW_INCR_DECRZ and [17:16] PLL_HDMI_LOOPBW bit-fields of the CTRL_CORE_DSS_PLL_CONTROL register in the device Control Module. This allows better control over the jitter at lower M values. [New DRA7xxP feature versus DRA75x/DRA74x]