SPRUI33H November 2015 – June 2024 TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1
There are two settings to configure for the PLL – a multiplier and a divider. The settings obey the formula:
fPLLSYSCLK = fOSCCLK * (SYSPLLMULT.IMULT + SYSPLLMULT.FMULT) / (SYSPLLMULT.ODIV * SYSCLKDIVSEL.PLLSYSCLKDIV)
where fOSCCLK is the system oscillator clock frequency, IMULT and FMULT are the integral and fractional parts of the multipliers, ODIV is the PLL output divider, and PLLSYSCLKDIV is the system clock divider. For the permissible values of the multipliers and dividers, see the documentation for the respective registers.
Many combinations of multiplier and divider can produce the same output frequency. However, the product of the reference clock frequency and the multiplier (known as the VCO frequency) must be in the range specified in the data manual f(VCO) parameter. The VCO frequency divided by the output divider (known as the PLL output frequency) must be in the range specified by the TMS320F28004x Real-Time Microcontrollers Data Sheet f(PLLRAWCLK) parameter. The following examples use 120MHz to 200MHz for this parameter.