Power, Reset, and Clock Management
Modulation frequency (f
m
) can be programmed as a ratio of Fref / 4; that is, the value that needs to be
programmed ModFreqDivider = Fref / (4*f
m
). The ModFreqDivider is split into Mantissa and 2^Exponent
(ModFreqDivider = ModFreqDividerMantissa * 2^ModFreqDividerExponent). The mantissa is controlled by
7-bit signal ModFreqDividerMantissa through
CM_SSC_MODFREQDIV_DPLL_xxx.MODFREQDEV_MANTISSA bit field. The exponent is controlled by
3bit signal ModFreqDividerExponent through the
CM_SSC_MODFREQDIV_DPLL_xxx.MODFREQDEV_EXPONENT bit field.
Note: Although the same value of ModFreqDivider can be obtained by different combinations of mantissa
and exponent values, it is recommended to get the target ModFreqDivider by programming maximum
mantissa and a minimum exponent. To define the Frequency spread (
Δ
f),
Δ
M must be controlled as
explained previously. To define
Δ
M, the step size of M for each Fref during the triangular pattern must be
programmed; that is,
Δ
M = (2^ModFreqDividerExponent) * ModFreqDividerMantissa * DeltaMStep IF
ModFreqDividerExponent
≤
3
Δ
M = 8 * ModFreqDividerMantissa * DeltaMStep IF
ModFreqDividerExponent > 3
DeltaMStep is split into integer part and fractional part. Integer part is controlled by 2-bit signal
DeltaMStepInteger through the CM_SSC_DELTAMSTEP_DPLL_xxx.DELTAMSTEP_INTEGER bit field.
Fractional part is controlled by 18-bit signal DeltaMStepFraction through the
CM_SSC_DELTAMSTEP_DPLL_xxx.DELTAMSTEP_FRACTION bit field.
The frequency spread achieved has an overshoot of 20 percent or an inaccuracy of +20 percent. If the
CM_CLKMODE_DPLL.DPLL_SSC_DOWNSPREADis set to 1, the frequency spread on lower side is
twice the programmed value. The frequency spread on higher side is 0 (except for the overshoot as
described previously).
There is restriction of range of M values. The restriction is M-
Δ
M should be
≥
20. Also, M+
Δ
M should be
≤
2045. In case the downspread feature is enabled, M-2*
Δ
M should be
≥
20 and M
≤
2045.
8.1.6.7
Core PLL Description
The Core PLL provides the source for a majority of the device infrastructure and peripheral clocks. The
Core PLL comprises an ADPLLS with HSDIVIDER and additional dividers and muxes located in the
PRCM as shown in
524
Power, Reset, and Clock Management (PRCM)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated