The MASH_SEED word can use the sigma-delta modulator to shift output signal phase with respect to the input reference. If a SYNC pulse is sent (software or pin) or the MASH is reset with MASH_RST_N, then this phase shift is from the initial phase of zero. The phase shift can be calculated based on the MASH_SEED.
Equation 4. Phase shift in degrees = 360 × ( MASH_SEED / PLL_DEN / CHDIV )
There are a few considerations with MASH_SEED:
- Phase shift can be done with a PLL_NUM = 0, but MASH_ORDER must be greater than zero.
- For MASH_ORDER = 1, the phase shifting only occurs when MASH_SEED is a multiple of PLL_DEN.
- Setting MASH_SEED > 0 can impact fractional spurs. If used with a PLL_NUM = 0, it can create fractional spurs. If used with a non-zero numerator, it can either help or hurt spurs and this effect can be simulated with the TI PLLatinum Sim tool.