Skyworks Si5338 - Configuring Initial Phase Offset and Phase Step Size; Initial Phase Offset; Phase Step Size

Si5338-RM
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7. Configuring Initial Phase Offset and Phase Step Size
7.1. Initial Phase Offset
Each output of the Si5338 can be programmed with an independent initial phase offset. The phase offset
parameter is represented as a 2s complement integer and is calculated as follows:
Equation 4. Phase Offset
Make sure to convert MSx_PHOFF to a 2s complement number if a negative value is required. The initial phase
offset adjustment has a range of ±45 ns. For the initial phase offset to work properly, the R divider must be set to 1.
A soft reset must be applied for the phase offset value to take effect.
7.2. Phase Step Size
Additionally, each output can have its phase stepped up and down in predefined steps. The phase step size has an
inc/dec range of ±45 ns and an accuracy of better than 20 ps. The phase step convention is that a positive value
will delay the output in time. A phase step increment or decrement is controlled by the Pinc/Pdec pins or register
bits. See bits [1:0] of Registers 52, 63, 74, and 85 for more information. The phase step size register parameter is
an unsigned integer calculated as follows:
Equation 5. Phase Inc/Dec
MSx_PHOFF Round Phase Offset in Seconds128 Fvco
Where: Fvco is in Hz
=
MSx_PHSTEP Round Desired Phase Step Size in seconds128 Fvco
Where: Fvco is in Hz
=