Spread spectrum
S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021
10
NXP Semiconductors
Figure 14. VCO frequency out of specified range
5. Spread spectrum
Spread Spectrum clocking is a technique used in electronic design to intentionally modulate the ideal
position of the clock edge such that the resulting signal’s spectrum is “spread” around the ideal
frequency of the clock. Spread Spectrum clocking is often used to help meet the regulated EMI
requirements.
This section provides the user instructions on how to enable Spread Spectrum functionality.
For S32G2, Spread Spectrum clock modulation is only available for the Core, Accelerator and DDR
PLLs.
PLL operates in frequency modulation mode when the user sets the following bits as shown in the table
below –
Table 3. Mode to enable spread spectrum
PLLCR[PLLPD]
PLLFD[SDMEN]
PLLFM[SSCGBYP]
PLLFM[SPREADCTL]
0
1
0
0
5.1
Frequency modulation programming
Modulation depth and modulation frequency programming uses step number (PLLFM[STEPNO]) and
step size (PLLFM[STEPSIZE]) which can be calculated by using the below equations:
𝑃𝐿𝐿𝐹𝑀[𝑆𝑇𝐸𝑃𝑁𝑂] =
𝑓
REF
2 × 𝑓
MOD
× 𝑃𝐿𝐿𝐷𝐼𝑉[𝑅𝐷𝐼𝑉]
Equation 1
