SLVSH09A November 2023 – June 2024 TPS6522005-EP
PRODUCTION DATA
The bucks provide a digital spread spectrum which reduces the EMI of the power supply over a wide frequency range. Setting BUCK_SS_ENABLE to 1 enables the spread spectrum on all three bucks. Spread Spectrum is only applicable if the bucks are configured for fixed frequency, BUCK_FF_ENABLE set to 1. The internal modulator dithers the internal clock when the spread spectrum is enabled.
DRSS (a) combines a low-frequency triangular modulation profile (b) with a high frequency cycle-by-cycle random modulation profile (c). The low frequency triangular modulation improves performance in lower radio frequency bands (for example, the AM band), while the high frequency random modulation improves performance in higher radio frequency bands (for example, the FM band). In addition, the frequency of the triangular modulation is further modulated randomly to reduce the likelihood of any audible tones. To minimize output voltage ripple caused by spread spectrum, duty cycle is modified on a cycle-by-cycle basis to maintain a nearly constant duty cycle when dithering is enabled. See Figure 6-4 as an example of the modulation.