VIPer01

General description

DocID028751 Rev 1

19/36

4.5

Soft-start

The internal soft-start function of the device progressively increases the cycle-by-cycle

internally set at 8 ms. This function is activated at any attempt of converter startup and at

any restart after a fault event. The feature protects the system at the startup when the

output load occurs like a short-circuit and the converter works at its maximum drain current

limitation.

Figure 27: Soft startup

4.6

Oscillator

The IC embeds a fixed frequency oscillator with jittering feature. The switching frequency is

to get a spread-spectrum action that distributes the energy of each harmonic of the

switching frequency over a number of frequency bands, having the same energy on the

whole but smaller amplitudes. This helps to reduce the conducted emissions, especially

when measured with the average detection method or, which is the same, to pass the EMI

tests with an input filter of smaller size than that needed in absence of jittering feature.

type) and 120 kHz (H type).

4.7

Pulse-skipping

The IC embeds a pulse-skip circuit that operates in the following ways:



cycle is skipped. The cycles can be skipped until the minimum switching frequency is



cycle is restored. The cycles can be restored until the nominal switching frequency is