AN3392 datasheet(13/57 Pages) STMICROELECTRONICS

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AN3392

Output voltage ripple

Doc ID 018749 Rev 1

13/57

Output voltage ripple

Assuming a resistive load, the output voltage ripple is directly related to the output current

ripple.

In a single-ended architecture, the output current is the current flowing on the inductor when

it recirculates through the rectifiers. Referring to Figure 6, the larger the inductance, the

smaller the current ripple (Ib-Ia).

In IL-4 architecture, output current is the sum of the four currents flowing in each inductor.

Even if the current on each branch is the same as in the single-ended architecture, the

TSW/4 shift between the driving signals implies that output current has a small amount of

ripple. Figure 11 shows both the current in each branch and the final IOUT.

Figure 11.

Step-up current waveforms or interleaved 4-phase architecture

With respect to single-ended architecture, input and output current ripple are significantly

reduced due to both the split of the incoming current in the four branches and the related

phase shift.

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