AN4158 datasheet(32/34 Pages) STMICROELECTRONICS

No. de pieza	AN4158

Descripción Electrónicos	Peak current control with automatic decay adjustment

PDF	34 Pages

Scroll/Zoom	100%

Fabricante Electrónico	STMICROELECTRONICS [STMicroelectronics]

Página de inicio	http://www.st.com

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32 / 34 page

Setup and optimization

AN4158

32/34

DocID023635 Rev 2

Figure 27. High FAST_STEP value example

Figure 28. Low FAST_STEP value example

5.2

Predictive current control

When the predictive current control is used, two more parameters need to be set: the target

switching time TSW and the minimum off-time TOFF_MIN.

The TSW parameter is equivalent to the TOFF parameter described in Section 5.1.2 and it

should be set according to the same considerations.

The TOFF_MIN limits the variation of the off-time imposing its minimum value. It is

equivalent to the TOFF parameter described in Section 5.1.2 and it should be set according

to the following golden rules:



TOFF_MIN < TSW



TOFF_MIN > TOFF_FAST



TOFF_MIN + 2 x TON_MIN > 1/fSW,max, where fSW,max is the maximum allowed

switching frequency of the system.

100 %

0 %

Current reference

FAST_STEP / 4

FAST_STEP

Deep current undershoot

in the first microsteps

AM15128v1

100 %

0 %

Current reference

FAST_STEP / 4

FAST_STEP

Long fast decay sequence is

required to reach target current

AM15129v1

AN4158 Datasheet(PDF) 32 Page - STMicroelectronics