AN4158 datasheet(18/34 Pages) STMICROELECTRONICS

Il numero della parte	AN4158

Spiegazioni elettronici	Peak current control with automatic decay adjustment

PDF	34 Pages

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Produttore elettronici	STMICROELECTRONICS [STMicroelectronics]

Homepage	http://www.st.com

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18 / 34 page

Peak current control with PWM and constant off-time

AN4158

18/34

DocID023635 Rev 2

Equation 8

When the current drop

IphOFF becomes lower than IphON,Min, the stability equation can no

longer be satisfied and the current control fails. The current starts to increase until stability is

restored (it is possible because

IphOFF increases with the current) and the actual peak

current is different than the target one. The minimum on-time limit is usually reached at low

target currents, motor windings with a high LPh/RPh ratio, and when slow decay is used

during the off-time.

Figure 13. Peak current control unstable

Figure 12. Minimum on-time

sense

Reference current

comm

PhON,Min

AM15114v1

I

VBUS LPh tcomm





OFF

Target

IPeak

comm

OFF

comm

OFF

comm

OFF

comm

OFF

comm

IPhOFF =

PhONMin

AM15115v1

AN4158 Scheda tecnica(PDF) 18 Page - STMicroelectronics