L5988D datasheet(22/52 Pages) STMICROELECTRONICS

22 / 52 page

Functional description

L5988D

22/52

DocID15324 Rev 4

The typical active thresholds in case of ILIM-ADJ pin left floating are IPEAK_TH = 4.0 A,

IVALLEY_TH = 4.7 A. The dimensioning of the pull up resistor versus VREF to decrease the

peak (and valley) thresholds follows the formula:

Equation 8

In the same way the pull down resistor is selected using the following formula to increase

the maximum current thresholds:

Equation 9

Figure 11. Constant current protection at extreme duty cycles

R9 



1.2



4.0 IPEAK_TH

–

-------------------------------------

R3 



2.706



IPEAK_TH 4.0

–

-------------------------------------

Valley current limit

skipped switching pulses

Constant current protection

during soft start time

soft start time

ZOOM

HICCUP protection

Is triggered at the

end of the SS time

Valley current limit

skipped switching pulses

Constant current protection

during soft start time

soft start time

ZOOM

HICCUP protection

Is triggered at the

end of the SS time

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