L6982 datasheet(10/48 Pages) STMICROELECTRONICS

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Figure 6. Soft-start phase with ROUT = 3 Ω

6.3

Undervoltage lockout

The device implements the undervoltage lockout (UVLO) continuously sensing the voltage on the VCC pin, if the

UVLO lasts more than 10 μs, the internal logic resets the device by turning off both LS and HS.

After the reset, if the EN pin is still high, the device repeats the soft-start procedure.

6.4

Light-load operation

The L6982 implements two different light load strategies:

Low consumption mode (LCM).

Low noise mode (LNM).

Please refer to Table 11 to select the part number with the preferred light load strategy.

6.4.1

Low consumption mode (LCM)

The LCM maximizes the efficiency at light-load.

When the switch peak current request is lower than the ISKIP threshold (please refer to Table 6), the device

regulates VOUT by the skip threshold. The minimum voltage is given by:

VOUT, LCM= VFB, LCM∙RPH+RPL

RPL

(1)

Where VFB, LCM is 1.8% (typ.) higher than VFB.

The device interrupts the switching activities when two conditions happen together:

The peak inductor current required is lower than ISKIP.

The voltage on the FB pin is higher than VFB, LCM.

L6982

Undervoltage lockout

DS13683 - Rev 1

page 10/48

L6982 数据表(PDF) 10 Page - STMicroelectronics