L6981 datasheet(45/49 Pages) STMICROELECTRONICS

45 / 49 page

Contents

Diagram ...........................................................................2

Pin configuration ..................................................................3

Typical application circuit..........................................................4

Absolute maximum ratings ........................................................5

Electrical characteristics...........................................................6

Functional description .............................................................8

6.1

Enable ....................................................................... 8

6.2

Soft-start...................................................................... 9

6.3

Undervoltage lockout .......................................................... 10

6.4

Light-load operation ........................................................... 10

6.4.1

Low consumption mode (LCM) ............................................. 10

6.4.2

Low noise mode (LNM) ................................................... 14

6.4.3

Efficiency for Low consumption mode and Low noise mode part number ............. 15

6.4.4

Load regulation for low consumption mode and low noise mode part number.......... 16

6.5

Overvoltage protection ......................................................... 16

6.5.1

Low consumption mode part number ........................................ 17

6.5.2

Low noise mode part number .............................................. 18

6.6

Overcurrent protection ......................................................... 18

6.7

Thermal shutdown............................................................. 20

Closing the loop ..................................................................21

7.1

GCO(s) control to output transfer function ......................................... 21

7.2

Error amplifier compensation network ............................................ 22

7.3

Voltage divider ................................................................ 23

Design of the power components .................................................24

8.1

Programmable power up threshold ............................................... 24

8.2

External synchronization (only available for Low Noise Mode) ........................ 24

8.3

Output voltage adjustment ...................................................... 25

8.4

Design of the power components ................................................ 26

8.4.1

Input capacitor selection .................................................. 26

L6981

Contents

DS13554 - Rev 1

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