A7987 datasheet(32/36 Pages) STMICROELECTRONICS

32 / 36 page

Contents

Application schematic .............................................................2

Block diagram .....................................................................3

Pin settings........................................................................4

3.1

Pin connection ................................................................. 4

3.2

Pin description ................................................................. 4

3.3

Maximum ratings ............................................................... 5

3.4

Thermal data .................................................................. 5

3.5

ESD protection ................................................................ 5

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

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

5.1

Oscillator and synchronization.................................................... 8

5.2

Soft-start..................................................................... 10

5.3

Error amplifier and light-load management ........................................ 12

5.4

Low VIN operation............................................................. 12

5.5

Overcurrent protection ......................................................... 12

5.6

Overtemperature protection ..................................................... 14

Application information ...........................................................15

6.1

Input capacitor selection........................................................ 15

6.2

Output capacitor selection ...................................................... 15

6.3

Inductor selection ............................................................. 16

6.4

Compensation network......................................................... 16

6.4.1

Type II compensation network.............................................. 18

6.4.2

Type III compensation network ............................................. 19

6.5

Thermal considerations ........................................................ 21

6.6

Layout considerations.......................................................... 22

Demonstration board .............................................................23

Application ideas .................................................................26

8.1

Positive buck-boost............................................................ 26

8.2

Negative buck-boost ........................................................... 27

A7987

Contents

DS12928 - Rev 3

page 32/36

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