A6986I datasheet(57/62 Pages) STMICROELECTRONICS

57 / 62 page

Contents

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

Pin connection ....................................................................3

2.1

Maximum ratings ............................................................... 4

Electrical characteristics...........................................................5

Parameters over the temperature range ............................................8

Functional description .............................................................9

5.1

Primary side ................................................................... 9

5.1.1

Power supply and voltage reference ......................................... 10

5.1.2

Switchover feature ...................................................... 11

5.1.3

Voltage monitor ......................................................... 11

5.1.4

Error amplifier .......................................................... 11

5.2

Transformer .................................................................. 11

5.3

Secondary side ............................................................... 11

5.4

Iso-buck operation principle ..................................................... 12

5.5

Soft-start and inhibit ........................................................... 13

5.6

Minimum on-time.............................................................. 15

5.7

Output voltage line regulation ................................................... 17

5.8

Output voltage load regulation................................................... 19

5.9

Overcurrent protection ......................................................... 20

5.10

Overvoltage protection ......................................................... 22

5.11

Thermal shutdown............................................................. 23

Closing the loop ..................................................................24

6.1

GCO(s) control to output transfer function ......................................... 24

6.2

Error amplifier compensation network ............................................ 25

6.3

Voltage divider ................................................................ 26

6.4

Total loop gain ................................................................ 26

6.5

Compensation network design .................................................. 27

Application notes .................................................................29

7.1

Output voltage adjustment ...................................................... 29

A6986I

Contents

DS13481 - Rev 2

page 57/62

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